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Introduction to the Physiology of Human Body

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1. Define anatomy and physiology
While anatomy provides us with a static image of the body architecture, physiology reveals the body’s dynamic and animated workings. Physiology often focuses on events at the cellular or molecular level.
A. Anatomy – studies the structure of the body parts and their relationship to one another.
i. Developmental – concerns structural changes that in the body occur throughout the lifespan. Embryology studies the developmental changes that occur before birth. ii. Microscopic – deals with structures too small to be seen by the naked eye. Cytology studies the cells of the body and histology studies the tissues. iii. Macroscopic/Gross – the study of large body structures visible to the naked eye, such as the heart, lungs, and kidneys. Gross anatomy ca be approached in different ways, such as Systemic (body structure is studied by systems), Regional (by particular region) or surface (internal structures as the relate to the overlying skin surface).

B. Physiology – concerns the function of the body, how the body works and carry out their life-sustaining activities.
i. Renal physiology – concerns kidney function and urine production. ii. Neurophysiology – explains the workings of the nervous system. iii. Cardiovascular physiology – examines the operation of the heart and blood vessels.
2. Levels of structural organisation
A. Chemical Level – the simplest level includes atoms, building blocks, which combine to form molecules, like water. Molecules then combine to form organelles, the internal organs of cells.
B. Cellular Level – made up of cells, the smallest unit of living matter. Individual cells have some common functions, but vary is size and shape. Different types of cells carry out different functions.
C. Tissue Level – tissues are groups of cells that have a common function. The four basic types of tissue in humans, (epithelium, connective, muscle and nervous), each have a characteristic role in the body.
D. Organ Level – an organ is a structure of at least two different tissue types that perform a specific function with the body, such as the brain, liver, etc. Functions begin to emerge at this level.
E. Organ System Level – one or more organs work together to achieve a common purpose. For example, the heart and blood vessels work together to circulate blood around the body, providing oxygen and nutrients to cells.
F. Organismal Level – the highest level of organisation, is the sum of all structural levels working together.
3. functions of the major organs systems
The human body is made up of 11 organ systems that work with one another interdependently.
A. Integumentary – forms the external body covering and protects deeper tissues from injury, synthesizes vitamin D, and houses cutaneous receptors and sweat/oil glands. (Hair, skin, nails, etc.).
B. Skeletal – protects and supports internal organs and provides a framework the muscles use to cause movement. Blood cells are formed within bones and bones store minerals.
C. Muscular – allows manipulation of the environment, locomotion and facial expression, maintains posture and produces heat. (Skeletal, cardiac and smooth)
D. Nervous – the fast acting control system of the body that responds to internal and external changes by activating appropriate muscles and glands. (Spine, nerves and brain)
E. Endocrine – glands secrete hormones that regulate processed such as growth, reproduction and metabolism by body cells. (Thyroid, pituitary, pineal, adrenal, pancreas, ovary and testis).
F. Cardiovascular – blood vessels transport blood, which carries oxygen, carbon dioxide, nutrients, wastes, etc. The heart pumps blood around the body. (Blood vessels and the heart)
G. Lymphatic/Immune – picks up the fluid leaked from blood vessels and returns it to blood. Disposes of debris in the lymphatic system. Houses white blood cells (lymphocytes) involved in immunity. (Lymphatic vessels, thymus, thoracic duct, red bone marrow, lymph nodes, etc.).
H. Respiratory – keeps blood constantly supplied with oxygen and removes carbon dioxide. The gaseous exchanges occur through the walls of the air sacs of the lungs. (Lung, trachea, larynx, bronchus, etc.).
I. Digestive – breaks down food into absorbable units that enter the blood for distribution to body cells. Indigestible foodstuffs are eliminated. (Liver, small/large intestines, oesophagus, rectum, etc.).
J. Urinary – eliminates nitrogenous wastes from the body. Regulates water, electrolyte and acid-base balance of the blood. (kidney, bladder, urethra, etc.).
K. Reproductive – overall function is production of offspring. Testis produce sperm and male ducts/glands aid in delivery of sperm to the female reproductive tract. Ovaries produce eggs and the remaining female structure serve as sites for fertilisation and development of foetus. Mammary glands of the female breasts produce milk to nourish the newborn. (Penis, testis, scrotum, prostate gland, etc. for males and ovary, uterus, vagina, mammary glands, etc. in females).m
4. Major body cavities and their subdivisions
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A. Dorsal Body Cavity – protects the nervous system’s organs.
i. Cranial – protects the skull, encasing the brain. ii. Vertebral – runs within the vertebral column, enclosing the spinal cord.
B. Ventral Body Cavity – the larger cavity houses internal organs as a group called the viscera.
i. Thoracic – surrounds the ribs and muscles of the chest. This cavity is further divided into the pleural cavity (enveloping the lung) and the medial mediastinum cavity (encloses the heart, and surrounding organs like oesophagus, trachea, etc.). ii. Abdominopelvic – the inferior cavity separated from the thoracic cavity by the diaphragm. It’s superior portion, the abdominal cavity contains the stomach, intestines, liver and other organs located in the abdomen and the inferior pelvic cavity contains the urinary bladder, reproductive organs, and the rectum.
5. Major classes of organic molecules and their functions
A. Carbohydrates – (glucose, glycogen, etc.) a group of molecules composed of carbon, hydrogen and oxygen and include sugars and starches. The major function of carbohydrates in the body is to provide a source of cellular fuel. Carbs can be classified and according to size and solubility.
i. Monosaccharides – (single sugars) single structures containing 3 - 7 carbon atoms. Often occur in the ratio 1:2:1, so the general formula for monosaccharides is (CH2O). For example, glucose has 6 carbon atoms and its molecular formula is (C6H12O6) and ribose, with 5 carbon atoms, is (C5H10O5). Monosaccharides are named according to the number of carbon atoms they contain. ii. Disaccharides – (double sugars) are formed when two monosaccharides are joined by dehydration synthesis (a water molecule is lost as the bond is made). For example, lactose and sucrose. Disaccharides are too large to pass through cell membranes, therefore have to be digested to their simple sugar units to be absorbed from the digestive tract into the blood. iii. Polysaccharides – (many sugars) a large number of simple sugars linked together by dehydration synthesis. There are two polysaccharides that are important in the body; starch (long, linear chains of glucose used to store energy) and glycogen (storage carbohydrate of animal tissue, stored primarily in the skeletal muscle and liver cells).
B. Lipids – (fats and oils) insoluble in water but easily dissolve in other lipids and organic solvents such as alcohol. Like carbohydrates, all lipids contain carbon, hydrogen and oxygen.
i. Triglycerides – (neutral fats) composed of fatty acids (linear chains of carbon and hydrogen atoms) and glycerol (modified simple sugar). They provide the body’ most efficient and compact form of stored energy and are mainly found beneath the skin. ii. Phospholipids – are modified triglycerides and are used as the main material for building cellular membrane and prevalent in nervous tissue. Participate in the transport of lipids in plasma. iii. Steroids – fat soluble molecules made of four interlocking hydrocarbon ring that contain little oxygen. Cholesterol (ingested in animal product such as eggs, meat, etc.) is the most important molecule in steroid chemistry and is essential for synthesis of steroid hormones.
C. Proteins – (enzymes, sucrose, lactose, keratin, collagen, etc.) large complex molecules made up of amino acids that have many critical roles in the body. They do most of the work in cells and are required for the structure, function and regulation of the body’s tissues and organs. Proteins can be described in four structural levels:
D. Nucleic Acids (DNA and RNA) – the largest molecules in the body. DNA (deoxyribonucleic acid) and RNA (ribonucleic acid) are made from monomers known as nucleotides (building block of nucleic acids). Nucleotides function to carry out energy within the cell in the form of nucleoside triphosphates (ATP, GTP, CTP and UTP).
6. define and explain the importance of homeostasis
Homeostasis is the body’s ability to maintain reasonably stable internal conditions even though the external environment change continuously. Almost every organ system plays a role in maintaining the constancy of the internal environment. Adequate blood levels of vital nutrients must be continuously present, and heart activity and blood pressure must be constantly monitored and adjusted so that the blood is propelled to all body tissues. Wastes must not be allowed to accumulate, and body temperature must be precisely controlled.
A. Homeostatic Control
i. Negative Feedback Mechanisms – the output shuts off the original effect of the stimulus or reduces its intensity. These mechanisms cause the variable to change in a direction opposite to that of the initial change, hence the name. ii. Positive Feedback Mechanisms – the result or response enhances the original stimulus so that the response in accelerated. This feedback mechanism is positive because the change that results proceeds in the same direction as the initial change, causing the variable to deviate further from its original value or range.
B. Homeostatic Imbalance – can occur when interruptions to the homeostatic state become long term, and can not be easily fixed. There are a number of things that can cause homeostatic imbalance, but an easily recognised one is disease. A variety of diseases can result from a homeostatic imbalance, such as diabetes, dehydration, hypoglycaemia/hyperglycaemia, and any disease resulting from bloodstream toxins. Long term illnesses that disrupt the body’s ability to function properly make it unlikely for the body to return to a homeostatic state.

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