BIOH 370 1st Edition Final Exam Study Guide Lectures: 26 - 37Lecture 26 (April 10) Urinary System Day 1List and describe the Urinary System functions- Consists of the kidneys, ureters, bladder, and urethra- Maintains homeostasis by managing the volume and composition of fluid reservoirs, primarily blood- Regulation of blood ionic composition: Na+, K+, Cl–- Regulation of blood pH: H+, HCO3–- Regulation of blood volume: H20- Regulation of blood pressure- Maintenance of blood osmolarity- Production of hormones: Calcitrol and Erythropoietin- Regulation of blood glucose level- Excretion of metabolic wastes and foreign substances (drugs or toxins)Where are the kidneys located? Describe the blood and nerve supply to the kidneys.- Kidneys are retroperitoneal, partly protected by the lower ribs- Renal arteries deliver ~ 1/4 (1200 ml) of cardiac output to the kidneys each minute- Arterial flow into and venous flow out of the kidneys follow similar paths- Nerve supply is via sympathetic fibers from the renal plexusWhat is a nephron and what does it do? What are the two main parts? What are the types of cells that make up each part of the nephron?- Structural and functional units that form urine- ~1 million per kidney- Two main parts1. Glomerulus : a tuft of capillaries 2. Renal tubule: begins as cup-shaped glomerular (Bowman’s) capsule surrounding the glomerulusThe kidneys filter the body’s entire plasma volume 60 times each day• Glomerular filtration, • tubular reabsorption • tubular secretion• Filtrate• Blood plasma minus proteins• Urine• <1% of total filtrate• Contains metabolic wastes and unneeded substancesDescribe the structure/function of a renal corpuscle:- The glomerular endothelial cells have large pores (fenestrations) and are leaky.- Basal lamina lies between endothelium and podocytes.- Podocytes form pedicels, between which are filtration slits.II. Glomerular Filtration• • Driven by blood pressure- Opposed by capsular hydrostatic pressure and blood colloid osmotic pressure- Water and small molecules move out of the glomerulus.- In one day, 150–180 liters of water pass out into the glomerular capsule.- Glomerular filtration rate – amount of filtrate formed by both kidneys each minute- Homeostasis requires kidneys to maintain a relatively constant GFR- Too high – substances pass too quickly and are not reabsorbed- Too low – nearly all reabsorbed and some waste products not adequately excretedElaborate on the Juxtaglomerular Apparatus (JGA): senses NaCl and Blood Pressure- Granular cells (juxtaglomerular, or JG cells)1. Enlarged, smooth muscle cells of arteriole2. Secretory granules contain renin3. Act as mechanoreceptors that sense blood pressure- Macula densa1. Tall, closely packed cells of the ascending limb2. Act as chemoreceptors that sense NaCl content of filtrate- Extraglomerular mesangial cells 1. Interconnected with gap junctions2. May pass signals between macula densa and granular cells- Glomerular filtration rate – amount of filtrate formed by both kidneys each minute1. Homeostasis requires kidneys to maintain a relatively constant GFRa. Too high – substances pass too quickly and are not reabsorbedb. Too low – nearly all reabsorbed and some waste products not adequately excreted- GFR averages 125mL/min in males and 105mL/min in females- Controlled by:Renal AutoregulationNeural RegulationHormonal RegulationDesecribe the renal autoregulation- Myogenic Mechanism- Smooth muscle cells in afferent arterioles contract in response to elevated blood pressure- Tubuloglomerular Feedback1. High GFR diminishes reabsorption2. Macula Densa inhibits release of nitric oxide3. Afferent arterioles constrict - Substances that are filtered reabsorbed and excreted in urine dailyIII. Renal Tubule:- The filtrate passes from the glomerular capsule to the renal tubule1. Proximal Convoluted Tubule2. Nephron Loop Descending Loop Ascending Loop3. Distal Convoluted TubuleLecture 27 (April 13) Urinary System Day 2 Compare and contrast the difference between the cortical and juxtamedullary nephrons.a. Cortical Nephrons: 80-85% of nephrons- Renal corpuscle in outer portion of cortex- Short loops of Henle extend only into outer region of medulla- Create urine with osmolarity similar to bloodb. Juxtamedullary Nephrons- Renal corpuscle deep in cortex withlong nephron loops- Receive blood from peritubularcapillaries and vasa recta- Ascending limb has thick and thinregions- Enable kidney to secrete very concentrated urine- Concentrate urine- more organized blood capillariesDescribe the tubular reabsorption and secretion: Much of the filtrate is reabsorbed by both active and passive processes.- Especially water, glucose, amino acids, and ions- Secretion helps to mange pH and rid the body of toxic and foreign substancesc. Transcellular Route:- Luminal membranes of tubule cells- Cytosol of tubule cells- Basolateral membranes of tubule cells- Endothelium of peritubular capillaries- Na+ reabsorbed via transcellular routed. Paracellular Route:- Between cells- Limited to water movement and reabsorption of Ca2+, Mg2+, K+, and some Na+ in the PCT where tight junctions are leaky-Microvilli (for absorption) on apical surface-Basolateral surface= absorbed into blood- Na/K ATPase= pulls 3 Na our and 2 K in- use gradient to pull things through to peritubullar capillares-Transport Mechanisms in the PCTAll occurring in the PCT:-Na-glucose symporter on apical side-Glucose facilitated diffusion on basolateral side- Increasing amounts of H+ going into the filtrate- on the apical side-Na-ion antiporter-CO2 dissolves in blood and can diffuse- carbonic anhydrase to make bicarbonate= adds to pH buffering system of blood- - reabsorbed some Na+-Na-ion antiporter-apical side= carbonic anhydrase= neutralizes the increasing H+ in urine/filtrateLate PCT- Passive Reabsorption-in late PCT- Lots of diffusion into peritubular capillary (moves from high to low concentration)- water also diffuses because “water follows salt”Describe the reabsorption in the Loop of Henle- Relatively impermeable to water, especially the ascending limb- Little obligatory water reabsorption- Na+ - K+ - 2Cl– symporters- no microvilli= little absorption- Na-K-2Cl Symporter= allows reabsorption of Na, K, and 2Cl – some K will leak backout- This apical membrane totally impermeable to water= no water movement but ions (salts) still moving= increasing ion concentration= increasing osmolarity and