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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
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