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VCU PHIS 206 - Exam 3 Study Guide
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PHIS 206 1st EditionExam # 3 Study Guide Lectures: 20 - 29Lecture 20I. Functions of the Kidneys-maintain fluid levels-maintain electrolytes balance-eliminate metabolic waste productsII. Excretory System-kidneys and urinary bladder-kidneys surrounded by capsuleo inside capsule is the cortex (looks like red meat)o inside cortex is the dull, grey medulla 3 pipeso renal artery: entrance of the kidneyso renal vein/ureter: exit of kidneyso What went in has to = what went outIII. Nephron-structure that does kidney stuf- Bouman’s capsule: anatomical cup; wrapped around capillaries aferent and eferent arterioles  double-walled with space in between opens 1st to proximal convoluted tubule proximal convoluted tubule: opens to Loop of Henle descending (thin) and ascending (several layers thick)o ascending opens to distal convoluted tubule-Renal artery carries 25% of fluidIV. 2 Types of Nephrons-cortical: kidneys, Bouman’s capsule, and tubules; 80% total-juxtamedullary: ONLY Loop of Henle; 20% totalV. Blood Supply -afferent arterioles: 100% that goes into renal artery-efferent arterioles: break into peritubular capillaries  peritubular capillaries: 80% around Loop of Henle-renal cortex looks like red meat b/c it has a large red blood supply-Loop of Henle’s juxtamedullary are long and rather straight, so peritubular capillaries around Loop are long and straight Peritubular capillaries known as vasa recta (meaning long)VI. 3 Processes1.) Filtration: process in which fluid is pushed out of the plasma to Bouman’s capsule-known as glomerular -plasma w/ protein removed: filtered-tubular identical to plasma but no proteins-so blood in efferent has more protein than afferent2.) Reabsorption: as tubular fluids move along nephron, some things are reabsorbed-active + passive transport3.) Secretion: some things are secreted out using plasma-what comes out will not be same as what was in Bouman’s capsuleVII. Filtration-glomerulal capillaries drain into arterial vein pressure in glomerulal capillaries is higher glomerulal capillaries not in straight line; look like spaghet vary pressure by constricting/relaxing aferent or eferent-filter by manipulating arterioles that feed it-180 L/day = 125 mL/min: normal glomerular filtration rate (GRF)-avg. urine volume= 1 L/day reabsorb: 179 L/dayVIII. Reabsorption-reabsorb 99% of solutes using active transport-about 40-45% of solutes in plasma are Na+ ions must reabsorb 99% so Na+ ions must be absorbed too therefore, use ACTIVE TRANSPORTIX. Pressure Difference-Bouman’s capsule (hydrostatic pressure) ≈ +50 mmHg in glomeruli-Pressure pushing in (colloid osmotic pressure) ≈ -30 mmHg in glomeruli-Hydrostatic pressure ≈ -10 mmHg in Bouman’s capsule-Net driving force = 10 mmHg gives Gfr or 125/mino directly proportional to pressure-10 mmHg kept constant in real life-When arterial pressure increases, pressure in glomeruli stays same b/c we constrict aferent arterioles Gfr is constant-No urine production when 60 mmHg (of renal curve) or less b/c when arterial pressure is low, pressure in glomeruli cannot get biggerX. Reabsorption and Active Transport-reabsorption in arteriole tubules is high-100% glucose reabsorbed if healthy b/c no glucose in urine 1 mg/mL of glucose in plasma 1 g/8 min reabsorbed -Reabsorb by active transport same with amino acids, vitamins, etc…-Active transport systems that make this happen MUST reabsorb Na+ ions to reabsorbother things more than 99% of filtered Na+ is reabsorbed- Na+ Reabsorption 80% in proximal, 12% in Loop of Henle, and 8% in distal tube-distal tubule can control what we reabsorb-Hypertensive: take of Na+ (in diet) b/c plasma is enlarging; reabsorption problemsLecture 21I. Glucose-100% reabsorbed for a normal person-only fuel brain can use-active transport system: all reabsorbed in proximal tubule-must have a carrier protein that is saturable input of Energy moves it outside nephron finite capacity that the protein can carry-Maximum rate: transport maximumamount entering: tubular loado concentration in glomerulal filtrate × filtration rate- Transfer Maximum: Tm (Glucose) = 400 mg/min - Normal Tubular Load = 125 mg/min 100% gets reabsorbed in proximal tubule- Plasma Glucose Level 1 min 125 mg/min 0 in urine 2 min 250 mg/min 0 in urine 3 min 375 mg/min 0 in urine 4 min 500 mg/min 100 in urine 5 min 625 mg/min 225 in urine 6 min 750 mg/min 350 in urineII. Diabetes-Diabetes melatis: “honeylike”-Diabetes insipitis: “without sugar”greater than Tm = 400 mg/minIII. Active Reabsorption of Na+-causes passive reabsorption of Cl- since cation (of Na+) and anion (of Cl-) must equal out-When Na+ and Cl- reabsorbed, water follows osmoticallyIV. Passive Reabsorption-things can difuse out of nephron passively best example: urea (non-toxic)-most aquatic animals produce ammonia that difuse away fast before storage we have to convert toxic ammonia to something safer convert ammonia into urea-urea is 2nd fastest to difuse, after water-osmotically reabsorb water, as water decreases, urea increases urea difuses up when left in high concentrations-sequence of events1. Actively transport solutes2. Water follows (PASSIVE)3. Things that can diffuse (urea) will diffuse down conc. gradient (PASSIVE)-urea more in plasmaV. Secretion-add stuf to tubule add Extracellular Fluid in tubules, which is plasma in capillaries-actively transfer into nephron from capillaries-MOST IMPORTANT THING SECRETED: H+ proximal, distal, collecting vessel-Number of anions actively secreted too-Anionated groups attach to drugs and are excreted through urineVI. Urine Output-1-2 L/day: normal urine output ≈ 1 mL/min-Gfr = 180 L/day-urine output = 1 L/day VII. Plasma Clearance-know how much you are excreting and concentration of stuf in plasma, then you know the number of mL of plasma to provide some specific compound each minute (Definition of Plasma Clearance)-plasma clearance tells you how efficiently you are removing the compound from the kidneys-plasma clearance large to provide stuf that is actively secretedReabsorbed 179 L/dayVIII. Inulin-freely-filtered, but not reabsorbed or secreted-amount in glomerulal filtrate is amount that entered-if you measure inulin clearance, you are actually measuring the Gfr-not normal in blood unless you love garlic or artichokesIX. Creatinine-creatinine clearance also gives you


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VCU PHIS 206 - Exam 3 Study Guide

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