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Topic One[Cont'd]
Define of terms used in Anatomy and Physiology
Anatomy: the word anatomy is derived from a Greek word “Anatome” meaning to cut up. It is the study of structures that make up the body and how those structures relate with each
other.The study of anatomy includes many sub specialties. These are Gross anatomy, Microscopic anatomy, Developmental anatomy and Embryology.
Gross anatomy studies body structure with out microscope.Systemic anatomy studies functional relationships of organs within a system whereas Regional anatomy studies body part regionally. Both systemic and regional approaches may be used to study gross anatomy
Microscopic anatomy (Histology) requires the use of microscope to study tissues that form the various organs of the body.
Physiology: the word physiology derived from a Greek word for study of nature. It is the study of how the body and its part work or function.
Homeostasis
When structure and function are coordinated the body achieves a relative stability of its internal environment called homeostasis / staying the same. Although the external environmental changes constantly, the internal environment of a healthy body remains the same with in normal limits.
Under normal conditions, homeostasis is maintained by adaptive mechanisms ranging from control center in the brain to chemical substances called hormones that are secreted by
various organs directly into the blood streams. Some of the functions controlled by homeostasis mechanisms are blood pressure, body temperature, breathing and heart rate.
Level of structural organization of the body
The human body has different structural levels of organization, starting with atoms molecules and compounds and increasing in size and complexity to cells, tissues, organs and the systems that make up the complete organism.
Atoms molecules and compounds: - At its simplest level,the body is composed of atoms. The most common elements in living organism are carbon, hydrogen, oxygen, nitrogen phosphorus and sulfur.
Cell: The smallest independent units of life. All life depends on the many chemical activities of cells. Some of the basic functions of cell are: growth, metabolism, irritability and reproduction.
Tissue: tissue is made up of many similar cells that perform a specific function. The various tissues of the body are divided in to four groups. These are epithelial, connective, nervous and muscle tissue
Organ: - Is an integrated collection of two or more kinds of tissue that works together to perform specific function. For example: Stomach is made of all type of tissues
System: Is a group of organs that work together to perform major function. For example: Respiratory system contains several organs.
Organism level: - The various organs of the body form the entire organism.
Anatomical Positions.
Anatomical positions are universally accepted as the starting points for positional references to the body. In anatomical position the subject is standing erect and facing the observer, the feet are together, and the arms are hanging at the sides with the palms facing forward.
Relative Directional terms
Standardized terms of reference are used when anatomists describe the location of the body part. Relative means the location of one part of the body is always described in relation to another part of the body.
Body parts Regions
The body can generally be described to have areas of:
Axial body part: - It is the part of the body near the axis of the body. This includes head, neck, thorax (chest), abdomen,and pelvis.
Appendicular body part: - It is the part of the body out of the axis line. This includes the upper and lower extremities.It is customary to subdivide the abdominal area into nine regions or more easily in to four quadrants.
Body planes and sections
Body planes are imaginary surfaces or planes lines that divide the body in to sections. This helps for further identification of specific areas.
Sagittal plane:
Divides the body into right and left half.
Mid sagittal plane: - divides body into equal left and right halves.
Para sagittal plane: - divides body into unequal left and right
Frontal plane: - divides the body into asymmetrical antererior and posterior sections.
Transverse plane: - divides the body into upper and lower body section.
Oblique plane: - divides the body obliquely into upper and lower section.
Body Cavities
The cavities of the body house the internal organs, which commonly referred to as the viscera. The two main body cavities are the larger ventral (anterior) and the smaller, dorsal (posterior) body cavity.
The ventral body cavity constitutes the thoracic cavity and the abdomino-pelvic body cavity.
The Thoracic cavity houses lung and heart. It is protected by the rib cage & associated musculature and the sternum anteriorly. It consists of the right and left pleural cavities and mediastinum (the portion of tissues and organs that separates the left and right lung).
Abdomino-pelvic Cavity extends from the diaphragm inferior to the floor of the pelvis. It is divided into superior abdominal and inferior pelvic cavity by imaginary line passing at upper pelvis.
Abdominal cavity contains the stomach, intestine, liver, spleen and gallbladder.
The pelvic cavity contains urinary bladder, rectum, and portions of the reproductive organs.
The dorsal body cavity: it constitutes the cephalic cavity containing brain and the vertebral canal containing the spinal cord.
TOPIC TWO
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Topic Two[Cont'd]
Cell is the basic living structural and functional unit of the body.
Cytology: - It is a branch of science concerned with a study of cells
Cell Theory states that :
a) All living organisms are composed of cell and cell products.
b) Cell is the basic unit of structure & function of all living organisms.
c) All cells come from the division of pre existing cell.
d) An organism as a whole can be understood through the collective activities & interactions of its cells.
To know more about cell, we can divide the cell in to four principal parts: -
Plasma (cell) membrane: it is the outer lining, limiting membrane separating the cell internal parts from extra cellular materials & external environment.
Cytoplasm: cytoplasm is the substance that surrounds organelles and is located between the nucleus and plasma membrane
Organelles: these are permanent structures with characteristic morphology that are highly specialized in specific cellular activity.
Inclusions: they are the secretions and storage products of cells.
Extra cellular materials are also referred to as the matrix, which are substances external to the cell surface.
Plasma Membrane
Plasma membrane is a thin outer membrane, which maintains the integrity of the cell. It keeps the cell and its contents separate and distinct from the surrounding. It is a double layered measuring about 4.5 nm and made of phospholipids,cholesterol, glyco-lipid, & carbohydrate (oligosaccharides).The bi-layer is self-sealing. If a needle is injected and pulled out, it automatically seals.
Functions: -
1. Separate the cytoplasm inside a cell from extra cellular fluid.
2. Separate cell from one another
3. Provide an abundant surface on which chemical reaction can occur.
4. Regulate the passage of materials in to and out of cells. It also let some things in and keeps others out. The quality selective permeability
Movement across-cell membrane
Movements a cross membrane takes place in two ways.These are passive and active movements. Passive movement uses energy whereas active movement consumes energy in the form of ATP.
Passive movement: includes
a. Simple diffusion, the random movements of molecules from area of high concentration to the area of low concentration. Example air in alveoli of lung
b. Facilitated diffusion, larger molecules, which are not soluble in lipid need protein channel to pass through the plasma membrane. No direct energy needed. Example: -Amino acid passes through the cell membrane.
c. Osmosis, a special type of diffusion referring to the passage of water through a selectively permeable membrane from an area of high water concentration to lower water concentration.
d. Filtration, small molecules pass through selectively permeable membrane in response to force of pressure.Example: - filtration in the kidney in the process of urine formation.
Active movements across membranes
Substances move through a selectively permeable membrane from areas of low concentration on side of a membrane to an area of higher concentration on the other side. This is against concentration gradient. Therefore, it requires energy.
a) Active Transport: till equilibrium substances could more by passive movement. But if equilibrium reached and still more molecules are needed, they must be pumped through the membrane against concentration gradient.This process requires the use of ATP. One example of such processes is Sodium – potassium pump and calcium pump. In this process all follows similar process. These are molecules bind to carrier protein, molecule- carrier complex pass through the membrane, assisted by an enzyme & ATP and carrier protein returns to its original shape & repeat the process.
b) Endocytosis, pocketing in by plasma membrane. It includes:
Pinocytoss – cell drinking Receptor – mediated Endocytosis- Endocytosis with the
help of receptor.Phagocytosis- cell eating.
c) Exocytosis, opposite to Endocytosis, to remove out undigested particles.
Cytoplasm
Cytoplasm is a matrix or ground substance in which various cellular components are found. It is thick semi transparent, elastic fluid containing suspended particles and a series of minute tubules and filaments that form cytoskeleton. Water constitutes 75-90% of the cytoplasm. It also contains solid components, proteins, carbohydrates, lipids and inorganic substances. The inorganic components exist as solutions because they are soluble in water. The majority of organic substances however are found as colloids. Colloids are particles that remain suspended in the surrounding medium.
Organelles
Organelles are specialized portion of the cell with a characteristic shape that assume specific role in growth,maintenance, repair and control.
a) Nucleus, Oval in shape and is the largest structure in the cell. Contain the hereditary factor in the cell. Hence it controls cell activity & structure. Most cell contain single nucleus but some like matured Red Blood cell do not contain. However Muscle cell contain several nucleuses.The nucleus separated from other cell structure by double membrane called nuclear membrane. Pores over the nuclear membrane allow the nucleus to communicate with the cytoplasm. In the nucleus a jelly like fluid that fill the nucleus is karylymph (neucleoplasm), which contain the genetic material called chromosome. Nucleus also contain dark, somewhat spherical, non-membrane bound mass called nucleolus. It contains DNA, RNA and protein,which assist in the construction of ribosome.
b) Ribosome, tiny granules, composed of Ribosomal RNA (rRNA). They are site of protein synthesis.
c) Endoplasmic reticulum is a double membrane channel. It is continuous with the nuclear membrane. It involved in intracellular exchange of material with the cytoplasm.Various products are transported from one portion of the cell to another via the endoplasmic reticulum. So it is considered as intracellular transportation. It is also storage for synthesized molecules. Together with the Golgi complex it serves as synthesis & packaging center.Endoplasmic reticulum (ER) is divided in to two. These are, granular E.R. Containing granule and involving in synthesis of protein and agranular E.R. that synthesize lipid & involves in detoxification.
d) Golgi Complex, near to the nucleus. It consist 4-8 membranous sacs. It process, sort, pack & deliver protein to various parts of the cell.
e) Mitochondria, a small, spherical, rod shaped or filamentous structure. It generates energy. Each mitochondria posses two membrane, one is smooth (upper) membrane and the other is arranged with series of folds called cristae. The central cavity of a mitochondrion enclosed by the inner membrane is the matrix.
f) Lysosomes appear as membrane enclosed spheres. They are formed from Golgi complexes & have single membrane. They contain powerful digestive (hydrolytic enzyme capable of breaking down many kinds of molecules. The lysosomal enzyme believed to be synthesized in the granular endoplasmic reticulum and Golgi complex.
g) The cyto-skeleton, the cytoplasm has a complex internal structure consisting of a series of exceedingly small microfilaments, microtubule & intermediate filaments together referred to as the cyto-skeleton.
h) Centrosme, a dense area of cytoplasm generally spherical and located near the nucleus it contain centrioles. It also contains DNA that controls their replication. Centrosmes are made of microtubules, which seam drinking straws. They are Involved in the movement of chromosome during cell division.
i) Cilia/flagella, thread like appendages, which are made of microtubules. When they are beating forms rhythmic movement. They are found in female reproductive organ
and upper respiratory tube.
Cell inclusion
Large and diverse group of chemicals, which are produced by cells, are cell inclusions. It is mainly organic and includes melanin, glycogen & Lipids.
Cells out of control/cancer
Normal human body cells usually divide at a controlled rate required to replace the dying ones and for growth. Cancer cells are different. They lack the controlling mechanism.Cancer occurs when cells grows and divide at abnormal rate& then spread beyond the original site. Some of the risk factors for cancer occurrence are radiation, chemicals,extreme pressure and hormonal therapy.Click here to access Unit one Content..
Topic Three[Cont'd]
Introduction to cell divison.
· Cell division is the process by which a parent cell divides and gives rise to two or more daughter cells. It is a means of reproduction for single-cell organisms.
· In multicellular organisms, cell division contributes to growth, development, repair, and the generation of reproductive cells (sperms and eggs).
· Cell division is a tightly regulated process, and aberrant cell division can cause diseases, notably cancer.
Significance of cell division.
1. Distributes the identical genetic material to daughter cell.
2. With the cell division growth occur through an increase in volume and enlargement of the outer membrane.
3. Without cell division death will quickly ensure no further propagation of life.
4. Cell division enables sexually reproducing organisms to develop from a single cell i.e. the fertilized egg or zygote.
5. Cell division involves repairing of cells e.g bone marrow makes the new blood cells.
The cell cycle
The cell cycle is made up of two main stages: interphase and mitosis
- During interphase, cells are duplicating their material and synthesizing proteins to prepare to divide.
- Interphase encompasses 3 phases: G1, S and G2. During S phase, DNA is replicated.
- Mitosis encompasses prophase, prometaphase, metaphase, anaphase telophase.
- During the final stages of the cell cycle, cytokinesis occurs, where the cytoplasmic contents are separated into two daughter cells.
- The cell cycle describes a sequence of reactions that results in the growth of the cell and replication of the genetic material to make two identical daughter cells.
- These events are tightly regulated and precisely timed, and can be grouped into two phases: interphase and the mitotic (M) phase.
- During interphase, the cell grows and DNA is replicated, and during the mitotic phase, the cell divides and the DNA is distributed to the daughter cells.
- A typical human cell cycle takes around 24 hours, but the cell cycle can be drastically different in different cell type.
Interphase
Interphase is subdivided into three phases:
· G1,
· S
· G2.
G1 phase.
· The first phase of interphase and the cell cycle is called G1.
· During G1, the cell is preparing to replicate DNA by synthesizing the mRNAs and proteins required to execute the future steps.
· The cell usually grows larger, and some organelles are copied.
S phase.
· During the S phase, all the genetic information in the cell is copied by the process of DNA replication.
· This process of replication generates sister chromatids, which are identical pairs of chromosomes.
· These sister chromatids are attached to each other by a centromere.
· A centromere is a specialized sequence of DNA that links the sister chromatids and is important throughout mitosis.
G2 phase
· The final phase of interphase is the G2 phase.
· During this time, the cell undergoes additional growth, replenishes energy stores and prepares and reorganizes the cytoplasmic components for division, including duplicating some organelles and dismantling the cytoskeleton.
· G2 ends when mitosis begins.
Mitosis (M)
· The mitotic phase describes a series of processes during which the replicated DNA condenses into visible chromosomes, which are aligned, separated, and passed on to two new daughter cells.
· The movement of chromosomes is orchestrated by specialized structures called microtubules.
Prophase
· During prophase, the chromosomes start to condense the nuclear envelope breaks down, and the associated organelles break up and move towards the edge of the cell.
· A structure called the mitotic spindle also starts to form here.
· This structure is made of microtubules and is important in moving chromosomes around during mitosis.
· The mitotic spindles extend from either side of the cell (at opposite poles).
Prometaphase
· Prometaphase is sometimes not classified as an independent step and can be referred to as late prophase.
· During prometaphase, the processes begun in prophase continue: the nuclear envelope is broken down, and the chromosomes are fully condensed.
· The mitotic spindle grows and begins to organize the chromosomes.
· A special structure called the kinetochore appears at this stage.
· The kinetochore is a protein structure is important for linking the chromosomes to the mitotic spindle and is assembled on the centromere.
Metaphase
· During metaphases, the mitotic spindle facilitates the movement of chromosomes such that they align along the Centre of the cell, at the metaphase plate.
· At this point, sister chromatids are still attached to one another. Following metaphase, there is an important checkpoint called the spindle checkpoint.
· This ensures anaphase will not proceed unless all the chromosomes are at the metaphase plate and attached to microtubules (by the kinetochore).
· This is a hugely important checkpoint ensuring that each daughter cell receives the correct number of chromosomes.
Anaphase
· When the chromosomes are properly aligned, anaphase can proceed.
· Anaphase is the process during which the sister chromatids separate at the centromere and are pulled to the edge of the cell.
· These chromatids are now referred to as chromosomes.
Telophase
· During telophase, the spindle disappears and a new the nuclear envelope forms around the chromosomes.
· The chromosomes also start to decondense as cytokinesis is taking place.
Cytokinesis
· Cytokinesis completes the cell cycle, and usually overlaps with the final stages of mitosis.
· Cytokinesis involves in the physical separation of the cytoplasm and its components into daughter cells.
· This occurs when a ring of cytoskeletal fibres (called the contractile ring) form at the centre of the cell, making an indentation called the cleavage furrow.
· This ring tightens, eventually pinching the cell enough that it separates it to give two new daughter cells.
· Cytokinesis is more complex in plant cells, which have a cell wall. Dividing plant cells overcome this by creating a structure called the cell plate, which is made from vesicles containing plasma membrane and cell wall components.
· The cell plate enlarges until it merges with the cell walls. This divides the cell in two and allows the cell wall to be regenerated.
G0 phase and cell cycle exit
· Not all cells are actively dividing. A cell in the G0 phase nbsp;is said to be in a resting phase, and these cells are also called quiescent.
· This means it is not dividing or preparing to divide. Cells can enter G0 temporarily until there is a signal to divide, or can remain in G0 indefinitely.
· Examples of cells in G0 include neurons, which are metabolically active but not dividing.
Cell cycle regulation
· At several points in the mitotic cell cycle, a checkpoint operates.
· These checkpoints regulate the progression of the cycle, ensuring mistakes are not passed on to the daughter cells.
· These key checkpoints occur at the end of G1, between G2/M and during metaphase.
· Cell cycle checkpoints are regulated by cell-signalling proteins.
· At the G1 checkpoint, two features are checked: whether the conditions are appropriate for proceeding with the cell cycle, and DNA damage.
· The cell will only pass the checkpoint when it is large enough and has enough energy, and also that the external conditions are favorable for division.
· The cell also checks for DNA damage, and the cycle will not proceed if damaged DNA is detected, as there would be negative consequences if the daughter cells inherited damaged genetic material.
· G1 also contains a special checkpoint called the restriction point, the point at which the cell irreversibly commits to entering the cycle.
· At the G2/M checkpoint, the cell ensures the chromosomes have been replicated correctly.
The metaphase checkpoint, also known as the spindle checkpoint, ensures that the cell cycle will not proceed until all the sister chromatids are properly attached to the mitotic spindle.Click here to access Unit Two Content..
Topic 1: Continuation
The Skin
Skin is the largest organ in the body occupying almost 2m2 of surface area thickens of 2mm. Skin has 3 main parts. These are the epidermis, dermis and hypodermis.
Epidermis is the outer layer of the skin that is made of stratified squamous epithelium. It has no blood supply.Epidermis contains 4-5 strata. These are stratum cornium,lucidium, granulosum,spinosum and basale,
Stratum cornium is the outer, dead, flat, Keratinized and thicker layer.Stratum lucidium is next to stratum cornium. It consists of flat,translucent layers of cells. This stratum is found in thick skin only.
Stratum granulosum lies just below stratum lucidium. The cells in this layer are in the process of keratinization.
Stratum spinosum: next down to stratum granulosum. The cells in this stratum have a polyhydral shape and they are in the process of protein synthesis.
Stratum basale rests on the basement membrane, and it is the last layer of epidermis next to stratum spinosum. Stratum basale together with stratum spinosum constitute stratum
germinativum.
Dermis / true skin/ a strong, flexible, connective tissue meshwork of collagen, reticular and elastic fibers. Most part of the skin is composed of dermis.
Dermis contains papillary and reticular layers. Papillary layer is next to stratum basale of the epidermis. It contains loose connective tissue with in the bundles of collagenous fibers. It also contains loose capillaries that nourish the epidermis. In some areas papillary layer have special nerve endings that serve as touch receptors (meissner’s corpuscles).
Indentations of papillary layer in the palms and soles reflected over the epidermis to create ridges.
Reticular layer: next to papillary layer. It is made of dense connective tissue with course of collagenous fiber bundles that crisscross to form a storma of elastic network. In the reticular layer many blood and lymphatic vessels, nerves, fat cell, sebaceous (oil) glands and hair roots are embedded.
Receptors of deep pressure (pacinian corpuscles) are distributed through out the dermis.
Hypoderms: it is found beneath the dermis. It is a subcutaneous layer (under the skin). Hypodermis is composed of loose, fibrous connective tissue, which is richly supplied with lymphatic and blood vessels and nerves.Hypodermis is much thicker than dermis. With in it coils of ducts of sudoriferous (sweat) glands, and the base of hair follicles.
Functions of Skin
1. Protection: against harmful microorganisms, foreign material and it prevents excessive loss of body fluid.
2. Temperature regulation: with the sweat, heat leaves the body
3. Excretion: Small amount of waste products from the body such as urea
4. Synthesis: By the action of UV. Vitamin D is synthesized in the skin. Vitamin D is necessary for absorption calcium from intestine.
5. Sensory reception: it contains sensory receptors of heat,cold, touch, pressure, and pain.
4.1.2 Color of the skin
Skin’s color is determined by 3 factors
1. The presence of melanin a dark pigment produced by specialized cell called melanocyte
2. The accumulation of yellow pigment carotene.
3. The color of blood reflected through the epidermis
* The main function of melanin is to screen out excessive ultraviolet rays.
* All races have some melanin in their skins although the darker races have slightly more melanocyte. The person who is genetically unable to produce any melanin is an albino.
Glands of the Skin
Glands of the skin are the sudoriferous and sebaceous glands.
Sudoriferous /sweat/ glands
Types: Eccrine and Apocrine glands
Eccrine glands are small, simple coiled tubular glands distributed over nearly the entire body, and they are absent over nail beds, margins of lips of vulva, tips of penis. Eccrine glands are numerous over the palms and soles. Their secretary portion is embedded in the hypodermis. The sweat they secret is colorless, aqueous fluid containing neutral fats,albumin, urea, lactic acid and sodium chloride. Its excretion helps body temperature to be regulated.
Apocrine glands are odiferous, found at the armpits, in the dark region around nipples, the outer lips of the vulva, and the anal and genital regions. They are larger and deeply situate than eccrine sweet glands. An apocrine sweet gland becomes active at puberty. They respond to stress including sexual activity. The female breasts are apocrine glands that have become adapted to secret and release milk instead of sweat. The ceruminous glands in the outer ear canal are also
apocrine skin glands.
Sebaceous (Oil) glands
Sebaceous glands are simple branched alveolar glands found in the dermis. Their main functions are lubrication and protection. They are connected to hair follicles and secret oily secretion called sebum. It is a semi fluid substance composed of entirely lipids. It functions as a permeability barrier, an emollient (skin softening) and a protective a gent against bacteria and fungi. This type of gland found all over the body except in the palms and soles. Acne vulgaris is a condition when there is over secretion of sebum, which may enlarge the gland and plug the pore.
Hair
Hair is composed of Keratinized threads of cells, which develops from the epidermis. Because it arises from the skin,it is considered an appendage of the skin. It covers the entire body except the palms, soles, lips, tip of penis, inner lips of vulva and nipples.
Function
1. Insulation against cold in scalp
2. Against glare in eye brows
3. Screen against foreign particles (eye lashes)
4. In the nostrils trap dust particles in the inhaled air
5. Protect openings from foreign particles.
Structure of Hair
Hair has two parts, the shaft the part above skin and the root embedded in the skin. Hair consist epithelial cell arranged in three layers from the inside out medulla, cortex and cuticle.
The lower portion of the root, located in the hypodermis enlarges to form the bulbs. The bulb is composed of the matrix of epithelial cells. The bulb pushes in ward along its bottom to form a papilla of blood rich connective tissue. Part of the hair follicle is attached with the bundle of smooth muscle about halfway down the follicle. These are arrecter pili muscles. When it contracts in pulls the follicles and its hair to an erect position producing goose bump. Hair grows and when it finishes its growth sheds. The growth rate of hair depends on its position. The fastest growth rate occurs over the scalp of women aged 16 to 24 years. Scalp hair grows 0.4
m.m per day (an average scalp contain 125.000 hairs). Hair sheds when it growth is complete. Just before a hair is to be shed, the matrix cell gradually become inactive and
eventually dies.
Nail
The structure and function of human nails .
1. The Nail Bed: This is the portion of skin upon which the nail plate rests. It has very rich supply of blood and lymph vessels to keep nail healthy. The function of the nail bed is to supply nourishment and protection.
2. Nail Plate: The nail plate is composed of layers of keratinized skin cells. The layers are packed very closely together with fat but very little water content. The nail gradually grows over the nail bed and becomes free edge. There are no blood vessels or nerves in the nail plate. The pink color of the nail plate derives from the blood vessels that passes beneath it. The main function of the nail plate is to protect the living nail bed of the fingers and toes.
3. The Free Edge: The nail plate leaves the end of the finger and forms a projection that is called the free edge. This is attached to the nail bed and appears as white. The function of the free edge is to protect the fingertip and the hyponychium. This is the part we file and shape!
4. The Hyponychium: This is a part of the epidermis under the free edge of the nail plate. Its function is to protect the nail bed from infection.
5. The Nail Grooves: This lies alongside of the edge of the nail plate. The function of the nail groove is to keep the nail growing in a straight line.
6. The Matrix: This is the growing area of the nail and sometimes called as the nail root. The shape and size of the matrix determines the thickness of the nail. The process of the keratinization takes place in the epidermal cells of the matrix, forming the hardened tissue of the nail plate. The function of the matrix is to produce new nail cells.
7. The Nail Mantle: The nail mantle is the layer of epidermis at the base of the nail, before the cuticle. The function of the nail mantle is to protect the matrix from physical damage.
8. The Lunula: This is located at the base of the nail, lying over the matrix. It is white in color and known as half-moon. The nail is slightly soft in this area and can be easily damaged.
9. The Cuticle: The overlapping epidermis around the base of the nail is called the cuticle. The function of the cuticle is to protect the matrix from infection.
10. The Nail Walls: These are the folds of the skin overlapping the sides of the nails. The function of the nail wall is to protect the nail plate edges.
11. The Perionychium: This is the collective name given to the nail walls and the cuticle area.
12. The Eponychium: This is the extension of the cuticle at the base of the nail plate, under which the nail plate emerges from matrix. The function of eponychium is to protect matrix from infection.
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Topic 1: Continuation
Functions of the skeleletal system.
1. Support: it forms the internal framework that supports and anchors all soft organs.
2. Protection: bones protect soft body organs.
3. Movement: skeletal muscles attached to the skeletal system use the bone to levers to move the body and its part.
4. Storage: fat is stored in the internal cavities of bones. Bone it self-serves as a storehouse of minerals. The most important being calcium and phosphors.
5. Blood cell formation: it occurs within the marrow cavities of certain bones.
Bone tissue.
The bone tissue consists of the following.
1. Osteocytes (cells) are found in the matrix of calcium phosphate, calcium carbonate, and collagen.
2. Compact bone—haversian systems are present.
3. Spongy bone—no haversian systems; red bone marrow present.Articular cartilage—smooth, on joint surfaces.
4. Periosteum—fibrous connective tissue membrane;anchors tendons and ligaments; has blood vessels that enter the bone.
Classification of Bones
1. Long—arms, legs; shaft is the diaphysis (compact bone) with a marrow cavity containing yellow bone marrow (fat); ends are epiphyses (spongy bone)
2. Short—wrists, ankles (spongy bone covered with compact bone).
3. Flat—ribs, pelvic bone, cranial bones (spongy bone covered with compact bone).
4. Irregular—vertebrae, facial bones (spongy bone covered with compact bone).
Embryonic Growth of Bone
1. The embryonic skeleton is first made of other tissues that are gradually replaced by bone. Ossification begins in the third month of gestation; osteoblasts differentiate from fibroblasts and produce bone matrix.
2. Cranial and facial bones are first made of fibrous connective tissue; osteoblasts produce bone matrix in a center of ossification in each bone; bone growth radiates outward; fontanels remain at birth, permit compression of infant skull during birth; fontanels are calcified by age 2 .
3. All other bones are first made of cartilage; in a long bone the first center of ossification is in the diaphysis,other centers develop in the epiphyses. After birth a long bone grows at the epiphyseal discs:
4. Cartilage is produced on the epiphysis side, and bone replaces cartilage on the diaphysis side.
5. Osteoclasts form the marrow cavity by reabsorbing bone matrix in the center of the diaphysis
Tha anatomical structure of a bone.
long bone shows the gross anatomical characteristics of bone. The wider section at each end of the bone is called the epiphysis (plural = epiphyses), which is filled with spongy bone. Red marrow fills the spaces in the spongy bone. Each epiphysis meets the diaphysis at the metaphysis, the narrow area that contains the epiphyseal plate (growth plate), a layer of hyaline (transparent) cartilage in a growing bone. When the bone stops growing in early adulthood (approximately 18–21 years), the cartilage is replaced by osseous tissue and the epiphyseal plate becomes an epiphyseal line.
The medullary cavity has a delicate membranous lining called the endosteum (end- = “inside”; oste- = “bone”), where bone growth, repair, and remodeling occur. The outer surface of the bone is covered with a fibrous membrane called the periosteum (peri– = “around” or “surrounding”). The periosteum contains blood vessels, nerves, and lymphatic vessels that nourish compact bone. Tendons and ligaments also attach to bones at the periosteum. The periosteum covers the entire outer surface except where the epiphyses meet other bones to form joints). In this region, the epiphyses are covered with articular cartilage, a thin layer of cartilage that reduces friction and acts as a shock absorber.
Periosteum and Endosteum. The periosteum forms the outer surface of bone, and the endosteum lines the medullary cavity.
Flat bones, like those of the cranium, consist of a layer of diploë (spongy bone), lined on either side by a layer of compact bone. The two layers of compact bone and the interior spongy bone work together to protect the internal organs. If the outer layer of a cranial bone fractures, the brain is still protected by the intact inner layer.
Factors That Affect Bone Growth and Maintenance
1. Heredity—many pairs of genes contribute to genetic potential for height.
2. Nutrition—calcium, phosphorus, and protein become part of the bone matrix; vitamin D is needed for absorption of calcium in the small intestine;vitamins C and A are needed for bone matrix production (calcification).
3. Hormones—produced by endocrine glands; concerned with cell division, protein synthesis, calcium metabolism, and energy production
4. Exercise or stress—weight-bearing bones must bear weight or they will lose calcium and become brittle.
Functions of bones.
- Supports the body
- Facilitates movement
- Protects internal organs
- Produces blood cells
- Stores and releases minerals and fat
The Skeleton—206 bones are connected by ligaments
1. Axial—skull, vertebrae, rib cage.
• Skull
• Eight cranial bones form the braincase, which also protects the eyes and ears; 14 facial bones make up the face; the immovable joints between these bones are called sutures.
• Paranasal sinuses are air cavities in the maxillae,frontal, sphenoid, and ethmoid bones; they
lighten the skull and provide resonance for voice.
• Three auditory bones in each middle ear cavity transmit vibrations for the hearing process.
• Vertebral column.
• Individual bones are called vertebrae: 7 cervical,12 thoracic, 5 lumbar, 5 sacral (fused into one sacrum), 4 to 5 coccygeal (fused into one coccyx). Supports trunk and head, encloses and protects the spinal cord in the vertebral canal. Discs of fibrous cartilage absorb shock between the bodies of adjacent vertebrae, also permit slight movement. Four natural curves center head over body for walking upright (see
• Rib cage
• Sternum and 12 pairs of ribs; protects thoracic and upper abdominal organs from mechanical injury and is expanded to contribute to inhalation.Sternum consists of manubrium, body,and xiphoid process. All ribs articulate with thoracic vertebrae; true ribs (first seven pairs) articulate directly with sternum by means of costal cartilages; false ribs (next three pairs) articulate with 7th costal cartilage; floating ribs (last two pairs) do not articulate with the sternum.
2. Appendicular—bones of the arms and legs and the shoulder and pelvic girdles.
• Shoulder and arm
• Scapula—shoulder muscles are attached; glenoid fossa articulates with humerus.
• Clavicle—braces the scapula.
• Humerus—upper arm; articulates with the scapula and the ulna (elbow).
• Radius and ulna—forearm—articulate with one another and with carpals.
• Carpals—eight—wrist; metacarpals—five—hand; phalanges—14—fingers (for joints, see
• Hip and leg
• Pelvic bone—two hip bones; ilium, ischium, pubis; acetabulum articulates with femur.
• Femur—thigh; articulates with pelvic bone
and tibia (knee).
• Patella—kneecap; in tendon of quadriceps femoris muscle.
• Tibia and fibula—lower leg; tibia bears weight;fibula does not bear weight, but does anchor muscles and stabilizes ankle.
• Tarsals—seven—ankle; calcaneus is heel bone.
• Metatarsals—five—foot; phalanges—14—toes
Joints—Articulations
1. Classification based on amount of movement:
• Synarthrosis—immovable.
• Amphiarthrosis—slightly movable.
• Diarthrosis—freely movable
2. Synovial joints—all diarthroses have similar structure
• Articular cartilage—smooth on joint surfaces.
• Joint capsule—strong fibrous connective tissue sheath that encloses the joint.
• Synovial membrane—lines the joint capsule;secretes synovial fluid that prevents friction.
• Bursae—sacs of synovial fluid that permit tendons to slide easily across joints.
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Topic 1: Continuation
Functions of the Nervous System
1. Detect changes and feel sensations.
2. Initiate responses to changes.
3. Organize and store information.
Divisions of the Nervous System
1. Central nervous system (CNS)—brain and spinal cord.
2. Peripheral nervous system (PNS)—cranial nerves and spinal nerves.
Nerve Tissue—neurons (nerve fibers) and specialized cells (Schwann, neuroglia)
1. Neuron cell body contains the nucleus; cell bodies are in the CNS or in the trunk and are protected by bone.
2. Axon carries impulses away from the cell body;dendrites carry impulses toward the cell body.
3. Schwann cells in PNS: Layers of cell membrane form the myelin sheath to electrically insulate neurons;nodes of Ranvier are spaces between adjacent Schwann cells. Nuclei and cytoplasm of Schwann cells form the neurolemma, which is essential for regeneration of damaged axons or dendrites
4. Oligodendrocytes in CNS form the myelin sheaths; microglia phagocytize pathogens and damaged cells; astrocytes contribute to the blood–brain barrier
5. Synapse—the space between the axon of one neuron and the dendrites or cell body of the next neuron.A neurotransmitter carries the impulse across a synapse and is then destroyed by a chemical inactivator.Synapses make impulse transmission one way in the living person.
Types of Neurons—nerve fibers
1. Sensory—carry impulses from receptors to the CNS; may be somatic (from skin, skeletal muscles,joints) or visceral (from internal organs).
2. Motor—carry impulses from the CNS to effectors;may be somatic (to skeletal muscle) or visceral (to smooth muscle, cardiac muscle, or glands). Visceral motor neurons make up the autonomic nervous system.
3. Interneurons—entirely within the CNS.
Nerves and Nerve Tracts
1. Sensory nerve—made only of sensory neurons.
2. Motor nerve—made only of motor neurons.
3. Mixed nerve—made of both sensory and motor neurons.
4. Nerve tract—a nerve within the CNS; also called white matter.
The Nerve Impulse
1. Polarization—neuron membrane has a (_+) charge outside and a (_-_) charge inside.
2. Depolarization—entry of Sodium ions and reversal of charges on either side of the membrane.
3. Impulse transmission is rapid, often several meters per second.
4. Saltatory conduction—in a myelinated neuron only the nodes of Ranvier depolarize; increases speed of impulses.
The Spinal Cord
1. Functions: transmits impulses to and from the brain, and integrates the spinal cord reflexes.
2. Location: within the vertebral canal; extends from the foramen magnum to the disc between the 1st and 2nd lumbar vertebrae.
3. Cross-section: internal H-shaped gray matter contains cell bodies of motor neurons and interneurons; external white matter is the myelinated axons and dendrites of interneurons.
4. Ascending tracts carry sensory impulses to the brain; descending tracts carry motor impulses away from the brain.
5. Central canal contains cerebrospinal fluid and is continuous with the ventricles of the brain.
Spinal Nerves for major peripheral nerves
1. Eight cervical pairs to head, neck, shoulder, arm,and diaphragm; 12 thoracic pairs to trunk; 5 lumbar pairs and 5 sacral pairs to hip, pelvic cavity, and leg; 1 very small coccygeal pair.
2. Cauda equina—the lumbar and sacral nerves that extend below the end of the spinal cord.
3. Each spinal nerve has two roots: dorsal or sensory root; dorsal root ganglion contains cell bodies ofsensory neurons; ventral or motor root; the two roots unite to form a mixed spinal nerve.
Spinal Cord Reflexes—do not depend directly on the brain
1. A reflex is an involuntary response to a stimulus.
2. Reflex arc—the pathway of nerve impulses during a reflex: (1) receptors, (2) sensory neurons, (3) CNS with one or more synapses, (4) motor neurons,(5) effector that responds.
3. Stretch reflex—a muscle that is stretched will contract; these reflexes help keep us upright against gravity. The patellar reflex is also used clinically to assess neurologic functioning, as are many other reflexes.
4. Flexor reflex—a painful stimulus will cause withdrawal of the body part; these reflexes are protective.
The Brain—many parts that function as an integrated whole
1. Ventricles—four cavities: two lateral, 3rd, 4th; each contains a choroid plexus that forms cerebrospinal fluid .
2. Medulla—regulates the vital functions of heart rate, breathing, and blood pressure; regulates reflexes of coughing, sneezing, swallowing, and vomiting.
3. Pons—contains respiratory centers that work with those in the medulla.
4. Midbrain—contains centers for visual reflexes,auditory reflexes, and righting (equilibrium) reflexes.
5. Cerebellum—regulates coordination of voluntary movement, muscle tone, stopping movements, and equilibrium; contributes to sensations involving texture and weight.
6. Hypothalamus—produces antidiuretic hormone (ADH), which increases water reabsorption by the kidneys; produces oxytocin, which promotes uterine contractions for labor and delivery; produces releasing hormones that regulate the secretions of the anterior pituitary gland; regulates body temperature; regulates food intake; integrates the functioning of the autonomic nervous system (ANS);promotes visceral responses to emotional situations; acts as a biological clock that regulates body rhythms.
7. Thalamus—groups sensory impulses as to body part before relaying them to the cerebrum; awareness of pain but inability to localize; suppresses unimportant sensations to permit concentration; contributes to alertness and awareness, and to memory.
8. Cerebrum—two hemispheres connected by the corpus callosum, which permits communication between the hemispheres. The cerebral cortex is the surface gray matter, which consists of cell bodies of neurons and is folded extensively into convolutions.
9. The internal white matter consists of nerve tracts that connect the lobes of the cerebrum to one another and to other parts of the brain.
· Frontal lobes—motor areas initiate voluntary movement; premotor area regulates sequences of movements for learned skills; prefrontal area for aspects of social behavior; Broca’s motor speech area (left hemisphere) regulates the movements involved in speech.
· Parietal lobes—general sensory area feels and interprets the cutaneous senses and conscious muscle sense; taste area extends into temporal lobe, for sense of taste; speech areas (left hemisphere) for thought before speech.
· Temporal lobes—auditory areas for hearing and interpretation; olfactory areas for sense of smell and interpretation; speech areas for thought before speech.
· Occipital lobes—visual areas for vision; interpretation areas for spatial relationships.
· Association areas—in all lobes, for abstract thinking, reasoning, learning, memory, and personality. The hippocampi are essential for the formation of memories. Neural plasticity is the ability of the brain to adapt to changing needs.
· Basal ganglia—gray matter within the cerebral hemispheres; regulate accessory movements and muscle tone.
Meninges and Cerebrospinal Fluid (CSF)
1. Three meningeal layers made of connective tissue:outer—dura mater; middle—arachnoid membrane;inner—pia mater; all three enclose the brain and spinal cord.
2. Subarachnoid space contains CSF, the tissue fluid of the CNS.
3. CSF is formed continuously in the ventricles of the brain by choroid plexuses, from blood plasma.
4. CSF circulates from the ventricles to the central canal of the spinal cord and to the cranial and spinal subarachnoid spaces.
5. CSF is reabsorbed from the cranial subarachnoid space through arachnoid villi into the blood in the cranial venous sinuses. The rate of reabsorption equals the rate of production.
6. As tissue fluid, CSF brings nutrients to CNS neurons and removes waste products. CSF also acts as a shock absorber to cushion the CNS.
Cranial Nerves—12 pairs of nerves that emerge from the brain
They are concerned with vision, hearing and equilibrium, taste and smell, and many other functions.
The Autonomic Nervous System (ANS)
1. Has two divisions: sympathetic and parasympathetic;their functioning is integrated by the hypothalamus.
2. Consists of motor neurons to visceral effectors:smooth muscle, cardiac muscle, and glands.
3. An ANS pathway consists of two neurons that synapse in a ganglion:
· Preganglionic neurons—from the CNS to the ganglia
· Postganglionic neurons—from the ganglia to the effectors
· Most sympathetic ganglia are in two chains just outside the vertebral column; parasympathetic ganglia are very near or in the visceral effectors.
4. Neurotransmitters: acetylcholine is released by all preganglionic neurons and by parasympathetic postganglionic neurons; the inactivator is cholinesterase. Norepinephrine is released by most sympathetic postganglionic neurons; the inactivator is COMT or MAO.
5. Sympathetic division—dominates during stress situations; responses prepare the body to meet physical demands.
6. Parasympathetic division—dominates in relaxedsituations to permit normal
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Topic 1: Continuation
Organ Systems Involved in Movement
1. Muscular—moves the bones.
2. Skeletal—bones are moved, at their joints, by muscles.
3. Nervous—transmits impulses to muscles to cause contraction.
4. Respiratory—exchanges O2 and CO2 between the air and blood.
5. Circulatory—transports O2 to muscles and removes CO2.
Muscle Structure
1. Muscle fibers (cells) are specialized to contract,shorten, and produce movement.
2. A skeletal muscle is made of thousands of muscle fibers. Varying movements require contraction of variable numbers of muscle fibers in a muscle.
3. Tendons attach muscles to bone; the origin is the more stationary bone, the insertion is the more
movable bone. A tendon merges with the fascia of a muscle and the periosteum of a bone; all are made of fibrous connective tissue.
Muscle Arrangements
1. Antagonistic muscles have opposite functions. A muscle pulls when it contracts, but exerts no force when it relaxes and it cannot push. When one muscle pulls a bone in one direction, another muscle is needed to pull the bone in the other direction .
2. Synergistic muscles have the same function and alternate as the prime mover depending on the
position of the bone to be moved. Synergists also stabilize a joint to make a more precise movement possible
3. The frontal lobes of the cerebrum generate the impulses necessary for contraction of skeletal muscles.The cerebellum regulates coordination.
Muscle Tone—the state of slight contraction present in muscles
1. Alternate fibers contract to prevent muscle fatigue;regulated by the cerebellum.
2. Good tone helps maintain posture, produces 25% of body heat (at rest), and improves coordination.
3. Isotonic exercise involves contraction with movement;improves tone and strength and improves cardiovascular and respiratory efficiency (aerobic exercise).
· Concentric contraction—muscle exerts force while shortening.
· Eccentric contraction—muscle exerts force while lengthening.
4. Isometric exercise involves contraction without movement; improves tone and strength but is not aerobic.
Muscle Sense—proprioception: knowing where our muscles are without looking at them
1. Permits us to perform everyday activities without having to concentrate on muscle position.
2. Stretch receptors (proprioceptors) in muscles respond to stretching and generate impulses that
5. the brain interprets as a mental “picture” of where the muscles are. Parietal lobes: conscious muscle sense; cerebellum: unconscious muscle sense used to promote coordination.
Energy Sources for Muscle Contraction
1. ATP is the direct source; the ATP stored in muscles lasts only a few seconds.
2. Creatine phosphate is a secondary energy source; isbroken down to creatine _ phosphate _ energy.The energy is used to synthesize more ATP. Some creatine is converted to creatinine, which must be excreted by the kidneys. Most creatine is used for the resynthesis of creatine phosphate.
3. Glycogen is the most abundant energy source and is first broken down to glucose. Glucose is broken down in cell respiration:ATP is used for contraction; heat contributes to body temperature; H2O becomes part of intracellular fluid; CO2 is eventually exhaled.
4. Oxygen is essential for the completion of cell respiration.Hemoglobin in red blood cells carries oxygen to muscles; myoglobin stores oxygen in muscles; both of these proteins contain iron, which enables them to bond to oxygen.
5. Oxygen debt (recovery oxygen uptake): Muscle fibers run out of oxygen during strenuous exercise, and glucose is converted to lactic acid, which causes fatigue. Breathing rate remains high after exercise to deliver more oxygen to the liver, which converts lactic acid to pyruvic acid, a simple carbohydrate (ATP required).
The structure of a Muscle Fiber
1. Neuromuscular junction: axon terminal and sarcolemma; the synapse is the space between. The axon terminal contains acetylcholine (a neurotransmitter),and the sarcolemma contains cholinesterase (an inactivator) .
2. Sarcomeres are the contracting units of a muscle fiber. Myosin and actin filaments are the contracting proteins of sarcomeres. Troponin and tropomyosin are proteins that inhibit the sliding of myosin and actin when the muscle fiber is relaxed.
3. The sarcoplasmic reticulum surrounds the sarcomeres and is a reservoir for calcium ions.
4. Polarization (resting potential): When the muscle fiber is relaxed, the sarcolemma has a positive charge outside and a negative charge inside. Sodium ions are more abundant outside the cell and Potassium ions are more abundant inside the cell. The Sodium and Potassium pumps maintain these relative concentrations on either side of the cell.
5. Depolarization: This process is started by a nerve impulse. Acetylcholine released by the axon terminal makes the sarcolemma very permeable to Sodium ions, which enter the cell and cause a reversal of charges to Positive charge outside and negative charge inside. The depolarization spreads along the entire sarcolemma and initiates the contraction process.
Contraction—the sliding filament mechanism
1. Depolarization stimulates a sequence of events that enables myosin filaments to pull the actin filaments to the center of the sarcomere, which shortens.
2. All of the sarcomeres in a muscle fiber contract in response to a nerve impulse; the entire cell contracts.
3. Tetanus is a sustained contraction brought about by continuous nerve impulses; all our movements involve tetanus.
4. Paralysis: Muscles that do not receive nerve impulses are unable to contract and will atrophy. Paralysis may be the result of nerve damage, spinal cord damage, or brain damage.
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Topic 1: Continuation
The Chemistry of Hormones
1. Amines—structural variations of the amino acid tyrosine; thyroxine, epinephrine.
2. Proteins—chains of amino acids; peptides are short chains. Insulin, GH, glucagon are proteins; ADH and oxytocin are peptides.
3. Steroids—made from cholesterol; cortisol, aldosterone, estrogen, testosterone.
Regulation of Hormone Secretion
1. Hormones are secreted when there is a need for their effects. Each hormone has a specific stimulus for secretion.
2. The secretion of most hormones is regulated by negative feedback mechanisms: As the hormones exerts its effects, the stimulus for secretion is reversed, and secretion of the hormone decreases.
Pituitary Gland (Hypophysis)
1. Posterior Pituitary (Neurohypophysis)—stores hormones produced by the hypothalamus.These hormones include :
· ADH—increases water reabsorption by the kidneys,decreases sweating, in large amounts causes vasoconstriction. Result: decreases urinary output and increases blood volume; increases BP.Stimulus: nerve impulses from hypothalamus when body water decreases.
· Oxytocin—stimulates contraction of myometrium of uterus during labor and release of milk from mammary glands. Stimulus: nerve impulses from hypothalamus as cervix is stretched or as infant sucks on nipple.
2. Anterior Pituitary (Adenohypophysis)—secretions are regulated by releasing hormones from the hypothalamus
• GH—through intermediary molecules, IGFs,GH increases amino acid transport into cells and increases protein synthesis; increases rate of mitosis; increases use of fats for energy Stimulus: GHRH from the hypothalamus.
• TSH—increases secretion of thyroxine and T3 by the thyroid. Stimulus: TRH from the hypothalamus.
• ACTH—increases secretion of cortisol by the adrenal cortex. Stimulus: CRH from the hypothalamus.
• Prolactin—initiates and maintains milk production by the mammary glands. Stimulus: PRH from the hypothalamus.
• FSH—In women: initiates development of ova in ovarian follicles and secretion of estrogen by follicle cells.In men: initiates sperm development in the testes. Stimulus: GnRH from the hypothalamus.
• LH—In women: stimulates ovulation, transforms mature follicle into corpus luteum and stimulates secretion of progesterone.In men: stimulates secretion of testosterone by the testes. Stimulus: GnRH from the hypothalamus.
Thyroid Gland—on front and sides of trachea
1. Thyroxine (T4) and T3— produced by thyroid follicles. Increase use of all food types for energy and increase protein synthesis. Necessary for normal physical, mental, and sexual development .Stimulus: TSH from the anterior pituitary.
2. Calcitonin—produced by parafollicular cells. Decreases reabsorption of calcium from bones and lowers blood calcium level. Stimulus: hypercalcemia.
Parathyroid Glands
Parathyroid Glands increases reabsorption of calcium and phosphate from bones to the blood; increases
absorption of calcium and phosphate by the small intestine; increases reabsorption of calcium
and excretion of phosphate by the kidneys, and activates vitamin D. Result: raises blood calcium
and lowers blood phosphate levels. Stimulus:hypocalcemia. Inhibitor: hypercalcemia.
Pancreatic hormones
1. Glucagon—secreted by alpha cells. Stimulates liver to change glycogen to glucose; increases use of fats and amino acids for energy. Result: raises blood glucose level. Stimulus: hypoglycemia.
2. Insulin—secreted by beta cells. Increases use of glucose by cells to produce energy; stimulates liver and muscles to change glucose to glycogen;increases cellular intake of fatty acids and amino acids to use for synthesis of lipids and proteins.Result: lowers blood glucose level. Stimulus: hyperglycemia.
3. Somatostatin—inhibits secretion of insulin and glucagon.
Adrenal Glands—
1. Adrenal Medulla—produces catecholamines in stress situations
• Norepinephrine—stimulates vasoconstriction and raises blood pressure.
• Epinephrine—increases heart rate and force,causes vasoconstriction in skin and viscera and vasodilation in skeletal muscles; dilates bronchioles;slows peristalsis; causes liver to change glycogen to glucose; increases use of fats for energy; increases rate of cell respiration. Stimulus: sympathetic impulses from the hypothalamus.
2. Adrenal Cortex—produces mineralocorticoids,glucocorticoids, and very small amounts of sex hormones(function not known with certainty)
• Aldosterone increases reabsorption of sodium and excretion of potassium by the kidneys. Results: hydrogen ions are excreted in exchange for sodium; chloride and bicarbonate ions and water follow sodium back to the blood; maintains normal blood pH, blood volume,and blood pressure. Stimulus: decreased blood sodium or elevated blood potassium;decreased blood volume or blood pressure (activates the renin-angiotensin mechanism of the kidneys).
• Cortisol increases use of fats and amino acids for energy; decreases use of glucose to conserve glucose for the brain; anti-inflammatory effect: blocks effects of histamine and stabilizes lysosomes to prevent excessive tissue damage. Stimulus: ACTH from hypothalamusduring physiological stress.
Ovaries
1. Estrogen—produced by follicle cells. Promotes maturation of ovum; stimulates growth of blood vessels in endometrium; stimulates development of secondary sex characteristics: growth of duct system of mammary glands, growth of uterus, fat deposition. Promotes closure of epiphyses of long bones; lowers blood levels of cholesterol and triglycerides. Stimulus: FSH from anterior pituitary.
2. Progesterone—produced by the corpus luteum.Promotes storage of glycogen and further growth of blood vessels in the endometrium;promotes growth of secretory cells of mammary glands. Stimulus: LH from anterior pituitary.
3. Inhibin—inhibits secretion of FSH.
Testes
1. Testosterone—produced by interstitial cells.Promotes maturation of sperm in testes; stimulates development of secondary sex characteristics:growth of reproductive organs, facial and body hair, larynx, skeletal muscles; promotes closure of epiphyses of long bones. Stimulus: LH from anterior pituitary.
2. Inhibin—produced by sustentacular cells. Inhibits secretion of FSH to maintain a constant rate of sperm production. Stimulus: increased testosterone.
Other Hormones
1. Melatonin—secreted by the pineal gland during darkness; brings on sleep.
2. Prostaglandins—synthesized by cells from the phospholipids of their cell membranes; exert their effects locally. Are involved in inflammation and pain, reproduction, nutrient metabolism, changes in blood vessels, blood clotting.
Mechanisms of Hormone Action
1. A hormone affects cells that have receptors for it. Receptors are proteins that may be part of the cell membrane, or within the cytoplasm or nucleus of the target cell.
2. The two-messenger mechanism: a protein hormone (1st messenger) bonds to a membrane receptor; stimulates formation of cyclic AMP (2nd messenger), which activates the cell’s enzymes to bring about the cell’s characteristic response to the hormone.
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Topic 1: Continuation
Introduction to reproductive system
The reproductive Systems main purpose is to produce gametes (egg and sperm), to ensure
fertilization, and in women to provide a site for the embryo-fetus
Meiosis—the cell division process that produces gametes
1. One cell with the diploid number of chromosomes (46) divides twice to form four cells, each with the haploid number of chromosomes (23).
2. Spermatogenesis takes place in the testes; a continuous process from puberty throughout life; each primary spermatocyte produces four functional sperm . FSH and testosterone are directly necessary.
3. Oogenesis takes place in the ovaries; the process is cyclical (every 28 days) from puberty until menopause; each primary oocyte produces one functional ovum and three non-functional polar bodies. FSH, LH, and estrogen are necessary .
Male Reproductive System
1. Testes (paired)—located in the scrotum between the upper thighs; temperature in the scrotum is 96_F to permit production of viable sperm. Sperm are produced in seminiferous tubules and . A sperm cell consists of the head, which contains 23 chromosomes; the middle piece, which contains mitochondria; the flagellum for motility; and the acrosome on the tip of the head to digest the membrane of the egg cell
2. 2. Epididymis (paired)—a long coiled tube on the posterior surface of each testis. Sperm complete their maturation here.
3. Ductus deferens (paired)—extends from the epididymis into the abdominal cavity through the inguinal canal, over and down behind the urinary bladder to join the ejaculatory duct .Smooth muscle in the wall contracts in waves of peristalsis.
4. Ejaculatory ducts (paired)—receive sperm from the ductus deferens and the secretions from the seminal vesicles (see Fig. 20–3); empty into the urethra.
5. Seminal vesicles (paired)—posterior to urinary bladder; duct of each opens into ejaculatory duct . Secretion contains fructose to nourish sperm and is alkaline to enhance sperm motility.
6. Prostate gland (single)—below the urinary bladder,encloses the first inch of the urethra ; secretion is alkaline to maintain sperm motility; smooth muscle contributes to the force required for ejaculation.
7. Bulbourethral glands (paired)—below the prostate gland; empty into the urethra ; secretion is alkaline to line the urethra prior to ejaculation.
8. Urethra (single)—within the penis; carries semen to exterior . The penis contains three masses of erectile tissue that have blood sinuses. Sexual stimulation and parasympathetic impulses cause dilation of the penile arteries and an erection. Ejaculation of semen involves peristalsis of all male ducts and contraction of the prostate gland and pelvic floor.
9. Semen—composed of sperm and the secretions of the seminal vesicles, prostate gland, and bulbourethral glands. The alkaline pH (7.4) neutralizes the acidic pH of the female vagina.
Female Reproductive
1. Ovaries (paired)—located on either side of the uterus . Egg cells are produced in ovarian follicles; each ovum contains 23 chromosomes. Ovulation of a graafian follicle is stimulated by LH .
2. Fallopian tubes (paired)—each extends from an ovary to the uterus ; fimbriae sweep the ovum into the tube; ciliated epithelial tissue and peristalsis of smooth muscle propel the ovum toward the uterus; fertilization usually takes place in the fallopian tube.
3. Uterus (single)—superior to the urinary bladder and between the two ovaries.Myometrium is the smooth muscle layer that contracts for delivery . Endometrium is the lining which may become the placenta; basilar layer is permanent; functional layer is lost in menstruation and regenerated. Parts: upper fundus, central body, and lower cervix.
4. Vagina (single)—extends from the cervix to the vaginal orifice . Receives sperm during intercourse; serves as exit for menstrual blood and as the birth canal during delivery.Normal flora provide an acidic pH that inhibits the growth of pathogens.
5. External genitals —also called the vulva. The clitoris is a small mass of erectile tissue that responds to sexual stimulation; labia majora and minora are paired folds of skin that enclose the vestibule and cover the urethral and vaginal openings; Bartholin’s glands open into the vaginal orifice and secrete mucus.
Mammary Glands
1. Alveolar glands produce milk; lactiferous ducts converge at the nipple.
2. Hormonal regulation.
The Menstrual Cycle
1. Menstrual phase—loss of the endometrium.
2. Follicular phase—several ovarian follicles develop;ovulation is the rupture of a mature follicle; blood vessels grow in the endometrium.
3. Luteal phase—the ruptured follicle becomes the corpus luteum; the endometrium continues to develop.
4. If fertilization does not occur, decreased progesterone results in the loss of the endometrium in menstruation.
Gametogenesis
Gametogenesis is the process of formation of sex cells. It is said spermatogenesis in male & oogenesis in females. Both involve meiosis, a form of nuclear division.
Conception
Conception is the process of fertilization and subsequent establishment of pregnancy. Pregnancy begins with fertilization of an ovum and ends with delivery of the fetus after birth. When sperm is deposited in the vagina, the many spermatozoa wriggle about in all direction. Some travel in to the uterus and oviduct to meet the ova. If ova and sperm join this is called fertilization. From the day of fertilization on wards pregnancy starts.
Contraception
Contraception means protection. It has one aim, preventing pregnancy. This aim can be achieved by preventing sperm or ova not to function. It can be achieved by:
1. Preventing production
2. Preventing meeting of sperm & ova
3. Preventing implantation
Several methods are available, but can be grouped in to permanent & temporally methods.
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Topic 3: Continuation
Components of vascular system.
The vascular system consists of the:
1. Arteries,
2. Capillaries
3. Veins through which blood travels.
Arteries
1. Carry blood from the heart to capillaries; three layers in their walls.
2. Inner layer (tunica intima): simple squamous epithelial tissue (endothelium), very smooth to prevent abnormal blood clotting; secretes nitric oxide (NO), a vasodilator.
3. Middle layer (tunica media): smooth muscle and elastic connective tissue; contributes to maintenance of diastolic blood pressure (BP).
4. Outer layer (tunica externa): fibrous connective tissue to prevent rupture.
5. Constriction or dilation is regulated by the autonomic nervous system.
Veins and venules
1. Carry blood from capillaries to the heart; three layers in walls.
2. Inner layer: endothelium folded into valves to prevent the backflow of blood.
3. Middle layer: thin smooth muscle, because veins are not as important in the maintenance of BP.
4. Outer layer: thin fibrous connective tissue because veins do not carry blood under high pressure.
Anastomoses—connections between vessels of the same type
1. Provide alternate pathways for blood flow if one vessel is blocked.
2. Arterial anastomoses provide for blood flow to the capillaries of an organ (e.g., circle of Willis to the brain).
3. Venous anastomoses provide for return of blood to the heart and are most numerous in veins of the legs.
4.
Capillaries
1. Carry blood from arterioles to venules.
2. Walls are one cell thick (simple squamous epithelial tissue) to permit exchanges between blood and tissue fluid.
3. Oxygen and carbon dioxide are exchanged by diffusion.
4. BP in capillaries brings nutrients to tissues and forms tissue fluid in the process of filtration.
5. Albumin in the blood provides colloid osmotic pressure, which pulls waste products and tissue fluid into capillaries. The return of tissue fluid maintains blood volume and BP.
6. Precapillary sphincters regulate blood flow into capillary networks based on tissue needs; in active tissues they dilate; in less active tissues they constrict.
7. Sinusoids are very permeable capillaries found in the liver, spleen, pituitary gland, and red bone marrow to permit proteins and blood cells to enter or leave the blood.
Pathways of Circulation
1. Pulmonary: Right ventricle - pulmonary artery - pulmonary capillaries (exchange of gases) -pulmonary veins - left atrium.
2. Systemic: left ventricle - aorta - capillaries in body tissues - superior and inferior caval veins - right atrium
3. 3. Hepatic portal circulation: blood from the digestive organs and spleen flows through the portal vein to the liver before returning to the heart.Purpose: the liver stores some nutrients or regulates their blood levels and detoxifies potential poisons before blood enters the rest of peripheral.
Fetal Circulation
1. The placenta is the site of exchange between fetal blood and maternal blood.
2. Umbilical arteries (two) carry blood from the fetus to the placenta, where CO2 and waste products enter maternal circulation.
3. The umbilical vein carries blood with O2 and nutrients from the placenta to the fetus.
4. The umbilical vein branches; some blood flows through the fetal liver; most blood flows through the ductus venosus to the fetal inferior vena cava.
5. The foramen ovale permits blood to flow from the right atrium to the left atrium to bypass the fetal lungs.
6. The ductus arteriosus permits blood to flow from the pulmonary artery to the aorta to bypass the fetal lungs.
7. These fetal structures become nonfunctional after birth, when the umbilical cord is cut and breathing takes place.
Velocity of Blood Flow
1. Velocity is inversely related to the cross-sectional area of a segment of the vascular system.
2. The total capillaries have the greatest crosssectional area and slowest blood flow.
3. Slow flow in the capillaries is important to permit sufficient time for exchange of gases, nutrients, and wastes.
Blood Pressure (BP)—the force exerted by the blood against the walls of the blood vessels
1. BP is measured in mmHg: systolic/diastolic.Systolic pressure occurs during ventricular contraction; diastolic pressure occurs during ventricular relaxation.
2. Normal range of systemic arterial BP: 90 to 120/60 to 80 mmHg.
3. BP in capillaries is 30 to 35 mmHg at the arterial end and 12 to 15 mmHg at the venous end—high enough to permit filtration but low enough to prevent rupture of the capillaries.
4. BP decreases in the veins and approaches zero in the caval veins.
5. Pulmonary BP is always low (the right ventricle pumps with less force): 20 to 25/8 to 10 mmHg. This low BP prevents filtration and accumulation of tissue fluid in the alveoli.
Maintenance of Systemic BP
1. Venous return—the amount of blood that returns to the heart. If venous return decreases, the heart contracts less forcefully (Starling’s law) and BP decreases. The mechanisms that maintain venous return when the body is vertical are:
· Constriction of veins with the valves preventing backflow of blood
· Skeletal muscle pump—contraction of skeletal muscles, especially in the legs, squeezes the deep veins
· Respiratory pump—the pressure changes of inhalation and exhalation expand and compress the veins in the chest cavity
2. Heart rate and force—if heart rate and forceincrease, BP increases.
3. Peripheral resistance—the resistance of the arteries and arterioles to the flow of blood. These vessels are usually slightly constricted to maintain normal diastolic BP. Greater vasoconstriction will increase BP; vasodilation will decrease BP. In the body, vasodilation in one area requires vasoconstriction in another area to maintain normal BP.
4. Elasticity of the large arteries—ventricular systole stretches the walls of large arteries, which recoil during ventricular diastole. Normal elasticity lowers systolic BP, raises diastolic BP, and maintains normal pulse pressure.
5. Viscosity of blood—depends on RBCs and plasma proteins, especially albumin. Severe anemia tends to decrease BP. Deficiency of albumin as in liver or kidney disease tends to decrease BP. In these cases, compensation such as greater vasoconstriction will keep BP close to normal.
6. Loss of blood—a small loss will be rapidly compensated for by faster heart rate and greater vasoconstriction. After severe hemorrhage, these mechanisms may not be sufficient to maintain normal BP.
7. Hormones
a) Norepinephrine stimulates vasoconstriction, which raises BP;
b) Epinephrine increases cardiac output and raises BP;
c) ADH increases water reabsorption by the kidneys, which increases blood volume and BP;
d) Aldosterone increases reabsorption of Na_ ions by the kidneys; water follows Na_ and increases blood volume and BP;
e) ANP increases excretion of Na_ ions and water by the kidneys, which decreases blood volume and BP.
Distribution of Blood Flow
1. Metabolically active tissues require more oxygen,and receive a greater proportion of the blood volume as it circulates).
2. Blood flow is increased by the dilation of arterioles and precapillary sphincters.
3. In less active tissues, arterioles and precapillary sphincters constrict.
4. Organs receive sufficient oxygen, and BP for the body is maintained within the normal range.
Regulation of Blood Pressure
Intrinsic Mechanisms
1. The heart—responds to increased venous return by pumping more forcefully (Starling’s law), which increases cardiac output and BP.
2. The kidneys—decreased blood flow decreases filtration, which decreases urinary output to preserve blood volume. Decreased BP stimulates the kidneys to secrete renin, which initiates the reninangiotensin mechanism that results in the formation of angiotensin II, which causes vasoconstriction and stimulates secretion of aldosterone.
Nervous Mechanisms)
1. Heart rate and force
2. Peripheral resistance—the medulla contains the vasomotor center, which consists of a vasoconstrictor area and a vasodilator area. The vasodilator area brings about vasodilation by suppressing the vasoconstrictor area. The vasoconstrictor area maintains normal vasoconstriction by generating several impulses per second along sympathetic vasoconstrictor fibers to all arteries and veins. More impulses per second increase vasoconstriction and raise BP; fewer impulses per second bring about vasodilation and a drop in BP.
Click here to access Unit Eight Content.
Topic 1: Factors Influencing Nutrient Intake
Factors influencing nutrient intake
There are many physiological and psychological mechanisms affecting our daily patterns in consumption of food. Appetite is co-ordinated through the interaction of various complex systems within the body involving the gut and the brain. Genetic factors and the environment also have a role to play in food intake. The factors therefore include:
Physical activity: higher food intake is associated with increased physical activity. However, regular exercise will help regulate appetite and help limit excess food consumption.
Metabolism: people with naturally high metabolic rates have higher appetites. If you are dieting it is important to maintain your metabolic rate by eating and exercising regularly.
Hormones: there are many different hormones at play within the body – ghrelin is secreted by the stomach to tell you that you are hungry and insulin is secreted by the pancreas to tell you that you are full.
Temperature: cold climates has a tendency to be associated with an increase in appetite – this could be due to the body needing to warm itself up quickly, or because dark days mean that people are not getting enough sunlight which causes depression and people eat out of comfort.
Palatability: the tastier the food, the greater the pleasure derived from the food and the greater the appetite will be. On the other hand, it is argued that having food that is very bland will cause overeating because one does not feel satisfied from the food.
Psychology: stress and boredom often result in increased food intake. The best way of avoiding this is to exercise regularly – this will help you to relax and to reduce boredom.
Social influences: eating habits are often influenced by one’s upbringing – the three meals a day routine is often a cause for eating out habit rather than out of hunger. Many social events, such as Christmas celebrations, revolve around eating, drinking or both.
a growing child requires more calories per kg of body weight than an adult.
Sex: Males with high Basal Metabolic Rate (BMR) require more calories than females.
Activity: The type of activity also determines the energy requirements. The activities are classified as sedentary, moderate and heavy based on the occupation of an individual.
Physiological Stress: Nutrient requirements are increased in conditions of physiological stress such as pregnancy and lactation
Factors influencing food choice
Food choices for a balanced diet depend on many factors, such as:
Individual energy and nutrient needs- The amount of energy, carbohydrate, fat, protein, vitamins and minerals needed differs between different age groups and between males and females
Health concerns- Diets which exclude many foods due to a person’s health concerns or for medical reasons need to be planned carefully.
Cultural or religious practices-Ethical and religious practices, such as avoiding meat, may limit the range of foods people eat.
Cost- Cost of food is a particularly important factor for people with low incomes. Food prepared food at home is often cheaper than eating out or buying take-away.
Food availability- Most foods are grown in a particular season of the year. These are called ‘seasonal foods’. Buying foods when they are in season will often ensure the food price is lower.
Food preferences- Not everyone likes the same food, but some foods are particularly popular or unpopular. The taste, texture or appearance of foods can affect people in different ways.
Social considerations- Human welfare and fair trading, where growers or producers in developing countries are paid a good minimum price to cover their costs, can be a high concern for some people
Environmental considerations- Scientific intervention in the food chain also causes concerns for some people. Genetically modified (GM) ingredients changing a plant, animal or micro-organism's genes or inserting one from another organism. These foods are labeled so people may decide to choose non-genetically modified food products.
Advertising and other point of sale information- Advertisements encouraging people to choose certain foods often appear on the television, internet, radio, posters, magazines and newspapers. The point of purchase information and product placement are strategies often used to provide information to consumers. This can assist people in making healthier choices.
Click here to access Unit Eight Content.
Topic 2: Factors Influencing Nutrient Availability
The following sections will illustrate the different stages at which nutrient bioavailability can be influenced:
a) Effects of food matrix and chemical form of nutrients
The first step in making a nutrient bioavailable is to liberate it from the food matrix and turn it into a chemical form that can bind to and enter the gut cells or pass between them. Collectively this is referred to as bio accessibility. Nutrients are rendered bio accessible by the processes of chewing (mastication) and initial enzymatic digestion of the food in the mouth, mixing with acid and further enzymes in the gastric juice upon swallowing, and finally release into the small intestine, the major site of nutrient absorption. Here, yet more enzymes, supplied by the pancreatic juice, continue breaking down the food matrix.
b) Enhancers of nutrient bioavailability
Nutrients can interact with one another or with other dietary components at the site of absorption, resulting in either a change in bioavailability or if enhancers and inhibitors cancel each other out. Enhancers can act in different ways such as keeping a nutrient soluble or protecting it from interaction with inhibitors.
c) Impact of inhibitors on nutrient bioavailability
Inhibitors may reduce nutrient bioavailability by: binding the nutrient in question in a form that is not recognized by the uptake systems on the surface of intestinal cells, rendering the nutrient insoluble and thus unavailable for absorption, or competing for the same uptake system. Phytic acid is highly abundant in certain plant foods
d) Host factors
Internal or host-related factors can be subdivided into gastrointestinal and systemic factors. The role of gastrointestinal factors is illustrated by the absorptive pathway of vitamin B12. This vitamin requires gastric acid to be released from the food matrix and then it undergoes a sequence of binding to R protein, release from R protein, binding to the protein “intrinsic factor” (IF) and finally absorption of the intact IF-vitamin B12 complex in the lower intestine.
e) Impact on nutrient recommendations
For several nutrients – primarily calcium, magnesium, iron, zinc, folate and vitamin A – knowledge of their bioavailability is needed to translate physiological requirements into actual dietary requirements.
Click here to access Unit Eight Content.
Topic 3: Factors Affecting Nutrient Utilization
Factors Affecting Nutrient Utilization
Sickness
Nutrients can be lost because of illness. The illness may inhibit the absorption/drain the nutrients away through diarrhea and vomiting.
Bioavailability
Bioavailability indicates the amount of a nutrient that is absorbed in the intestine from the diet and is available to the body for its biological functions. The amount of a nutrient that is consumed is not fully absorbed and available for its metabolic function in the body. Bioavailability of a nutrient is governed by external and internal factors. Some nutrients enhance nutrient absorption while others hinder the absorption. The absorption rate of some nutrients can be enhanced when paired with other nutrients.
For instance, iron that is found in plant source is less bioavailable than iron found in animal sources. To enhance the absorption of iron, consume vitamin C alongside a serving of iron sources especially from vegetarian sources.
Vitamin C is a strong enhancer of iron absorption. This means having a glass of orange juice with a bowl of breakfast cereal helps the body use more of the iron in the cereal.
Inhibitors reduces nutrient bioavailability in three ways:
a. Binding the nutrient in question in form that is not recognized by the uptake systems on the surfaces of the intestinal cells
b. Rendering the nutrient insoluble and thus unavailable for absorption
c. Competing for the same uptake system e.g. interaction between calcium and non-haem iron.
d. Both minerals bind to a transporter on the surface of intestinal absorptive cells
Use of medication
Nutrient needs may be altered because of long-term medication use for instance use of drugs such as anticonvulsants and /phenobarbital for epilepsy, antacids, anti-inflammatory drugs, and laxatives can interfere with calcium and vitamin D absorption, which negatively influences bone metabolism
Alcohol affects the absorption of nutrients in a number of ways:
a) It acts as a diuretic, which promotes excretion of stored minerals like calcium, zinc and magnesium
b) Impairs nutrient absorption by damaging the cells lining the stomach and intestine and disabling the transport of some nutrients into the blood.
Biological value
Is a measure of the
proportion of absorbed protein from a food which becomes incorporated into the
proteins of the organism’s body. It captures how readily the digested protein
can be used in protein synthesis in the cells of an organism. When a protein
contains the essential amino acids in a proportion similar to that required by
the body, it has high biological value. When one or more essential amino acids
are missing or present in low numbers, the protein has low biological value.
Proteins from animal sources generally are of high biological value while those
from plant sources are of low biological value
Click here to access Unit Nine Content.
Topic 1: Factors Influencing Nutrient Intake
Factors influencing nutrient intake
There are many physiological and psychological mechanisms affecting our daily patterns in consumption of food. Appetite is co-ordinated through the interaction of various complex systems within the body involving the gut and the brain. Genetic factors and the environment also have a role to play in food intake. The factors therefore include:
Physical activity: higher food intake is associated with increased physical activity. However, regular exercise will help regulate appetite and help limit excess food consumption.
Metabolism: people with naturally high metabolic rates have higher appetites. If you are dieting it is important to maintain your metabolic rate by eating and exercising regularly.
Hormones: there are many different hormones at play within the body – ghrelin is secreted by the stomach to tell you that you are hungry and insulin is secreted by the pancreas to tell you that you are full.
Temperature: cold climates has a tendency to be associated with an increase in appetite – this could be due to the body needing to warm itself up quickly, or because dark days mean that people are not getting enough sunlight which causes depression and people eat out of comfort.
Palatability: the tastier the food, the greater the pleasure derived from the food and the greater the appetite will be. On the other hand, it is argued that having food that is very bland will cause overeating because one does not feel satisfied from the food.
Psychology: stress and boredom often result in increased food intake. The best way of avoiding this is to exercise regularly – this will help you to relax and to reduce boredom.
Social influences: eating habits are often influenced by one’s upbringing – the three meals a day routine is often a cause for eating out habit rather than out of hunger. Many social events, such as Christmas celebrations, revolve around eating, drinking or both.
a growing child requires more calories per kg of body weight than an adult.
Sex: Males with high Basal Metabolic Rate (BMR) require more calories than females.
Activity: The type of activity also determines the energy requirements. The activities are classified as sedentary, moderate and heavy based on the occupation of an individual.
Physiological Stress: Nutrient requirements are increased in conditions of physiological stress such as pregnancy and lactation
Factors influencing food choice
Food choices for a balanced diet depend on many factors, such as:
Individual energy and nutrient needs- The amount of energy, carbohydrate, fat, protein, vitamins and minerals needed differs between different age groups and between males and females
Health concerns- Diets which exclude many foods due to a person’s health concerns or for medical reasons need to be planned carefully.
Cultural or religious practices-Ethical and religious practices, such as avoiding meat, may limit the range of foods people eat.
Cost- Cost of food is a particularly important factor for people with low incomes. Food prepared food at home is often cheaper than eating out or buying take-away.
Food availability- Most foods are grown in a particular season of the year. These are called ‘seasonal foods’. Buying foods when they are in season will often ensure the food price is lower.
Food preferences- Not everyone likes the same food, but some foods are particularly popular or unpopular. The taste, texture or appearance of foods can affect people in different ways.
Social considerations- Human welfare and fair trading, where growers or producers in developing countries are paid a good minimum price to cover their costs, can be a high concern for some people
Environmental considerations- Scientific intervention in the food chain also causes concerns for some people. Genetically modified (GM) ingredients changing a plant, animal or micro-organism's genes or inserting one from another organism. These foods are labeled so people may decide to choose non-genetically modified food products.
Advertising and other point of sale information- Advertisements encouraging people to choose certain foods often appear on the television, internet, radio, posters, magazines and newspapers. The point of purchase information and product placement are strategies often used to provide information to consumers. This can assist people in making healthier choices.
Click here to access Unit Nine Content.
Topic 2: Factors Influencing Nutrient Availability
The following sections will illustrate the different stages at which nutrient bioavailability can be influenced:
a) Effects of food matrix and chemical form of nutrients
The first step in making a nutrient bioavailable is to liberate it from the food matrix and turn it into a chemical form that can bind to and enter the gut cells or pass between them. Collectively this is referred to as bio accessibility. Nutrients are rendered bio accessible by the processes of chewing (mastication) and initial enzymatic digestion of the food in the mouth, mixing with acid and further enzymes in the gastric juice upon swallowing, and finally release into the small intestine, the major site of nutrient absorption. Here, yet more enzymes, supplied by the pancreatic juice, continue breaking down the food matrix.
b) Enhancers of nutrient bioavailability
Nutrients can interact with one another or with other dietary components at the site of absorption, resulting in either a change in bioavailability or if enhancers and inhibitors cancel each other out. Enhancers can act in different ways such as keeping a nutrient soluble or protecting it from interaction with inhibitors.
c) Impact of inhibitors on nutrient bioavailability
Inhibitors may reduce nutrient bioavailability by: binding the nutrient in question in a form that is not recognized by the uptake systems on the surface of intestinal cells, rendering the nutrient insoluble and thus unavailable for absorption, or competing for the same uptake system. Phytic acid is highly abundant in certain plant foods
d) Host factors
Internal or host-related factors can be subdivided into gastrointestinal and systemic factors. The role of gastrointestinal factors is illustrated by the absorptive pathway of vitamin B12. This vitamin requires gastric acid to be released from the food matrix and then it undergoes a sequence of binding to R protein, release from R protein, binding to the protein “intrinsic factor” (IF) and finally absorption of the intact IF-vitamin B12 complex in the lower intestine.
e) Impact on nutrient recommendations
For several nutrients – primarily calcium, magnesium, iron, zinc, folate and vitamin A – knowledge of their bioavailability is needed to translate physiological requirements into actual dietary requirements.
Click here to access Unit Nine Content.
Topic 3: Factors Affecting Nutrient Utilization
Factors Affecting Nutrient Utilization
Sickness
Nutrients can be lost because of illness. The illness may inhibit the absorption/drain the nutrients away through diarrhea and vomiting.
Bioavailability
Bioavailability indicates the amount of a nutrient that is absorbed in the intestine from the diet and is available to the body for its biological functions. The amount of a nutrient that is consumed is not fully absorbed and available for its metabolic function in the body. Bioavailability of a nutrient is governed by external and internal factors. Some nutrients enhance nutrient absorption while others hinder the absorption. The absorption rate of some nutrients can be enhanced when paired with other nutrients.
For instance, iron that is found in plant source is less bioavailable than iron found in animal sources. To enhance the absorption of iron, consume vitamin C alongside a serving of iron sources especially from vegetarian sources.
Vitamin C is a strong enhancer of iron absorption. This means having a glass of orange juice with a bowl of breakfast cereal helps the body use more of the iron in the cereal.
Inhibitors reduces nutrient bioavailability in three ways:
a. Binding the nutrient in question in form that is not recognized by the uptake systems on the surfaces of the intestinal cells
b. Rendering the nutrient insoluble and thus unavailable for absorption
c. Competing for the same uptake system e.g. interaction between calcium and non-haem iron.
d. Both minerals bind to a transporter on the surface of intestinal absorptive cells
Use of medication
Nutrient needs may be altered because of long-term medication use for instance use of drugs such as anticonvulsants and /phenobarbital for epilepsy, antacids, anti-inflammatory drugs, and laxatives can interfere with calcium and vitamin D absorption, which negatively influences bone metabolism
Alcohol affects the absorption of nutrients in a number of ways:
a) It acts as a diuretic, which promotes excretion of stored minerals like calcium, zinc and magnesium
b) Impairs nutrient absorption by damaging the cells lining the stomach and intestine and disabling the transport of some nutrients into the blood.
Biological value
Is a measure of the
proportion of absorbed protein from a food which becomes incorporated into the
proteins of the organism’s body. It captures how readily the digested protein
can be used in protein synthesis in the cells of an organism. When a protein
contains the essential amino acids in a proportion similar to that required by
the body, it has high biological value. When one or more essential amino acids
are missing or present in low numbers, the protein has low biological value.
Proteins from animal sources generally are of high biological value while those
from plant sources are of low biological value
Click here to access Unit Ten Content.
Topic 1: Factors Influencing Nutrient Intake
Factors influencing nutrient intake
There are many physiological and psychological mechanisms affecting our daily patterns in consumption of food. Appetite is co-ordinated through the interaction of various complex systems within the body involving the gut and the brain. Genetic factors and the environment also have a role to play in food intake. The factors therefore include:
Physical activity: higher food intake is associated with increased physical activity. However, regular exercise will help regulate appetite and help limit excess food consumption.
Metabolism: people with naturally high metabolic rates have higher appetites. If you are dieting it is important to maintain your metabolic rate by eating and exercising regularly.
Hormones: there are many different hormones at play within the body – ghrelin is secreted by the stomach to tell you that you are hungry and insulin is secreted by the pancreas to tell you that you are full.
Temperature: cold climates has a tendency to be associated with an increase in appetite – this could be due to the body needing to warm itself up quickly, or because dark days mean that people are not getting enough sunlight which causes depression and people eat out of comfort.
Palatability: the tastier the food, the greater the pleasure derived from the food and the greater the appetite will be. On the other hand, it is argued that having food that is very bland will cause overeating because one does not feel satisfied from the food.
Psychology: stress and boredom often result in increased food intake. The best way of avoiding this is to exercise regularly – this will help you to relax and to reduce boredom.
Social influences: eating habits are often influenced by one’s upbringing – the three meals a day routine is often a cause for eating out habit rather than out of hunger. Many social events, such as Christmas celebrations, revolve around eating, drinking or both.
a growing child requires more calories per kg of body weight than an adult.
Sex: Males with high Basal Metabolic Rate (BMR) require more calories than females.
Activity: The type of activity also determines the energy requirements. The activities are classified as sedentary, moderate and heavy based on the occupation of an individual.
Physiological Stress: Nutrient requirements are increased in conditions of physiological stress such as pregnancy and lactation
Factors influencing food choice
Food choices for a balanced diet depend on many factors, such as:
Individual energy and nutrient needs- The amount of energy, carbohydrate, fat, protein, vitamins and minerals needed differs between different age groups and between males and females
Health concerns- Diets which exclude many foods due to a person’s health concerns or for medical reasons need to be planned carefully.
Cultural or religious practices-Ethical and religious practices, such as avoiding meat, may limit the range of foods people eat.
Cost- Cost of food is a particularly important factor for people with low incomes. Food prepared food at home is often cheaper than eating out or buying take-away.
Food availability- Most foods are grown in a particular season of the year. These are called ‘seasonal foods’. Buying foods when they are in season will often ensure the food price is lower.
Food preferences- Not everyone likes the same food, but some foods are particularly popular or unpopular. The taste, texture or appearance of foods can affect people in different ways.
Social considerations- Human welfare and fair trading, where growers or producers in developing countries are paid a good minimum price to cover their costs, can be a high concern for some people
Environmental considerations- Scientific intervention in the food chain also causes concerns for some people. Genetically modified (GM) ingredients changing a plant, animal or micro-organism's genes or inserting one from another organism. These foods are labeled so people may decide to choose non-genetically modified food products.
Advertising and other point of sale information- Advertisements encouraging people to choose certain foods often appear on the television, internet, radio, posters, magazines and newspapers. The point of purchase information and product placement are strategies often used to provide information to consumers. This can assist people in making healthier choices.
Click here to access Unit Ten Content.
Topic 2: Factors Influencing Nutrient Availability
The following sections will illustrate the different stages at which nutrient bioavailability can be influenced:
a) Effects of food matrix and chemical form of nutrients
The first step in making a nutrient bioavailable is to liberate it from the food matrix and turn it into a chemical form that can bind to and enter the gut cells or pass between them. Collectively this is referred to as bio accessibility. Nutrients are rendered bio accessible by the processes of chewing (mastication) and initial enzymatic digestion of the food in the mouth, mixing with acid and further enzymes in the gastric juice upon swallowing, and finally release into the small intestine, the major site of nutrient absorption. Here, yet more enzymes, supplied by the pancreatic juice, continue breaking down the food matrix.
b) Enhancers of nutrient bioavailability
Nutrients can interact with one another or with other dietary components at the site of absorption, resulting in either a change in bioavailability or if enhancers and inhibitors cancel each other out. Enhancers can act in different ways such as keeping a nutrient soluble or protecting it from interaction with inhibitors.
c) Impact of inhibitors on nutrient bioavailability
Inhibitors may reduce nutrient bioavailability by: binding the nutrient in question in a form that is not recognized by the uptake systems on the surface of intestinal cells, rendering the nutrient insoluble and thus unavailable for absorption, or competing for the same uptake system. Phytic acid is highly abundant in certain plant foods
d) Host factors
Internal or host-related factors can be subdivided into gastrointestinal and systemic factors. The role of gastrointestinal factors is illustrated by the absorptive pathway of vitamin B12. This vitamin requires gastric acid to be released from the food matrix and then it undergoes a sequence of binding to R protein, release from R protein, binding to the protein “intrinsic factor” (IF) and finally absorption of the intact IF-vitamin B12 complex in the lower intestine.
e) Impact on nutrient recommendations
For several nutrients – primarily calcium, magnesium, iron, zinc, folate and vitamin A – knowledge of their bioavailability is needed to translate physiological requirements into actual dietary requirements.
Click here to access Unit Ten Content.
Topic 3: Factors Affecting Nutrient Utilization
Factors Affecting Nutrient Utilization
Sickness
Nutrients can be lost because of illness. The illness may inhibit the absorption/drain the nutrients away through diarrhea and vomiting.
Bioavailability
Bioavailability indicates the amount of a nutrient that is absorbed in the intestine from the diet and is available to the body for its biological functions. The amount of a nutrient that is consumed is not fully absorbed and available for its metabolic function in the body. Bioavailability of a nutrient is governed by external and internal factors. Some nutrients enhance nutrient absorption while others hinder the absorption. The absorption rate of some nutrients can be enhanced when paired with other nutrients.
For instance, iron that is found in plant source is less bioavailable than iron found in animal sources. To enhance the absorption of iron, consume vitamin C alongside a serving of iron sources especially from vegetarian sources.
Vitamin C is a strong enhancer of iron absorption. This means having a glass of orange juice with a bowl of breakfast cereal helps the body use more of the iron in the cereal.
Inhibitors reduces nutrient bioavailability in three ways:
a. Binding the nutrient in question in form that is not recognized by the uptake systems on the surfaces of the intestinal cells
b. Rendering the nutrient insoluble and thus unavailable for absorption
c. Competing for the same uptake system e.g. interaction between calcium and non-haem iron.
d. Both minerals bind to a transporter on the surface of intestinal absorptive cells
Use of medication
Nutrient needs may be altered because of long-term medication use for instance use of drugs such as anticonvulsants and /phenobarbital for epilepsy, antacids, anti-inflammatory drugs, and laxatives can interfere with calcium and vitamin D absorption, which negatively influences bone metabolism
Alcohol affects the absorption of nutrients in a number of ways:
a) It acts as a diuretic, which promotes excretion of stored minerals like calcium, zinc and magnesium
b) Impairs nutrient absorption by damaging the cells lining the stomach and intestine and disabling the transport of some nutrients into the blood.
Biological value
Is a measure of the
proportion of absorbed protein from a food which becomes incorporated into the
proteins of the organism’s body. It captures how readily the digested protein
can be used in protein synthesis in the cells of an organism. When a protein
contains the essential amino acids in a proportion similar to that required by
the body, it has high biological value. When one or more essential amino acids
are missing or present in low numbers, the protein has low biological value.
Proteins from animal sources generally are of high biological value while those
from plant sources are of low biological value