BIOS 256 FINAL EXAM REVIEW PACKET

A&P IV Final Exam Review Packet Ch. 24 DIGESTIVE PROCESSES 1. Ingestion 2. Digestion (mechanical and chemical) 3. Motility (mixing and propulsion) 4. Secretion 5. Absorption 6. Defecation GI TRACT AND ACCESSORY DIGESTIVE STRUCTURES GI TRACT INNERVATION • Autonomic NS o Parasympathetic NV (enhances digestion) o Sympathetic NV (inhibits or slows down digestion) • Enteric Nervous System o Submucosal plexus o Myenteric plexus ENZYMES originating in the oral cavity Salivary glands Parotid glands (under the cheek bones) Submandibular glands (under the mandible) Sublingual glands (under the tongue) • All secrete SALIVA, which contains: o Mostly water o Ions o Buffers o Lysosyme o Salivary amylase Salivary Amylase (made by the salivary glands) - Break down carbohydrates - Converts Polysaccharides to monosaccharides, maltose, maltotriose and alpha-dextrins - Deactivated by stomach acid Lingual Lipase (made by the lingual glands of the tongue) - From lingual glands of the tongue - Break down lipids - Activated by HCl of stomach - Converts triglycerides to fatty acids and monoglycerides THE SIGNIFICANT CELLS OF THE STOMACH AND THEIR SECRETIONS (GASTRIC JUICE) Parietal Cells - Secrete HCl - makes the chyme acidic - kills bacteria - denaturing (unfolding) proteins - activates pepsin along with lingual lipase. - Secrete intrinsic factor, which allows for absorption of vitamin B12 Chief Cells - The major stomach cells - Secrete pepsinogen, which is activated (by stomach acid) and becomes pepsin, a peptidase - Pepsin breaks down proteins - Secrete gastric lipase - breaks down triglycerides into monoglycerides and fatty acids G Cells - Secrete Gastrin (hormone): contracts cardiac sphincter; loosens pyloric sphincter; promotes stomach motility; promotes secretion of pepsinogen from chief cells and HCl from parietal cells Mucous Cells - THEY SECRETE MUCOUS - Mucous forms a protective barrier against acidic chyme THE SIGNIFICANT CELLS OF THE SMALL INTESTINE AND THEIR SECRETIONS Paneth Cells - Secrete lysozome The Enteroendocrine Cells - S Cells - Secrete secretin in response to acidic chyme, promoting release of HCO3- rich pancreatic juice; secondarily, secretin slows down secretion of gastric juice. - K Cells - Secrete GIP (glucose-dependent insulinotropic peptide) - slows down secretion of gastric juice - stimulates insulin secretion - CCK Cells - Secrete cholecystokinin in response to amino acid and fatty acid - CCK stimulates digestive enzyme-rich pancreatic juice - relaxes the sphincter of Oddi - slows gastric emptying - promotes a feeling of satiety - causes contraction of the gallbladder - CCK and Secretin enhance each other Brunner’s Glands - Secrete alkaline rich mucus to counter acidic chyme - Located in the duodenum The Brush-border - Brush-border enzymes are inserted into the plasma membranes of the microvilli in the small intestine Alpha-dextrinase - Alpha-dextrins to glucose Maltase - Maltose to glucose Lactase - Lactose to glucose and galactose Sucrase - Sucrose to glucose and fructose Enterokinase - Converts trypsinogen to trypsin Aminopeptidase - Further breaks down amino acids and peptides Dipeptidase - Dipeptides to amino acids Phosphatases & Nucleosidases - Nucleotides to nitrogenous bases PANCREATIC JUICE Pancreatic Amylase - Breaks down carbohydrates - Converts polysaccharides to a-dextrose, maltose and maltotriose Pancreatic Lipase - Breaks down lipids - Converts triglycerides to fatty acids and monoglycerides Trypsin - Breaks down proteins - Converts proteins to peptides Chymotrypsin - Breaks down proteins - Converts proteins to peptides Carboxypeptidase - Breaks down proteins - Removes amino acid at carboxyl end of peptides Elastase - Breaks down proteins - Converts proteins to peptides Ribonuclease - RNA to nucleotides Deoxyribonuclease - DNA to nucleotides ABSORPTION OF NUTRIENTS - Most absorption (90%) occurs in small intestine, specifically duodenum. - Microvilli have a capillary bed and a lacteal to allow for absorption into the general circulation. The shape and structure of villi and the pliae circulares (circular folds) increase surface area, which allows for more absorption. - Lipids - Lipids need to be emulsified by amphipathic bile salts and then they are surrounded by bile salts in a spherical structure called a micelle. The micelle transports the dietary lipids and other hydrophobic particles in the chyme to the absorptive cells where they enter via simple diffusion - Most of the lipids recombine into larger structures, lipoproteins called chylomicrons. The chylomicrons are too big to diffuse into blood capillaries, thus they are taken up into lacteals. The lacteals merge with larger lymphatic vessels and eventually bring the lipids back into circulation after they empty into the right lymphatic duct. - Amino acids, dipeptides and tripeptides - Brought into general circulation via active transport mechanisms - Carbohydrates - Facilitated diffusion - Fructose - Secondary active transport - Glucose and galactose BILE - MADE by the LIVER - STORED in the GALLBLADDER - Part excretory product, part digestive secretion. - Bile salts are amphipathic and thus play a role in emulsification and absorption of dietary lipids - Cholesterol is a significant component of bile production - Bile can be bound to soluble fiber, increasing its excretion, which then means that the liver has to use more cholesterol… Chemical digestion - See above for digestive enzymes Mechanical digestion Mouth - Mastication breaks down food as the movements of the tongue mix food saliva forming bolus Stomach - Propulsion and retropulsion result in mechanical breakdown of food as it mixes with gastric juice, forming chyme. - Gastric churning (mixing) - Once food particles in the chyme are small enough, propulsion can push some of it through the pyloric sphincter, resulting in gastric emptying. Small intestine - Migrating Motility Complexes - Signaled by dwindling distension after absorption; pushes chyme from duodenum to ileum; peristaltic waves slowly migrate down entire length of small intestine for about 90-120 minutes; chyme stays in small intestine for 3-5 hours - Segmentations - Similar to squeezing the middle and ends of a fluid-filled tube...does NOT move chyme forward along the alimentary canal - mixes chyme and brings it into contact with mucosa for absorption - Caused by distension of an area of the small intestine Large intestine - Haustral churning - In response to distension, haustra contract, squeezing chyme into next haustrum. - Mass peristalsis - Strong peristaltic wave that begins approximately in the middle of the transverse colon and pushes food into the rectum VITAMINS B12 - Essential for RBC production Vitamins A, D, E and K - Carried in micelles along with dietary lipids - Fat-soluble Pantothenic acid - Also known as B5 - Coenzyme needed to synthesize acetyl CoA LIVER (Functions): Synthesis and secretion of bile - The liver’s primary function is to produce and secrete bile, a yellowish, alkaline liquid that consists mostly of bile salts, lecithin, cholesterol and water. - Bile is stored in the gallbladder when it is not needed Carbohydrate metabolism - The liver can store glucose in the form of glycogen (glycogenesis) - The liver can break down glycogen into its constituent glucose (glycogenolysis) - The liver can convert certain amino acids and lactic acid to glucose (gluconeogenisis) Lipid metabolism - Hepatocytes can store some triglycerides, and can break down fatty acids to generate ATP - The liver synthesizes lipoproteins other than chylomicrons which form in the villi of the small intestine - Hepatocytes can synthesize cholesterol and can use cholesterol to make bile Protein metabolism - Hepatocytes can deaminate amino acids so that they can be used for ATP production or converted to carbs or fats; this results in the production of ammonia, which is then converted to urea, which is later excreted in urine. - Hepatocytes synthesize a significant number of important circulating proteins, such as albumin and fibrinogen Processing of drugs and hormones - The liver detoxifies alcohol and can excrete certain drugs into bile. - The liver can alter and excrete thyroid hormones along with the steroid hormones estrogen and aldosterone Excretion of bilirubin - Bilirubin is the main pigmented aspect of bile, derived from the catabolism of heme during RBC recycling. Bilirubin is further metabolized in the small intestine and excreted with feces. Storage - Glycogen - vitamins A, D, E, K and B12 - heavy metals Phagocytosis - The Kuppfer cells of the liver break down aged RBCs, WBCs and some bacteria Activation of vitamin D - Works with skin and kidneys in synthesizing the active form of Vitamin D DEFECATION - Defecation is the elimination of feces from the rectum through the anus - The internal anal sphincter relaxes under involuntary control as the rectum is distended - The external anal sphincter is under voluntary control - Contractions of the diaphragm and abdomen aid in expelling feces Ch. 25 GLYCOLYSIS - Glycolysis is the reduction of the six-carbon molecule glucose (C6H12O6) into the 3-carbon molecule pyruvate (C3H4O6) - This results in a net gain of 2 ATP; 2 are invested, and 4 are generated - Glycolysis occurs in the cytosol - Glycolysis can occur under aerobic or anaerobic conditions - Under aerobic conditions, pyruvate can be decarboxylated to form an acetyl group, which then attaches to coenzyme A to form Acetyl CoA. Acetyl CoA can then enter the Krebs Cycle - Under anaerobic conditions, pyruvate is reduced to lactic acid; this is a reversible action responsible for the concept of the “oxygen debt” - Hydrogen broken off of glucose during these reactions results in the formation of a total of 2 NADH+ - The formation of Acetyl CoA is an intermediate step between glycolysis and the Krebs cycle during which pyruvate is broken down into an acetyl group and fused with coenzyme A. The formation of each acetyl CoA molecule generates 1 NADH+, so by the time we get to the Krebs cycle we have 4 NADH+ KREBS CYCLE - A series of reactions that occurs in the matrix of the mitochondria which further oxidize substrates to liberate hydrogen ions, which are then picked up by the coenzymes NADH and FAD. The reduced coenzymes transport their electrons to a group of other coenzymes along the electron transport chain which consists of a group of various proteins on the inner membrane of the mitochondria which will keep transferring the electrons in a series of exergonic reactions that liberates energy which will eventually be indirectly used to form ATP - The energy released from the transfer of electrons is used to pump H+ against its concentration gradient into the space between the inner and outer mitochondrial membranes--a process called chemiosmosis. H+ then flows back into the matrix, and that flow is used to power up a specialized ATP synthase mechanism, much like the energy inherent in water flowing downstream can be converted into other forms of energy via a water wheel. - For each Acetyl CoA molecule that enters the Krebs cycle, 3 NADH+ and 1 FADH2 are formed; since two Acetyl CoA molecules are formed after glycolysis, for each molecule of glucose, 6 NADH+ and 2 FADH2 are formed ELECTRON TRANSPORT CHAIN • Electron carriers in the mitochondria exergonic reactions release energy used for ATP OVERALL ATP PRODUCTION - Not necessarily a fixed number of ATPs. - We enter the electron transport chain with 10 NADH+ and 2 FADH2 - Glycolysis uses 2 ATP and generates 4, for a net of 2 ATP. - The Krebs cycle ends up making an additional 2 ATP. - For every NADH+ we get on average of 2.5 ATP...so 25 from the 10 NADH+ we generate throughout the previous steps. - For every glucose molecule catabolized, we generally get 30-32 ATP. 4 from steps leading up to the ETC, and 26-28 from the ETC... thus 30-32 ATP KETONE BODIES - During fatty acid catabolism, hepatocytes can take two acetyl CoA molecules and condense them, removing the CoA portion and creating acetoacetic acid - Acetoacetic acid can be converted into beta-hydroxybutyric acid and acetone, both of which diffuse into the bloodstream and can freely diffuse through plasma membranes. - Cells in the brain, heart and kidneys have enzymes that turn beta-hydroxybutyric acid and acetone back into two Acetyl CoA molecules. - If ketone body production outpaces usage, then the acidic ketone bodies must be buffered, which ends up removing alkaline components from the blood, thus increasing pH. If this goes unchecked, it can result in ketoacidosis, which will end up depressing the nervous system, causing first disorientation, then coma, and eventually death. METABOLIC ADAPTATIONS • Absorptive State o Glucose is readily available o Energy input > energy output o Excess nutrients are stored (glycogenesis) o Increases activity of enzymes needed for anabolism o Decreases activity of enzymes needed for catabolism • Post Absorptive State o Low levels of glucose o Energy input < energy output o Stored nutrients must be mobilized o Increases activity of enzymes needed for catabolism o Decreases activity of enzymes needed for anabolism LIPOPROTEINS – TRANSPORT VEHICLES FOR LIPIDS • Chylomicrons • VLDLs • LDLs (BAD!) • HDLs (GOOD!) CH. 26 GROSS ANATOMY OF THE UNRINARY SYSTEM FUNTIONS OF THE URINARY SYSTEM • Regulation o Ionic composition o Blood osmolarity o Blood pH o Blood volume o Blood pressure • Removes waste • Produces hormones o Calcitriol o Erythropoietin HORMONAL REGULATION OF THE URINARY SYSTEM ADH - Anti-diuretic hormone ultimately promotes facultative water reabsorption in the late DCT and collecting duct through the release of aquaporin-II molecules from vesicles within principal cells lining the DCT and collecting duct. These molecules insert into the apical layer of the plasma membrane of principal cells and make them more permeable to water, which flows into the cell and then diffuses out of the basolateral membrane and into the surrounding capillaries. - Secreted in response to increased osmolarity of ECF and decreased blood volume - Ultimately causes you to retain more water Aldosterone - Aldosterone ultimately promotes obligatory water reabsorption stimulating the reabsorption of Na+ and Cl- and the secretion of K+, forming an osmotic gradient that promotes the movement of water from the collecting duct into the principal cells and eventually the blood - The presence of angiotensin II and high K+ concentration in plasma stimulates release of aldosterone Angiotensin II - Secretion of renin is stimulated by low blood volume and pressure, and also by sympathetic innervation. Renin activates the RAA pathway, which ultimately results in the formation of ATII - Decreases GFR by constricting afferent arterioles - Enhances Na+, Cl-, and water reabsorption in the PCT by enhancing the work of Na+-H+ antiporters, which swap Na+ in the tubules for H+. This occurs at the apical membrane. Atrial Natriuretic Peptide - Secreted in response to stretching of atria, signaling high blood volume and pressure. - Relaxes mesangial cells, effectively increasing surface area of glomerular capillaries, thus increasing GFR. - Simultaneously inhibits the reabsorption of Na+ and water in PCT - Also inhibits secretion of ADH and aldosterone PTH - Regulates Ca+ reabsorption later in the nephron AUTOREGULATION OF GFR Myogenic Mechanism - Simple but effective mechanism; walls of afferent arteriole are sensitive to various levels of stretching. - Then distended, they will contract to normalize GFR - When flow is weak, they will dilate to increase GFR to normal levels - Normalizes GFR within seconds in response to change in BP Tubuloglomerular Feedback - Macula densa cells, where the DCT meets the afferent arteriole, are sensitive to increased levels of NaCl- and H20, indicative of high GFR (not enough time to reabsorb solutes and water) - In response, they inhibit the release of NO (a vasodilator), thus causing walls of the afferent arteriole to contract and decrease GFR. - Opposite series of events occurs with low presence of NaCl- and H20 NEURAL REGULATION OF GFR - Sympathetic innervation causes both afferent and efferent arteriole to constrict, slightly lowering GFR - Increasing levels of sympathetic innervation cause constriction in the afferent arteriole to predominate, lowering GFR more noticeably. - This reduces urine output and allows blood to flow to other tissues Pressures and GFR - There are four pressures which affect the rate at which plasma is filtered through the glomerulus - Glomerular blood hydrostatic pressure (GBHP) promotes filtration and is directly related to blood pressure, thus is sensitive to the mechanisms which control BP. Typically 55mmhg - Blood colloid osmotic pressure (BCOP) opposes filtration; pulling force exerted by proteins suspended in plasma, predominantly albumin. Typically 30mmhg - Capsular hydrostatic pressure (CHP) is the filtration-opposing force exerted by fluid in the capsular space. Typically 10mmhg - There is technically a capsular osmotic pressure, but under normal physiological conditions it is 0mmhg due to the fact that the filtration membrane inhibits the filtration of large proteins. - GFR = GBHP - BCOP - CHP = 15mmhg - Even small changes to this pressure can be disruptive to homeostasis NORMAL URINE - pH varies considerably with diet, ranges between 4.0 and 8.0 - Normal color is yellow or amber; affected by diet, concentration etc. PATH OF BLOOD THROUGH KIDNEYS - Renal artery - Segmental arteries - Interlobar arteries - Arcuate arteries - Cortical radiate arteries - Afferent arteriole - Glomerulus - Efferent arteriole - Peritubular capillaries/vasa recta - Cortical radiate vein - Arcuate vein - Interlobar vein - Renal vein THE NEPHRON - The nephron is the functional unit of the kidneys! It can be further subdivided, in order, into… - The Renal Corpuscle - Bowman’s capsule + Glomerulus - Filtration - The Proximal Convoluted Tubule - Reabsorbs approximately 70% of fluid (water), solutes, and various important ions - The Loop of Henle - Consists of a thin descending limb and a thick descending limb, which will be discussed individually and in detail below… - Cortical nephrons have a short Loop of Henle and are more numerous - Juxtamedullary nephrons have a much longer Loop of Henle that extends deep into the medulla - Descending limb of Loop of Henle - Impermeable to solutes - Permeable to water - Osmolarity thus increases as we descend the Loop of Henle, all the way up to about 1200 mOsm/liter at the actual loop, since water is being reabsorbed (obligatory reabsorption!) due to the salty interstitial fluid - Why is the interstitial fluid so salty? - I’m glad you asked... - Ascending limb of Loop of Henle - The salty guy - In its thickest part there are symporters which actively pump Na+-K+-2Cl- into the surrounding interstitial fluid – so, this is where the solutes are reabsorbed - Why? - Well, the ascending limb is essentially impermeable to water, so osmolarity within the tubule goes all the way down to about 150 mOsm/Liter by the time we reach the distal convoluted tubule - Still why? - Well, this is what we call a COUNTERCURRENT MULTIPLIER; we’re using this mechanism to concentrate the urine without spending excess energy. By using energy only in the thick, ascending limb to pump out Na+-K+-2Cl-, we establish an osmotic gradient between the two limbs that naturally pulls water out of the tubules in the water-permeable descending limb. - What really eventually decides whether the urine is concentrated or dilute is the presence of ADH, which exerts its effects predominantly on our celebrity guest star, the collecting duct. As you know, ADH promotes facultative water reabsorption, which makes the urine more and more concentrated because water is leaving but solutes are remaining. - The Early Distal Convoluted Tubule - Reabsorbs about 10-15% of filtered water, and 5% of filtered Na+ & Cl- - Sensitive to parathyroid hormone, which promotes reabsorption of Ca2+ - Late Distal Convoluted Tubule (Sensitive to hormonal regulation) - Solute and water reabsorption depend on body’s needs, moderated by aldosterone and ADH - Major site of K+ secretion - Principal cells reabsorb water when ADH presence is high - Intercalated cells reabsorb K+ and HCO3- and secrete H+ - Guest Starring: The Collecting Duct, Who is Not Actually a Part of The Nephron - ADH (facultative reabsorption; decreases interstitial fluid osmolarity, increases blood volume and pressure) - Aldosterone (obligatory reabsorption; increases interstitial fluid osmolarity, blood volume and pressure) 12 Micturition - To urinate Detrusor Muscle - Smooth muscle in the wall of the urinary bladder, which involuntarily contracts when distended Internal urethral sphincter - Relaxes during micturition reflex External urethral sphincter - Inhibited during the micturition reflex so you don’t pee on yourself Urinary bladder - Stores your urine Ureter - Transports urine from kidneys to urinary bladder Urethra - Passageway for discharging urine out of the body Aging and the kidneys - Less blood flow to kidneys during older age leads to reduced size and functionality of kidneys. Ch. 27 Fluid Compartments and Fluid Homeostasis Water gain and loss - Water is gained through ingestion predominantly and metabolic synthesis when electrons are accepted by oxygen during aerobic cellular respiration - Water is lost predominantly through the kidneys (urine), through the skin as sweat and insensible perspiration, through exhalation by the lungs, and in small quantities excreted in feces. - Water gain and water loss are typically at equilibrium. Hormonal regulation is compensatory. - The thirst center is in the hypothalamus, which is sensitive to changes in plasma osmolarity. Dehydration stimulates thirst. - SEE FIGURES BELOW: HORMONAL REGULATION OF H20 BALANCE AND IONS BECAUSE IT’S NOT SENSIBLE TO SEPARATE THESE SUBJECTS SINCE THEY ARE INTIMATELY RELATED - Atrial Naturetic Peptide - Released when the atria are stretched due to increased blood volume - Inhibits reabsorption of Na+ and water in PCT and collecting duct - Suppresses secretion of ADH and aldosterone - Promotes natriuresis (more Na+ in the urine) and diuresis (more urine output), decreasing blood volume and blood pressure - Antidiuretic Hormone - ADH is a posterior pituitary hormone; secretion is stimulated by increased plasma osmolarity. - ADH increases facultative water reabsorption by increasing the permeability of principal cells in the late DCT and the collecting duct. - Specifically, it promotes the insertion of aquaporin-2 channel proteins into the apical membranes of the principal cells. - Helps you retain water - Renin-Angiotensin-Aldosterone System - Angiotensin II and aldosterone go hand in hand, working in tandem. - When blood volume and blood pressure DECREASE, the walls of the afferent arterioles (remember, they are the vessels which branch into the glomeruli) are stretched less, causing juxtaglomerular cells to secrete renin. - Renin derives angiotensin I from angiotensinogen; once angiotensin I reaches the lungs, angiotensin-converting enzyme converts it into angiotensin II (ATII) - ATII causes vasoconstriction of the afferent arterioles - ATII enhances reabsorption of Na+ & Cl- (thus water!) in the PCT by stimulating Na+/H+ antiporters; - This also stimulates the adrenal cortex to release aldosterone, which itself causes the principal cells of the DCT and collecting duct to reabsorb more Na+/Cl-, and to secrete more K+. This causes obligatory water reabsorption since water follows the newly established osmotic gradient! - Helps you retain water ELECTROLYTES IN BODY FLUIDS ION DISTRIBUTION IN THE BODY: Sodium - Na+ is the main cation in ECF - Responsible for maintenance of the electrical gradient - Accounts for about 50% of the osmolarity of ECF - Levels controlled by ADH, aldosterone and ANP Chloride - Most abundant anion in ECF - Functions in chloride shift mechanisms via HCO3-/Cl- antiporters - Is reabsorbed and moves with Na+ via Na+/Cl- symporters - Combines with H+ to form HCl via parietal cell secretions Potassium - Most prevalent cation in ICF - Responsible for maintaining cell’s resting membrane potential and repolarizing cell’s membrane after conduction of an action potential - Aldosterone stimulates principal cells to secrete more K+ Bicarbonate - Functions as a buffer - Second most prevalent anion in ECF, but also seen in ICF - Blood level of HCO3- is regulated by intercalated cells of the kindeys Calcium - Most abundant mineral in the body, as it is stored in our bones - Combines with phosphates to form the crystalized matrices of our bones - Mainly in ECF otherwise...functions in the plateau phase of cardiac action potentials; can be used in second messenger systems to stimulate release of molecules stored in vesicles; binds to troponin to make myosin bonding sites accessible Phosphate - Exists either combined with calcium as the structural component of bones or ionized in intracellular fluid - Phosphate ions function as buffers (described in a previous section) Magnesium - 54% found as magnesium salts in bone matrix - Second most common intracellular cation - Used as a coenzyme ELECTROLYTE IMBALANCES IN THE BODY: BUFFER SYSTEMS: Protein Buffer System - Proteins by nature have an amino group (NH2) and a carboxyl group (COOH) - These represent the reactive components of the proteins, which allow proton acceptance and proton donation. - The carboxyl group can donate H+ when pH rises: - - The amino group can accept H+ when pH drops: - Hemoglobin also acts a significant buffer: - Carbonic Acid Bicarbonate Buffer system - CO2 + H20 <-> H2CO3 <-> HCO3- + H+ - HCO3- functions as a weak base - H2CO3 functions as a weak acid - If the blood becomes acidic (high proton concentration), the reactions trend toward the production of H2CO3 from HCO3- + H+, then the dissociation of carbonic acid into H20 and CO2. The H20 serves many functions, and the CO2 is exhaled. - If the blood is alkaline (low proton concentration), H20 and CO2 combine to form H2CO3, which then dissociates into HCO3- and H+, thus donating protons and lowering pH. - Understanding this depends on understanding the concept of mass action equilibrium… Phosphate Buffer System - Functions similarly to the carbonic acid bicarbonate buffer system! - Phosphates are major anions in ICF, minor in ECF - Dihydrogen phosphate (H2PO4) can buffer strong bases by turning them into weak ones ex: OH- + H2PO4 → H20 + HPO 2−¿ 4¿ - Monohydrogen phosphate ( HPO 2−¿ 4¿ ) can buffer acids by accepting protons ex: H+ + HPO 2−¿ 4¿ → H2PO 2−¿ 4¿ Exhalation of Carbon Dioxide - See previous explanation - CO2 (Carbon dioxide) + H2O (Water) ⇌ H2CO3 (Carbonic acid) ⇌ H+ (Hydrogen ions) + HCO3- (Bicarbonate ions) Renal Secretion of H+ and Reabsorption of HCO3- - Secretion of H+ in urine is major buffer system - In the PCT Na+/H+ antiporters reabsorb Na+ as they secrete H+ - More important are the intercalated cells of the collecting duct! There are both intercalated A and B cells, but the book doesn’t really distinguish, so… - Intercalated A cells have proton pumps in their APICAL membranes, which can spit out H+ against its concentration gradient, making urine highly acidic, up to 1000x more acidic than blood! - As H2CO3 dissociates within the intercalated A cells, the protons are pumped out into the tubules and the bicarbonate is swapped for Cl- in the basolateral membrane, thus reabsorbing HCO3-. So... intercalated cells SECRETE H+ & REABSORB HCO3- - Intercalated B cells have the opposite membrane protein positioning--proton pumps in the basolateral membrane and HCO3-/Cl- antiporters in the apical membrane...so they secrete bicarb and reabsorb H+ - H+ in the collecting duct combines with NH3, forming NH4+ and also with HPO 2−¿ 4¿ to form H2PO 2−¿ 4¿ . Buffering H+ in the urine is not that important, since we’re just going to excrete it SUMMARY TABLE BELOW: ACID BASE BALANCE: ACIDOSIS AND ALKALOSIS - Acidosis is a condition that results when blood pH drops below 7.35 - This leads to depression of the central nervous system, coma, and eventually death - The response to acidosis or alkalosis is compensation. The compensatory mechanisms are respiratory and renal. Essentially, if the respiratory system is the cause of acidosis, the renal system has to compensate, and if the cause is metabolic, the respiratory system has to compensate. - Respiratory compensation is accomplished by hyperventilation and hypoventilation (think CO2) - Renal compensation is accomplished by the aforementioned functions of the intercalated A and B cells pumping out H+ and exchanging HCO3- for Cl- Respiratory Acidosis - Caused by abnormally high levels of CO2 in systemic blood due to any sort of obstruction or other physiological condition (such as hypoventilation) which would interfere with the exhalation of CO2 - Can be countered by the functions of the kidneys, secreting more H+ and reabsorbing more HCO3-, but only to a certain degree - Typically, treatments focus on ventilation therapy Respiratory Alkalosis - Caused by low blood CO2 levels, resulting from such things as hyperventilation, or oxygen deficient atmospheric conditions - Kidneys can compensate, again, to a certain degree - Treatment focuses on restoring blood CO2 levels--this is where we get the classic “anxious guy breathing into a paper bag.” The paper bag traps exhaled CO2, allowing the patient to then inhale it back. Metabolic Acidosis - Results from low blood HCO3- levels - Things that can cause metabolic acidosis include loss of bicarbonate through diarrhea or renal dysfunction; renal failure resulting in the kidneys not being able to adequately reabsorb bicarbonate; the accumulation of acids other than carbonic acid, like in ketoacidosis - Respiratory compensation would come in the form of hyperventilation Metabolic Alkalosis - Caused by high blood HCO3- concentration - Is often the result of excessive vomiting, which leads to the loss of large amounts of HCl- - Respiratory compensation would come in the form of hypoventilation SUMMARY BLEOW: Ch. 28 MALE REPRODUCTIVE SYSTEM: WITH ACCESSORY GLANDS SHOWN: CELLS OF THE MALE GONADS (REMEMBER…MALE GONADS ARE THE TESTES) LEYDIG CELLS: • Interstitial cells • Secrete testosterone SERTOLI CELLS (ALSO KNOWN AS NURSE CELLS) • Epithelial cells of the semineferous tubules • Support sperm production SPERMATOGENESIS - Spermatogenesis is the process by which spermatozoa are formed in the seminiferous tubules from diploid parent cells called spermatogonia - The seminiferous tubules consist of various spermatogenic cells and the supportive sustentacular (Sertoli) cells - Sertoli cells perform various functions, including forming the blood-testis barrier; nourishing developing spermatogenic cells and controlling their movements; secrete inhibin and regulate the effects of FSH and testosterone; releasing sperm into the lumen of the seminiferous tubule - Order of development: One Spermatogonia (2n) → One Primary Spermatocytes (2n) → Two Secondary Spermatocytes (n; product of meiosis I) → Four Spermatids (n; basically, sperm that have yet to undergo spermiogenesis; product of meiosis II) More straightforward, less anatomical picture on next page... - Spermiogenesis is the process by which spermatids become functional spermatozoa - Acrosome (head sheath) develops - Flagella (motile, tail-like cytoskeletal extension) - Mitochondria multiply (the sperm will need lots of energy in order to move) - Spermiation refers to the process by which sperm are released from their connections to Sertoli cells into the lumen of the seminiferous tubules Hormonal control of spermatogenesis - At puberty, GnRH induces the release of FSH and LH from the anterior pituitary - LH signals interstitial (Leydig) cells to start secreting testosterone, the masculinizing hormone - FSH and testosterone stimulate Sertoli cells to begin secreting androgen-binding protein (ABP); ABP binds to testosterone, keeping its concentration high - Together, FSH and testosterone induce spermatogenesis - SEE FIGURES ON THE FOLLOWING PAGE PATHWAY OF SPERM - Seminiferous tubules → Straight tubules → Rete testis → Efferent ducts → Epididymis →Vas Deferens SPERM MOVEMENT - Motility is achieved by using ATP to generate energy in order to “whip” the flagella around, propelling the sperm forward - Contractions of the myometrium help “suck” sperm toward the uterine tubes ACCESSORY SEX GLANDS AND THEIR SECRETIONS - Seminal Vesicles - Secrete majority (approximately 60-70%) of the fluid that constitutes semen - Secrete alkaline fluid containing prostaglandins (enhance sperm motility), fructose (source of energy for sperm), and clotting proteins - Prostate Gland - Contributes another 25% of semen - Secretion includes citric acid (energy source); proteolytic enzymes (break down clotting proteins in seminal vesicle secretions); acid phosphatase; and seminalplasm, which is antibacterial - Bulbourethral Glands - Mucous type secretions for lubricating the glans penis - Helps facilitate sexual intercourse FEMALE REPRODUCTIVE SYSTEM: (FEMALE REPRODUCTIVE TRACT IS MADE OF INTERCONNECTED CAVITIES) CLOSER LOOK AT THE UTERINE TUBES: EXTERNAL GENITALIA – COLLECTIVELY KNOWN AS THE VULVA: FEMALE GONADS - OVARIES: ▪ Functions ▪ Production of immature female gametes (oocytes) ▪ Secretion of female sex hormones (estrogens, progestins) ▪ Secretion of inhibin, which is involved in feedback control of pituitary secretion of FSH OOGENISIS: ▪ Begins in the first three months of embryonic life ▪ Oogonia (diploid) undergo mitosis to yield 2-4 million clones from which all ova are derived ▪ Oogonia differentiate into primary oocytes ▪ Primary oocytes begin meiosis I and replicate their DNA ▪ At this point, meiosis stops and primary oocytes enter a state of suspended development called meiotic arrest ▪ Primary oocytes remain in meiotic arrest until just before ovulation ▪ Thus, at birth, a female’s eggs are in the form of primary oocytes in meiotic arrest: ▪ 46 chromosomes that have two sister chromatids a piece (2n x 2) ▪ When female reaches puberty, one primary oocyte per month continues to meiosis I ▪ Just prior to ovulation, a primary oocyte completes meiosis I to yield two daughter cells possessing 23 replicated chromosomes each (n x 2) ▪ One daughter cell = secondary oocyte ▪ The other daughter cell = first polar body ▪ Secondary oocyte receives most of the cytoplasm during cell division and continues to develop further ▪ First polar body degenerates and dies ▪ Meiosis II ONLY occurs if the secondary oocyte is fertilized ▪ If fertilization occurs, meiosis II yields ▪ One ovum (which receives most of the cytoplasm) ▪ One second polar body (which degenerates and dies) ▪ Thus, a fertilized ovum will contain 23 single chromosomes (inherited from the secondary oocyte) ▪ Plus 23 chromosomes inherited from the sperm ▪ End result = a fertilized ovum has a total of 46 chromosomes (2n) HORMONAL REGULATION OF FEMALE REPRODUCTIVE SYSTEM: OVERALL SUMMARY OF HORMONES AND BOTH REPRODUCTIVE CYCLES: LACTATION - Lactation refers to the production, secretion and ejection of milk from them the nipples, a process associated with pregnancy and childbirth - Production - Production of milk is carried out by the mammary glands - Each mammary gland is further divided into 15-20 lobes separated by adipose tissue - Within each lobe are smaller lobules containing the actual glands which produce the milk--the alveoli - Ejection - Milk produced in the alveoli moves through the secondary tubules and into the mammary ducts, then from there it enters the lactiferous sinuses, then the lactiferous ducts - Each lobe is typically served by a single lactiferous duct, which eventually carries the milk to the surface - Hormonal control - Milk production is stimulated by prolactin - Milk ejection is stimulated by oxytocin (suckling induces oxytocin release - Benefits of breastfeeding - Beneficial Cells: Gives the baby important white blood cells, such as neutrophils, macrophages, plasma cells, and T lymphocytes - Beneficial Molecules: Transfers IgA antibodies, which typically afford the baby protection from harmful microbes in the environments it shares with its mother - Small reduction in incidence of diseases later in life, attributed to aforementioned immunity “headstart” - Supports optimal growth; enhances neurological development; establishes mother-infant relationships; ready and adequate form of nutrition that is sterile and designed for a baby’s digestive system - Prolactin (the milk-producing hormone) levels increase as pregnancy progresses, but the presence of progesterone inhibits the effects of prolactin - After delivery, estrogens and progesterone levels decrease, meaning prolactin becomes more effective - Suckling sends nerve impulses from stretch receptors in the nipple to the hypothalamus, maintaining prolactin secretion - Oxytocin releases milk into the mammary ducts via the milk ejection reflex - Milk formed by alveoli is stored until the baby begins suckling, at which point nerve impulses work on the posterior hypothalamus to induce oxytocin secretion - Oxytocin works on myoepithelial cells that surround the glands and ducts, moving milk from alveoli into the mammary ducts where it can be sucked out by the infant - Oxytocin also inhibits the release of prolactin-inhibiting hormone, thus increasing prolactin levels and milk production - This is another example of positive feedback Anatomy of the breasts HOMOLOGOUS STRUCTURES METHODS OF BIRTH CONTROL - Tubal ligation - Cutting and tying of the uterine tubes - Vasectomy - Surgical incision and subsequent tying of each vas deferens, meaning sperm have no way to move into the urethra for ejaculation - Hormonal birth control - Contain estrogens, which inhibit release of FSH, meaning a dominant follicle does not develop - Contain progesterone, which inhibits release of LH, meaning ovulation does not occur - Spermicide - Kill sperm - Barrier methods - Condoms etc. - Abstinence - Just don’t do it!!! - Intrauterine Devices (IUDs) - Block sperm from entering uterine tubes Ch. 29 TRIMESTERS - First trimester - First three months - Most critical period - Organogenesis - Highest level of vulnerability to teratogens - Second trimester - Months 4-6 - Organs continue to develop, but no new major organs are formed - Fetus looks distinctly human by the end of this stage - Third trimester - Last three month - Rapid fetal growth - Organ systems becoming fully functional FERTILIZATION - Sperm that reach the secondary oocyte undergo capacitation, as their tails prepare to beat more vigorously and various secretions from the female reproductive tract break down the sperms’ acrosomes, revealing the enzymes underneath - The sperm use the movement of their flagella along with the exposed acrosomal enzymes in order to penetrate the corona radiata and make their way toward the zona pellucida, where they bind onto ZP3 receptors. Many sperm will bind to ZP3 receptors, triggering the release of acrosomal enzymes which eat through the zona pellucida, allowing the sperm to move toward the oocyte’s plasma membrane - The first sperm to fuse with the oocyte’s plasma membrane triggers depolarization, stopping other sperm from being able to fuse with the oocyte’s membrane--a process called fast-block to polyspermy - At the same time, the depolarization triggers the release of calcium ions which then stimulate vesicles within the oocyte to undergo exocytosis; the molecules in the vesicles deactivate ZP3 and cause the zona pellucida to harden significantly--a process called slow-block to polyspermy - The secondary oocyte completes meiosis II, forming a large, functional ovum containing the female pronucleus and a second polar body as the sperm’s nucleus forms into the male pronucleus - The two pronuclei merge into a single nucleus with the diploid number of chromosomes, forming a zygote - The zygote undergoes successive series of cleavages until it forms a mass of cells about the same size as the original zygote called the morula - Toward day four or five the growing morula enters the uterine cavity where it receives nutrient-rich secretions from the endometrium called uterine milk. Once the morula is 32-cells large, the uterine milk forms a cavity within the mass of cells called the blastocyst cavity. At this time, the morula becomes the blastocyst. - At this point two distinct cell populations arise: the outer trophoblast and the inner embryoblast. The trophoblast will become the outer chorionic layer which forms the fetal portion of the placenta. The embryoblast, as you might have guessed, eventually becomes the embryo and gives rise to the three germinal layers from which all our tissues and organs are derived. - Once the blastocyst sheds the zona pellucida, I would consider fertilization to be over, signaling us to move on to implantation IMPLANTATION - Implantation occurs during the secretory phase of the uterine cycle, about a week after ovulation when the progesterone from the corpus luteum is stimulating the endometrium. Implantation is simply the blastocyst, oriented with the embryoblast facing forward, attaches to the endometrium and begins to burrow in. Once implantation has occurred, we call the more vascularized endometrium the decidua basalis. FIRTILIZATION AND IMPLANTATION FIRST WEEK OF DEVELOPMENT SECOND WEEK OF DEVELOPMENT 9 DAYS AFTER FERTILIZATION 12 DAYS AFTER FERTILIZATION ● Epithelial lining of ● All skeletal and cardiac ● All nervous tissue. gastrointestinal tract (except oral cavity and anal canal) and epithelium of its glands. muscle tissue and most smooth muscle tissue. ● Cartilage, bone, and other connective tissues. ● Epidermis of skin. ● Hair follicles, arrector pili muscles, nails, epithelium of skin ● Epithelial lining of urinary ● Blood, red bone marrow, glands (sebaceous bladder, gallbladder, and liver. and lymphatic tissue. ● Blood vessels and and sudoriferous), and mammary glands. ● Epithelial lining of pharynx, lymphatic vessels. ● Lens, cornea, and auditory (eustachian) tubes, tonsils, tympanic (middle ear) cavity, larynx, trachea, bronchi, and lungs. ● Dermis of skin. ● Fibrous tunic and vascular tunic of eye. ● Mesothelium of thoracic, internal eye muscles. ● Internal and external ear. ● Neuroepithelium of ● Epithelium of thyroid gland, abdominal, and pelvic sense organs. parathyroid glands, pancreas, and thymus. cavities. ● Kidneys and ureters. ● Epithelium of oral cavity, nasal cavity, ● Epithelial lining of prostate ● Adrenal cortex. paranasal sinuses, and bulbourethral (Cowper’s) glands, vagina, vestibule, urethra, and associated glands such as greater (Bartholin’s) vestibular glands and lesser vestibular glands. ● Gonads and genital ducts (except germ cells). ● Dura mater. salivary glands, and anal canal. ● Epithelium of pineal gland, pituitary gland, and adrenal medullae. ● Melanocytes (pigment cells). ● Gametes (sperm and ● Almost all skeletal oocytes). and connective tissue components of head. ● Arachnoid mater and pia mater. HORMONAL REGULATION OF PREGNANCY LABOR (PARTURITION) - Labor is hormonally induced and regulated - Toward the end of gestation there is a surge of estrogens because the placenta increases its secretion of corticotropin-releasing hormone, which stimulates the fetal pituitary gland to secrete adrenocorticotropic hormone (ACTH). ACTH then works on the fetal adrenal glands to secrete cortisol and dehydroepiandrosterone (DHEA). DHEA is converted into an estrogen by the placenta. - High estrogen levels increases the number of oxytocin receptors on uterine muscle fibers, and stimulates uterine muscle fibers to form gap junctions with one another - Oxytocin from the posterior pituitary stimulates the uterus to contract as relaxin from the placenta widens the pubic symphysis, relaxes the sacroiliac and sacrococcygeal joints, and dilates the cervix. - Estrogen also stimulates the placenta to release prostaglandins, which in turn stimluate the production of enzymes which digest collagen fibers in the uterus, softening it - Contractions are controlled by positive feedback - As the head of the baby moves toward the cervix, the cervix becomes dilated - As the cervix is stretched, it sends signals the neurosecretory cells of the hypothalamus, which respond by secreting more oxytocin - Increased levels of oxytocin strengthen contractions, which pushes the baby more, which distends the cervix more, which causes more oxytocin to be released - This continues until birth, which breaks the cycle and removes the pressure on the cervix - Uterine contractions are peristaltic, starting at the top of the uterus and moving toward the cervix - Stages of true labor - True labor is signaled by contractions occurring at regular intervals, pain in the back intensified by walking, and discharge of bloody mucus - Stage of dilation - Onset of labor to complete dilation of cervix - Lasts 6-12 hours - Regular contractions - Rupturing of amniotic sac and complete dilation of cervix (10cm) - Stage of expulsion - Time from complete cervical dilation to actual delivery - Lasts from 10 minutes to several hours - Placental stage - 5-30 minutes after delivery until the placenta is expelled - Puerperium - Return to prepregnancy state - Involution: return of uterus to original size - Lochia: discharge consisting of blood and serous fluid derived from site of placenta CHROMOSOMES AND GENETICS - Chromosomes represent DNA in its condensed form, ready for cell division. When the cell is not dividing, the DNA is loosely organized in a form called chromatin. - Each chromosome is formed by two identical strands of DNA called chromatids which are joined at their center by a structural protein called the centromere. This is why we can pull apart the sister chromatids during mitotic division and end up with identical daughter cells. - Individual segments of the condensed DNA strands are called genes, and they are templates for the production of various proteins which in total affect all aspects of our being. - Now that we understand what a gene is, we can understand what an allele is! So, we have 22 pairs of autosomes, plus the pair of sex chromosomes which determine our sex. One chromosome from each pair is inherited from the mother, and the other from the father. These homologous chromosomes have genes which code for the same trait, and these genes are called alleles. - An allele that dominates or masks another allele is said to be a dominant allele, which expresses the dominant trait - The masked allele is thus the recessive allele, which expresses the recessive trait - In punnett squares, where capital letters express dominant alleles, and lowercase letters represent the recessive ones. And genotype simply refers to the combination of genes one has... - Now, if one has two dominant alleles or two recessive alleles, then we consider them to have a homozygous genotype (i.e. AA or aa). - If they have one of each kind of allele, then we consider them to be heterozygous (i.e. Aa) - Phenotype is the physical expression of a genetic combination. - Incomplete dominance: Neither allele masks the other entirely, such as is the case in sickle-cell anemia - Multiple-allele inheritance: Results from genes that have more than two forms, such as the ABO blood group - Co-dominance: Both genes are expressed equally, such as having the AB bloodtype. - Polygenic inheritance: Most of the traits we inherit are the product of combined effects of two or more genes. - Complex inheritance: Traits are the product of many genes plus environmental factors - Karyotype: Entire set of chromosomes arranged by size and centromere position - Autosomes: The 22 pairs of homologous chromosomes that do not determine sex - Sex chromosomes: The 23rd pair of chromosomes that determine sex. XX is female; XY is male. The Y chromosome is much smaller… - Sex-linked inheritance: Well, the sex chromosomes also have genes which are responsible for passing along several nonsexual traits. Typically, since the X chromosome is much larger, these traits are linked to the X chromosome - Autosomal dominant: abnormal gene is carried on the dominant allele; “normal” can only be homozygous recessive