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General Physiology

Kidney Test 2

Function of a kidney to regulate the composition and volume of body fluids
Nephrons the functional unit of the kidney
What is inside the renal corpuscle Glomerulus Glomerular (Bowman's) capsule Podocytes
What are the Renal tubules Proximal convoluted tubule Nephron loop Distal convolutes tubule Collecting duct
What does the nephron loop do sets up gradient for urine concentration in collecting duct -only in avian and mammalian kidney
What does the collecting duct do? recieves fluid from nephrons -adjusts H2O via ADH
Filtration conversion of blood plasma to primary urine due to hydrostatic pressure
Reabsorption movement of H2O and solutes from tubular fluid to blood
Filtrate/Capsular fluid fluid in capsular space -water and what passes through filtration -has little to no protein
Primary urine in PCT through DCT
Definitive urine Collecting duct
BHP or Pgc blood pressure in glomerular capsule -higher than other capillaries
CP hydrostatic pressure in capsular space -due to high rate of filtration
COP colloid osmotic pressure -no protein in glomerular filtrate
Net filtration pressure (NFP) remains high to ensure only filtration to the fluid exiting
Active solute secretion -solutes actively transported into tudule -water follows due to osmotic gradient so the volume increases -other solutes follow due to concentration gradient
Glomerular filtration rate (GFR) adjusted -turning on and off nephrons -changing the Pgc --vasoconstriction/ vasodilation of afferent/efferent arterioles ---increase Pgc increases net filtration pressure increases glomerular filtration rate
Urine formation in amphibians Proximal CT -freely permeable to water -Na+ is actively reabsorbed -Cl- is passively reabsorbed due to electrical gradient -fuid remains isosmotic with plasma because proportional amount of water follows
Urine formation in amphibians Proximal CT -glucose is reabsorbed by secondary active transport driven by primary active transport of Na+ -free amino acids also reabsorbed in the PCT
Urine formation in amphibians Distal CT -continues active reabsorption of NaCl -controls exccretion of pure/ osmotically free water --some water is required to excrete solutes --can control the amount above what is required for solute excretion (urine is hyposmotic relative to plasma) --uri
Urine formation in amphibians Distal CT max U/P ration in amphibians = 1 U/P= osmotic pressure of urine/ plasma
Marine teleosts -No DCT --structure specialized for dilute urine in high volume -relatively small glomeruli and small nephrons -low GFR -some are aglomerular --form urine by secretion in nephron
Diuresis production of an abundant (typically dilute) urine -diuretic hormones promote diuresis -anti-diuretic hormones means low urine (typically concentrated)
Water related hormones that affect diureses -Anti-diuretic hormone (ADH) -Aldosterone -Natriuretic hormones -Renin
Anti- diuretic hormone (ADH) -controls excretion of water; quantity above whats necessary to remove solutes -responsive to changes in blood and osmotic pressures
ADH cont -controls insertion/removal of aquaporins of DCT and collecting duct -high ADH->increased H2O permeability->increased H2O reabsorption->concentrated urine -low ADH->diluted and high volume of urine
ADH cont -decreases GFR in amphibians and reptiles by reducing # of active nephrons->decreased urine flow so better water retention -promotes active reabsorption of NaCl from tubules
Aldosterone -causes kidney to retain Na+ and excrete K+ -causes water to be retained as well -released when blood pressure is low
Natriuretic hormones -promote addition of Na+ to the urine -increases urine volume in response to high blood pressure
Renin GOAL: increase blood volume and pressure 1. widespread vasoconstriction raises mean arterial blood pressure and GFR 2. aldosterone secretion increase Na+ & H2O reabsorption 3. stimulates ADH release promotes water reabsorption 4. stimulates thirst
Urine formation in mammals Loop of Henle hairpin loop b/w PCT and DCT -anatomical reason mammals can make hyperosmotic urine
Concentrating Urine Descending Limb -permeable to water but not salt -osmolarity increases deeper into medulla "multiplies"
Concentrating Urine Ascending Limb -impermeable to water, active transport of Na+, K+, and Cl- -increases osmotic pressure of interstitial fluid and that of descending limb as water exits
Concentrating Urine Collecting Duct -Osmosis towards interstitial fluid makes urine become more concentrated as it passes deeper through medulla
Vasa Recta blood supply to medulla -pulls water out of interstitial fluid due to colloid osmotic pressure --keeps medullary conc. high makes osmosis (water) out of tubules, which makes concentrated urine
Juxtaglomerular apparatus macula densa and juxtaglomerular cells -regulates nephron function -source of RENIN, which helps control aldosterone, which helps in ion excretion
Tubuloglomerular feedback increase in NaCl in the PCT helps macula densa stimulate JG cells which constricts afferent arterioles, which decreases GFR
Morphology and urine concentration -short loop of henle is aquatinc mammals; no inner medula -prescence/adsence of renal papilla --indication of # and length of loop --most developed in arid species
Morphology and urine concentration Medullary thickness allometric -urine conc ability decreases with body size relative medullary thickness (MT/kidney size) is associated with habitat type
Morphology and urine concentration Relative medullary thickness greater thickness the longer the loops the more concentrated urine
Nitrogen Excretion -Ammonotelic -Ureotelic -Uricotelic
Ammonotelic ammonia or ammonium ions are principal nitrogen end product -primitive state -teleost fish, aquatic amphibians -NH3 highly toxic requires constants voiding -cheapest nitrogenous waste to produce
Ureotelic urea is the nitrogen product -elasmobranchs, adult terrestrial amphibians, all mammals -urea: more costly than NH3, but less toxic --less water required to expel nitrogen waste --excretaory passages have low permeability for urea
Ureotelic strategies -used for osmoregulation in elasmobranchs -chemosensory defense against predators -some aquatic ammonotelic species switch to ureotelic to conserve water
Uricotelic uric acid is nitrogen product -lizards, snakes, birds -low toxicity and solubility --conc in body fluids stay low even though accumulation if uric acid continues -reduced water cost helps urine excrete as semisolid pastes or powders
Created by: epannell