Lecture 1: Human Physiology PDF

A. B I O 2: ANIMAL PHYSIOLOGY LECTURE 1: 3. Set Point: Ideal fluid levels the body aims to maintain. HUMAN PHYSIOLOGY...

A. B I O 2: ANIMAL PHYSIOLOGY LECTURE 1: 3. Set Point: Ideal fluid levels the body aims to maintain. HUMAN PHYSIOLOGY 4. Affector Signals: Hormones like Antidiuretic Hormone (ADH) help retain water. I. AT THE CELLULAR LEVEL Sodium Potassium pump / sodium pump Water Input/Output ⚫ found in all cells Input: 1. Ingested (drinks/food). ⚫ responsible for establishing the gradient across the plasma 2. Generated from metabolism. membrane Gradient provides energy for several essential cell functions Output: 1. Lungs (water vapor). In the clinic: 2. Skin (sweat). Cystic Fibrosis 3. GI tract (feces). ⚫ Autosomal recessive disease characterized by 4. Kidneys (urine). 1. Chronic lung inf ections, 2. Pancreatic insuf f iciency In the Clinic: 3. Inf ertility among men Neurological Procedures & Cerebrovascular accidents ⚫ common among white (CVA-Strokes) ⚫ most common lethal genetic disease = mutation / deletion of ⚫ Of ten results in the accumulation of the interstitial fluid in the chromosome 7, thus the degradation of the protein by the ER brain (edema) and swelling of neurons is altered and the transporter does not reached plasma ⚫ Brain is enclosed within the skull & Edema can raise the membrane intracranial pressure, disrupt neuronal f unction which leads to coma and death Number of Microbial cells versus human cells ❖ 10:1 - Microbial cells: Human Cell REGULATION OF GLUCOSE ◼ 100 trillion microbial cells ◼ 2-6 pounds of body weight ❖ Microbe - any living thing that cannot be seen with the naked eye (f or example, bacteria, viruses, f ungi, and protozoa). ❖ Human Microbiome Project - largest study in October 2007 by national institute of health ❖ Microbiota ◼ total population of microbial cells on human body ◼ includes so-called “good” bacteria that do not cause disease and may even help us. it also includes pathogenic ❖ Microbiome - combination of these microbial cells & their genes ❖ 5 signif icant regions of the human body were examined: ◼ airway, skin, mouth, gastrointestinal tract, & vagina. II. HOMEOSTASIS ⚫ existence & maintenance of a relatively constant environm ent within the body despite f luctuations in either the external environment or the internal environment. ⚫ Most body cells are surrounded by a small amount of f luid, and normal cell f unctions depend on the maintenance of the cells’ f luid environment within a narrow range of conditions, including temperature, volume, and chemical content which are called variables as their values can change. The regulation of glucose in the body Volume and Composition of Body Fluid Compartments Whole Body Steady-------------------------------------------------State Balance 1. Blood glucose normal range Ef f ector signal-------------------CNS Sensor--------------------Af f ector signal 2. Blood Glucose Levels Rise: After eating, carbohydrates are broken down Thirst------------------------ Set Point=body f luid ---------------ADH into glucose (Homeostasis Disturbed) Osmolality (anion-cation) Antidiuretic Hormone 3. Pancreatic islets detect an increase in blood glucose and secrete insulin. Water Input ----------------------------------------- Water Output (Action) 1. Ingested (liquid, in f ood). 1. Lungs 4. Insulin stimulates glucose uptake by most tissues and promotes glycogen 2. Generated f rom Cellular metabolism 2. Skin storage in skeletal muscle and liver. Excess glucose is stored as lipids in 3. GI Tract adipose tissue. (Reaction) 4. Kidneys 5. Blood glucose level decreases (Homeostasis Restored) Body Fluid Balance: The body adjusts fluid intake and output to maintain 1. Blood glucose normal range balance, keeping osmolality stable. 2. Blood glucose level decreases (Homeostasis disturbed) 3. Pancreatic islets detect a decrease in blood glucose and do not secret Compartments: insulin (Action) Intracellular Fluid (ICF): Inside cells. 4. Decreased insulin result in decreased glucose uptake, increase glycogen Extracellular Fluid (ECF): Outside cells (including plasma). breakdown by the liver and skeletal muscle, and increased glucose synthesis Steady-State Balance (Reaction) 1. Effector Signals: Thirst indicates the need for water. 5. Blood glucose level increases (homeostasis restored) 2. CNS Sensors: Detect changes in fluid levels (like increased osmolality). A. B I O 2: ANIMAL PHYSIOLOGY LECTURE 2 Positive Feedback Clinical Impacts: CADAVER AND THE LAW ⚫ Cadavers - bodies of people who have died used by anatomists to study of human bodies f or medical education, & history, What it is: Increases a response. ⚫ Early 1800s - arose the resurrectionists, or body snatchers removed bodies f rom graves & provided them to medical schools. Example: During childbirth, the body releases a hormone ⚫ William Burke and William Hare that makes contractions stronger, leading to more ◼ murdered 17 people in Scotland & sold their bodies to hormone release until the baby is born. medical school. ◼ When discovered, Hare testif ied against Burke & went f ree. Burke was convicted, hanged, and publicly dissected. Negative Feedback ◼ Led to establish laws regulating the acquisition of cadavers ⚫ Uniform Anatomical Gift Act allows individuals to donate their What it is: Decreases a response to maintain balance. organs or entire cadaver by a notation on their driver’s license. Humors and Homeostasis Example: If you get too hot, your body sweats to cool ⚫ body maintains a balance (homeostasis) date back to ancient down. If you get too cold, you shiver to warm up. Greece. ⚫ Early physician ◼ Body supported 4 juices, or humors ◆ red juice of blood, ◆ yellow juice of bile, ◆ white juice secreted f rom nose & lungs, ◆ black juice in pancreas. ◼ They also thought health resulted f rom proper balance of these juices ◼ excess of any one of them caused disease. ⚫ Normally, they believe, the body would attempt to heal itself by expelling excess juice, as when mucus runs f rom the nose of a person with cold. ⚫ This belief led to the practice of bloodletting to restore the body’s normal balance of juices. ◼ led to practice of bloodletting to restore the body’s normal balance of juices using sharped instrument or applied leeches BLOOD LETTING th th ⚫ In 18 and 19 centuries ◼ barbers conducted the actual procedure (red-and-white- striped barber pole originated as bloodletting symbol) ◆ top brass basin = leeches; bottom = collecting blood; stripes = bandages used as tourniquets; pole = stood f or the wooden staf f patients gripped ◆ Didn’t improve patient’s condition was taken as evidence that not enough blood had been removed to restore healthy body’s juices balance ⚫ Phlebotomy - modern term f or bloodletting; ◼ practiced in a controlled setting & removes only small volumes of blood f or lab testing. ⚫ Polycythemia - overabundance of RBCs; bloodletting is still usef ul but doesn’t continue until the patient f aints or dies Positive versus Negative Feedback Mechanism A. B I O 2: ANIMAL PHYSIOLOGY LECTURE 3 ◼ Hypogastric BODY POSITIONS ◼ Right and lef t iliac DIRECTIONAL TERMS ✓ Anatomical position: person standing erect with f ace directed PLANES forward, the upper limbs hanging to the sides, & palms of the hands f acing f orward. Sagittal plane (f light of an arrow) ✓ Supine position when person lying f ace upward ⚫ runs vertically through the body & separates it into right & left ✓ Prone position when person lying f ace downward parts; split by an arrow passing anteriorly to posteriorly ✓ Body position can aff ect the description of body parts relative to Median plane each other. ⚫ a sagittal plane that passes through the midline of the body, ✓ In anatomical position, the elbow is above the hand, but in the dividing it into equal right & left halves. supine or prone position, elbow and hand are at the same level. Transverse plane, or horizontal plane ✓ To avoid confusion, relational descriptions are always based on ⚫ runs parallel to the surf ace of the ground, dividing the body into the anatomical position, no matter the actual position of the superior & inferior parts. body. Frontal plane, or coronal ; crown plane ⚫ runs vertically f rom right to lef t and divides the body into anterior Directional terms describe parts of the body relative to each other & posterior parts. ⚫ Right & left are used as directional terms in anatomical term. ⚫ Up replaced by superior, down by inferior, front by anterior, and back by posterior. ⚫ Anterior means that which goes before; Ventral means belly. ◼ Theref ore, anterior surf ace of the human body is also called ventral surface / belly, as belly “goes f irst” when walking. ⚫ Posterior means that which follows, and Dorsal means back. ◼ Thus, posterior surf ace of the body is dorsal surface / back, which f ollows as we are walking. ⚫ Proximal means nearest, whereas distal means distant. ◼ For linear structures like limbs = one end is near & other end is f arther away. ◼ Each limb is attached at its proximal end to the body, and the distal end, such as the hand, is f arther away. ⚫ Medial: toward the midline; lateral: away f rom the midline ◼ The nose is located in a medial position on the f ace, and the ears are lateral to the nose. ⚫ Superficial : structure close to the surf ace of the body; and Deep is toward the interior of the body. ◼ For example, the skin is superf icial to muscle and bone LONGDITUDINAL TRANSVERSE OBLIQUE ⚫ Organs are of ten sectioned to reveal their internal structure. Healt h prof essionals use a number of terms when ref erring to diff erent ⚫ Longitudinal section: cut through long axis of organ is regions or parts of the body. ⚫ Transverse / cross section: cut at a right angle to long axis ⚫ Central region of the body: head, neck, and trunk. ⚫ TRUNK: divided into thorax (chest), abdom en (region bet thorax & pelvis), pelvis (inf erior end of trunk associated w/ hips). ⚫ Upper limb is divided into the arm, forearm, wrist, & hand. ◼ Arm extends f rom shoulder to elbow, & forearm extends f rom elbow to wrist. ⚫ Lower limb is divided into the thigh, leg, ankle, and foot. ◼ Thigh extends f rom hip to knee, & leg extends f rom knee to ankle. ✓ Note that, contrary to popular usage, the terms arm and leg ref er to only a part of the respective limb. QUADRANTS ⚫ Abdomen is often subdivided superf icially into 4 section/ quadrants, by 2 imaginary lines, 1 horizontal & 1 vertical that intersect at the navel ◼ Right-upper, ◼ Lef t-upper, ◼ Right-lower, and ◼ Lef t-lower quadrants REGIONS ⚫ Abdomen is sometimes subdivided into by 4 imaginary lines: 2 horizontal and 2 vertical. ⚫ 4 lines create an imaginary tic-tac-toe figure on the abdomen, resulting in (9) nine regions: ◼ Epigastric ◼ Right and lef t hypochondriac ◼ Umbilical ◼ Right and lef t lumbar, A. B I O 2: ANIMAL PHYSIOLOGY LECTURE 4 LUNGS AND PLEURA BODY CAVITIES, SEROUS MEMBRANES, MESENTERIES ⚫ The body contains many cavities. Some of these cavities, such as nasal cavity, open to the outside of the body, & some do not. 3 TRUNK CAVITIES THORACIC CAVITY ⚫ surrounded by the rib cage and is separated f rom the abdominal cavity by the muscular diaphragm ⚫ Mediastinum ◼ median structure divided thoracic cavity into right & lef t parts ◼ partition containing heart, thymus, trachea, esophagus, & other structures. ◼ 2 lungs are located on each side of the mediastinum. The abdominal and pelvic cavities are not physically separated and sometimes are called the ABDOMINOPELVIC CAVITY. PELVIC CAVITY ⚫ small space enclosed by the bones of pelvis & contains urinary VISCERAL PERITONEUM bladder, part of large intestine, & internal reproductive organs. ABDOMINAL CAVITY ⚫ bounded primarily by the abdominal muscles & contains stomach, intestines, liver, spleen, pancreas, and the kidneys. TRUNK CAVITIES CLINICAL CASE ON POINT: PERITONITIS Appendicitis ⚫ most common cause of emergency abdominal surgery in children with symptoms of pain in RLQ and f ever ⚫ appendix inf ection can rupture its wall (visceral peritoneum) releasing into the peritoneal cavity ⚫ Thus, leads to peritonitis if not treated MESENTERIES SEROUS MEMBRANES ⚫ Consist of 2 layers of peritoneum f used together connect visceral ⚫ They lined the trunk cavities & cover the organs of these peritoneum of some abdominopelvic organs to parietal cavities. peritoneum on body wall or to visceral peritoneum of other ⚫ Cavi ty or space, bet visceral & parietal serous membranes is abdominopelvic organs. normally f illed with a thin, lubricating f ilm of serous fluid ⚫ Anchor organs to the body wall & provide a pathway f or nerves produced by the membranes and blood vessels to reach the organs. ⚫ As an organ rubs against another organ or against the body wall, ⚫ Other abdominopelvic organs are more closely attached to the serous fluid & smooth serous membranes reduce friction body wall and do not have mesenteries. ⚫ Thoracic cavity contains 3 serous membrane-lined cavities: 1 pericardial cavity (heart) & 2 pleural cavities (lungs) RETROPERITONEAL BODY CAVITIES ⚫ Parietal peritoneum covers these other organs, which are said to ⚫ Visceral pericardium covers heart, which is contained within a be retroperitoneal (behind). connective tissue sac lined with the parietal pericardium ⚫ Retroperitoneal organs includes: ⚫ Pericardial cavity, which contains pericardial fluid, is located ◼ Kidneys, adrenal glands, pancreas, parts of the intestines, bet. visceral pericardium and the parietal pericardium and urinary bladder ⚫ Parietal peri cardium: outer layer, f irmly attached to f ibrous pericardium HEART AND PERICARDIUM A. B I O 2: ANIMAL PHYSIOLOGY LECTURE 5 ✓ Reproductive hormone secretion gradually declines in elderly INFLAMMATION AND TISSUE REPAIR men, and women experience menopause ✓ Secretion of thymosin f rom the thymus decreases with age. Glucose regulation vs. Hormones ✓ Fewer f unctional lymphocytes are produced, and the immune ⚫ Insulin and Glucagon together regulate blood glucose levels system becomes less eff ective in protecting the body against ⚫ ↑ blood glucose levels, ↑ insulin secretion, ↓ glucagon secretion inf ections and cancer. ⚫ ↓ blood glucose levels, ↓ insulin secretion, ↑ glucagon secretion ✓ Parathyroid hormone secretion increases to maintain blood calcium levels if dietary Ca2+ and vitamin D levels decrease, as Hormones they of ten do in the elderly. Consequently, a substantial ⚫ Epinephrine, cortisol, & growth hormone maintain blood levels of decrease in bone matrix may occur. nutrients. ✓ In most people, the ability to regulate blood glucose does not ⚫ When blood glucose levels decrease, these hormones are decrease with age. secreted at a greater rate. ✓ However, there is an age-related tendency to develop type 2 ⚫ Epinephrine and cortisol cause the breakdown of protein and diabetes mellitus for those who have a f amilial tendency, and it is lipids and the synthesis of glucose to help increase blood levels correlated with age-related increases in body weight of nutrients. ⚫ Growth hormone slows protein breakdown and f avors lipid CLINICAL CASE ON POINT: Hyperthyroidism (Graves’ disease) breakdown ⚫ Symptoms for over several months ◼ Sweating excessively and appeared f lushed CLINICAL CASE ON POINT: ◼ heart pounding, much more nervous than usual Type 2 Diabetes Mellitus ◼ dif f icult to concentrate ⚫ results f rom reduced sensitivity of tissues to the eff ects of insulin ◼ f eel weak and lose weight, even her appetite was greater because of abnormal insulin receptor or abnormal responses to than normal the insulin receptors. ◼ eyes seemed larger than usual ⚫ Consequently, insulin is less able to f acilitate the entry of ⚫ Treatment: Removal of part of the thyroid gland glucose into the liver, skeletal muscles, and adipose tissues ◼ Caus ed by the elevated secretion of thyroid hormones f rom ⚫ Intervention: restricting f ood intake, especially carbohydrates the thyroid gland (alterations in hormone secretion) and f ats, and increasing exercise ◼ Approx 95% of Graves disease cases ⚫ Common signs of high blood glucose levels: f requent ◆ immune system produces an unusual antibody type inf ections, changes in vision, & f atigue that binds to receptors on the cells of thyroid follicle and stimulates increased amounts of thyroid hormone. Diabetes insipidus ◆ The secretion of the releasing hormone and thyroid- ⚫ Normal blood glucose levels but kidneys can't properly stimulating hormone is inhibited by elevated thyroid concentrate urine resulting to excessive water loss at kidneys hormones. however, the antibody is produced in large ⚫ Might caused by amounts and is not inhibited by thyroid hormones. A ◼ Malf unction of either of these types of proteins could disrupt very elevated rate of thyroid hormone secretion is water homeostasis. theref ore maintained. ◼ ADH: chemical signal that regulat es water loss f rom ◆ size of thyroid gland increases, & connective tissue kidneys. components are deposited behind eyes, causing them ◼ If receptor molecules f or ADH are altered & not f unctioning to bulge. properly, the kidney cells could not respond to the signal. ◆ Enlargement of the thyroid gland is called a goiter. ◼ Or water membrane channels, which allow water to move ◆ treated with radioactive iodine (131i) atoms that were across cell membrane, are not f unctioning properly and are actively transported into thyroid cells, where they disrupting water homeostasis. destroyed a substantial portion of the thyroid gland. ◼ Other treatment AGE VS. ENDOCRINE SYSTEM 1. drugs that inhibit synthesis & secretion of thyroid hormones and 2. surgery to remove part of the thyroid gland. Pituitary gland "master" gland of the endocrine system ✓ age related changes to the endocrine system include the gradual decrease in the secretion of some, but not all, endocrine glands ✓ Some of the decreases in secretion may be due to the f act that older people commonly engage in less physical activity. ✓ GH secretion decrease as people age, greatest in those who don’t exercise & may not occur at all in older people who exercise regularly ✓ Decreasing GH levels may explain the gradual decrease in bone and muscle mass and the increase in adipose tissue seen in many elderly people. So f ar, administering GH to slow or prevent the consequences of aging has not been f ound to be eff ective, and unwanted side ef f ects are possible. ✓ A decrease in melatonin secretion may inf luence age- related changes in sleep patterns, as well as the decreased secretion of some hormones, such as GH and testosterone. ✓ The secretion of thyroid hormones decreases slightly with age. Age-related damage to the thyroid gland by the immune system can occur. ✓ Approximately 10% of elderly women experience some reduction in thyroid hormone secretion; this tendency is less common in men. ✓ The kidneys of the elderly secret e less renin, reducing the ability to respond to decreases in blood pressure. A. B I O 2: ANIMAL PHYSIOLOGY CELLULAR INJURY AND SKIN CANCER INJECTIONS ⚫ Cancers developed in response to Chronic Tissue Injury 1. Intradermal injection ◼ Caus ed by variety of stress that a cell suff ers due to ⚫ drawing the skin taut & inserting a small needle at a shallow external and internal environmental changes angle into the dermis (eg. tuberculin skin test) ◼ Injuries cannot cause cancer but leads to f inding cancer in 2. Subcutaneous injection the injured area ⚫ pinching skin to form a “tent” & inserting a short needle into adipose tissue of the subcutaneous tissue (eg. insulin injection) ⚫ Skin cancer 3. Intramuscular injection - most common type of cancer ⚫ inserting a long needle at a 90° angle to the skin into a muscle - Chemicals and radiation (x-rays) are known to induce cancer, deep to the subcutaneous tissue (eg. most vaccines, antibiotics) associated with exposure to ultraviolet (UV) light - develop on the f ace, neck, or hands Skin Color and Exposure to Sunlight ◼ Vulnerable group: ⚫ The evolution of skin color in humans is intriguing because it ◆ f air-skinned (they have less protection f rom sun) helps explain certain modern health problems. During human ◆ older than 50 (have had long exposure to the sun) evolution, the skeletal system of our ancestors changed, resulting in an upright posture and the ability to walk and run 3 Main Types of Skin Cancer greater distances. 1. Basal cell carcinoma ⚫ As a result of increased physical activity, excess heat is ⚫ most f requent type produced, which can cause overheating. An increase in the ⚫ Begins with cells in stratum basale & extends into dermis to number of sweat glands in the skin and a reduction in the produce an open ulcer amount of hair covering the skin help eliminate the excess ⚫ little danger that this type of cancer will spread, or metastasize to heat. other areas of the body. ⚫ With the reduction in hair over most of the body, prolonged ⚫ Cure: surgical removal or radiation therapy exposure of the skin to sunlight can be harmful in two ways. ✓ Stratum basale - deepest layer of your epidermis f irst, it promotes the development of skin cancer by damaging DNA; second, it decreases the levels of the B vi tamin folate 2. Squamous cell carcinoma in the blood by breaking it down through a photochemical ⚫ Develops f rom cells immediately superf icial to stratum Basale reaction. ⚫ Physio - cells undergo little or no cell division; Pathophysio - ⚫ Low folate levels are known to increase the risk abnormal cells continue to divide as they produce keratin development of the f etal nervous system. ⚫ Results to nodular, keratinized tumor conf ined to the epidermis ⚫ Exposure to ultraviolet light f rom the sun stimulates the ⚫ Untreated: tumor can invade the dermis and could metastasize production of vitamin D cause death ⚫ Vitamin D promotes the uptake of calcium f rom the small intestine, which is important for the normal development of the 3. Malignant melanoma skeletal system in the f etus and in children. ⚫ Rare f orm, arises f rom melanocytes usually in preexisting moles ⚫ Inadequate quantities of vitamin D can result in rickets, a ⚫ Mole is an aggregation, or “nest,” of melanocytes condition in which the bones are sof t, weak, and easily broken. ⚫ Melanoma - large, f lat, spreading lesion or as a deeply ⚫ Thus, increased skin pigmentation protects against skin cancer pigmented nodule and abnormal development of the nervous system but impairs ⚫ Metastasis: common unless diagnosed & treated early, often skeletal system development. f atal ⚫ The optimal amount of melanin in the skin should be large enough to protect against the harmf ul eff ects of ultraviolet light Skin Cancer Preventive Measure but small enough to allow ultraviolet light to stimulate vitamin D ✓ Limiting exposure to the sun and using sunscreens blocking UV production. ultraviolet light intensity is high in the tropics but light diminishes toward the poles. ✓ UV Types ⚫ Skin color is a genetic adaptation to different exposure to UV ◼ UVA (Longer wavelength & causes most tanning) light ◆ associated with malignant melanoma ◼ Dark-skinned people in the tropics have more melanin ◼ UVB (burning of the skin) ◆ protection against UV light, but still produce vit D ◆ associated with basal cell & squamous cell ◼ Light- skinned people at higher latitudes have less melanin carcinomas ◆ which increases the body’s ability to produce vitamin D while providing adequate ultraviolet light protection. System Pathology of the Integumentary System Burns ⚫ When large areas of skin are severely burned, the resulting PHYSIOLOGY OF systemic ef f ects can be lif e-threatening. INTEGUMENTARY SYSTEM ⚫ Within minutes of a major burn injury, there is increased permeability of capillaries, which are the small blood vessels in which f luid, gases, nutrients, and waste products are normally Integumentary system exchanged between the blood and tissues. ⚫ can be used as a diagnostic aid ⚫ This increased permeability occurs at the burn site and ⚫ observed easily & could ref lects event occurring inside the body throughout the body. As a result, f luid and ions are lost f rom the ◼ Cyanosis: bluish-purple; Jaundice: Yellowish burn wound and into tissue spaces. ⚫ Rashes & Lesions: symptoms of problems in body (Scarlet f ever) ⚫ The loss of fluid decreases blood volume, which decreases the or rashes could possibly indicate reaction to drugs heart’s ability to pump blood. ⚫ Skin: ref lects vitamin A status of body; Def iciency: sandpaper ⚫ The resulting decrease in blood delivery to tissues can cause texture tissue damage, shock, and even death. ⚫ Condition of the nails and hair indicate nutritional status ⚫ Treatment ◼ Nails with iron deficiency = loose normal contour ◼ administering IV f luid at a f aster rate = reverse shock (due to ◼ Hair: reveal toxins /poisonous material in body via toxicity capillary leakage) & prevent death but f luid continues to leak test into tissue spaces, causing edema (swelling) A. B I O 2: ANIMAL PHYSIOLOGY ◼ After 24 hours, capillary permeability returns to normal, amount of IV f luid administered can be decreased ◼ High protein and High calorie diet (injury recovery) ◼ Vit C and Vit K (f or bleeding) ◼ Debridement bef ore skin graf ting thru cleaning of wound bef ore graf ting ⚫ How burns cause capillary permeability to change is not well understood however ◼ It is clear t hat, f ollowing a burn, immunological and metabolic changes occur that aff ect not only capillaries but the rest of the body as well. ◼ chemical mediators which are released in response to the tissue damage, contribute to changes in capillary permeability throughout the body. ◼ Substances releas ed f rom the burn may also play a role in causing cells to f unction abnormally. ◼ Burn injuries result in an almost immediate hypermetabolic state, which persists until wound closure. A. B I O 2: ANIMAL PHYSIOLOGY PHYSIOLOGY OF SKELETAL SYSTEM: long as 10 weeks. But we now know that, if a bone is BONES AND JOINTS immobilized f or as little as 2 weeks, the muscles associated with that bone may lose as much as half their strength. Osteogenesis Imperfecta (Brittle Bone Disease) Furthermore, if a bone is completely immobilized, it is not ⚫ Imperf ect bone f ormation subjected to the normal mechanical stresses that help it f orm ⚫ A rare disorder caused by a number of f aulty genes that results Bone matrix is reabsorbed, and the strength of the bone in either too little collagen f ormation or poor-quality collagen. decreases. In experimental animals, complete immobilization ⚫ As result bone matrix has decreased f lexibility and more easily of the back for 1 month resulted in up to a threef old decrease broken bone in vertebral compression strength. Modern therapy attempts to balance bone immobilization with enough exercise to keep Bone Growth muscle and bone f rom decreasing in size and strength and to ⚫ occurs by the deposition of new bone lamellae onto existing maintain joint mobility. bone or other connective tissue. These goals are accomplished by limiting the amount of time a cast is lef t on the patient and by using “walking casts, ” which ⚫ Appositional Growth allow some stress on the bone and some movement. Total ◼ Osteoblast deposits new bone matrix on the s urf ace of healing of the f racture may require several months. If a bone bones between periosteum and existing bone matrix, heals properly, the healed region can be even stronger than Bone increase in width or diameter. the adjacent bone. ⚫ Growth in the length of a bone, which is the major source of Bones and Homeostasis increased height in an individual, occurs in the epiphyseal ⚫ Bone is the major storage site f or calcium in the body plate. ⚫ movement of Ca in & out of bone helps determine blood Ca ⚫ This type of bone growth occurs through endochondral levels which critical for normal muscle & nervous system ossification. f unction. ⚫ Calcium (Ca2+ ) moves into bone as osteoblasts build new ⚫ Chondrocytes increase in number on the epiphyseal side of bone and out of bone as osteoclasts break down bone. the epiphyseal plate. They line up in columns parallel to the ◼ When osteoblast & osteoclast activity is balanced the long axis of the bone, causing the bone to elongate. Then the movements of calcium into & out of a bone are equal. chondrocytes enlarge and die. ⚫ The cartilage matrix becomes calcified. Much of the Effects of Aging on Skeletal System & Joints cartilage that f orms around the enlarged cells is removed by The most significant age-related changes in the osteoclasts, and the dying chondrocytes are replaced by osteo- blasts. The osteoblasts start f orming bone by skeletal system affect the joints as well as the quality depositing bone lamellae on the surf ace of the calcif ied and quantity of bone matrix. The bone matrix in an cartilage. older bone is more brittle than in a younger bone ⚫ This process produces bone on the diaphyseal side of the because decreased collagen production results in epiphyseal plate. relatively more mineral and less collagen fibers. With aging, the amount of matrix also decreases because Bone Remodelling the rate of matrix formation by osteoblasts becomes involves the removal of existing bone by osteoclasts and the slower than the rate of matrix breakdown by deposition of new bone by osteoblasts. Bone remodeling osteoclasts. occurs in all bone. Remodeling is responsible f or changes in bone shape, the adjustment of bone to stress, bone repair, and Bone mass is at its highest around age 30, and men calcium ion regulation in the body f luids. generally have denser bones than women because of also involved in bone growth when newly formed spongy bone the effects of testosterone and greater body weight. in the epiphyseal plate f orms compact bone. Race and ethnicity also affect bone mass. A long bone increases in length and diameter as new bone is African-Americans and Latinos have higher bone deposited on the outer surf ace and growth occurs at the masses than Caucasians and Asians. After age 35, epiphyseal plate. At the same time, bone is removed f rom the both men and women experience a loss of bone of inner, medullary surf ace of the bone. 0.3–0.5% a year. This loss can increase 10-fold in As the bone diameter increases, the thickness of the compact bone relative to the medullary cavity tends to remain f airly women after menopause, when they can lose bone constant. If the size of the medullary cavity did not also mass at a rate of 3–5% a year for approximately 5–7 increase as bone size increased, the compact bone of the years. diaphysis would become thick and very heavy. A number of changes occur within many joints as a Because bone is the major storage site f or calcium in the body, person ages. bone remodeling is important to maintain blood calcium levels Changes in synovial joints have the greatest effect within normal limits. Calcium is removed f rom bones when and often present major problems for elderly blood calcium levels decrease, and it is deposited when dietary calcium is adequate. This removal and deposition is under people. With use, the cartilage covering articular hormonal control surfaces can wear down. If too much bone is deposited, the bones become thick or Significant loss of bone increases the likelihood of develop abnormal spurs or lumps that can interf ere with normal bone fractures. f unction. Too little bone formation or too much bone removal, For example, loss of trabeculae (thin column and as occurs in osteoporosis, weakens the bones and makes plates of bone-Spongy structure in a cancellous them susceptible to f racture new matrix. bone) greatly increases the risk of fractures of the Subsequently, the spongy bone is slowly remodeled to form vertebrae. compact and spongy bone, and the repair is complete. Although immobilization at a f racture point is critical during the In addition, loss of bone and the resulting fractures early stages of bone healing, complete immobilization is not can cause deformity, loss of height, pain, and good for the bone, the muscles, or the joints. Not long ago, it stiffness. was common practice to immobilize a bone completely for as A. B I O 2: ANIMAL PHYSIOLOGY Loss of bone from the jaws can also lead to tooth 2. Vitamin D from the skin or diet loss. 3. Calcitonin from the thyroid gland. System Pathology of the Condition among Women ✓ PTH and vitamin D is secreted = too low blood Ca levels ✓ Decreased production of the female reproductive ✓ Calcitonin is secreted = too high blood Ca levels hormone estrogen can cause osteoporosis, mostly in ✓ PTH works through 3 simultaneous mechanisms to spongy bone, especially in the vertebrae of the spine and increase blood calcium levels. the bones of the forearm. ✓ Collapse of the vertebrae can cause a decrease in height CASE ON POINT: DISLOCATED SHOULDER or, in more severe cases, kyphosis in the upper back. ⚫ Shoulder joint: most commonly dislocated joint in body. ✓ Estrogen levels decrease as a result of menopause; ◼ Most dislocations result in stretching of joint capsule removal of the ovaries; amenorrhea (lack of menstrual & movement of humeral head to inferior, anterior side cycle) due to extreme exercise or anorexia nervosa (self- of glenoid cavity. starvation); or cigarette smoking. ⚫ Dislocated humeral head is moved back to its normal position by carefully pulling it laterally over inferior lip System Pathology of the Condition among Men of glenoid cavity & then superiorly into glenoid cavity. Reduction in testosterone levels can cause loss of ⚫ Once shoulder joint capsule has been stretched by a bone tissue. shoulder dislocation the shoulder joint may be However, this is less of a problem in men than in predisposed to future dislocations. women because men have denser bones than ⚫ Some indiv have hereditary “loose” joints suseptible to women, and testosterone levels generally don’t experience a dislocated shoulder. decrease significantly until after age 65. Inadequate dietary intake or absorption of calcium, sometimes JOINTS AND MOVEMENTS due to certain medications, can also contribute to osteoporosis. Absorption of calcium from the small intestine decreases with age. Finally, too little exercise or disuse from injury can all cause osteoporosis. Significant amounts of bone are lost after only 8 weeks of immobilization FRACTURES Classification 1. Open (or compound) - if bone protrudes through skin 2. Closed (or simple) - if the skin is not perforated; 3. Complete - totally separates 2 bone fragments 4. Incomplete - if 2 bone is not separated 5. Comminuted (broken into small pieces) - bone breaks into more than 2 fragments. 6. Impacted one of the fragments of one part of the bone is driven into the spongy bone of another fragment Abduction (to take away) is movement away from the median or midsagittal plane. Adduction (to bring together) is movement toward the median plane Moving the legs away from the midline of the body, as in the outward movement of “jumping jacks,” is abduction, and bringing the legs back together is adduction. Pronation and supination are best demonstrated with the elbow flexed at a 90-degree angle. When the elbow is flexed, pronation is rotation of the forearm so that the palm is down, and supination is rotation of the fore- arm so that the palm faces up Eversion is turning the foot so that the plantar When blood calcium levels are too low, osteoclast surface (bottom of the foot) faces laterally activity increases, osteoclasts release calcium from Inversion is turning the foot so that the plantar bone into the blood, and blood calcium levels surface faces medially. increase. Rotation is the turning of a structure around its long When blood calcium levels are too high, osteoclast axis, as in shaking the head “no.” Rotation of the arm activity decreases, osteoblasts remove calcium from can best be demonstrated with the elbow flexed so the blood to produce new bone and blood calcium that rotation is not confused with supination and levels decrease. pronation of the forearm. With the elbow flexed, medial rotation of the arm brings the forearm against Calcium homeostasis is maintained by 3: the anterior surface of the abdomen, and lateral 1. Parathyroid hormone (PTH) from parathyroid glands rotation moves it away from the body. A. B I O 2: ANIMAL PHYSIOLOGY Circumduction occurs at freely movable joints, such as the shoulder. In circumduction, the arm moves so that it traces a cone where the shoulder joint is at the cone’s apex Protraction is a movement in which a structure, such as the mandible, glides anteriorly. In retraction the structure glides posteriorly. Elevation is movement of a structure in a superior direction. Closing the mouth involves elevation of the mandible. Depression is movement of a structure in an inferior direction. Opening the mouth involves depression of the mandible. Excursion is movement of a structure to one side, as in moving the mandible from side to side. Opposition is a movement unique to the thumb and little finger. It occurs when the tips of the thumb and little finger are brought toward each other across the palm of the hand. The thumb can also oppose the other digits. Reposition returns the digits to the anatomical position. Most movements that occur in the course of normal activities are combinations of movements. A complex movement can be described by naming the individual movements involved. Sprain ⚫ results bones of a joint are forcefully pulled apart & ligaments around the joint are pulled or torn. ⚫ separation exists when bones remain apart after injury to a joint. ⚫ dislocation is when the end of one bone is pulled out of the socket in a ball-and-socket, ellipsoid, or pivot joint. Hyperextension ⚫ abnormal, forced extension of a joint beyond its normal range of motion. ⚫ If a person falls & attempts to break the fall by putting out a hand, the force of the fall directed into the hand and wrist may cause hyperextension of the wrist, which may result in sprained joints or broken bones. ⚫ Hyperextension is normal movement of a structure into the space posterior to the anatomical position.