BIOL 431 Urinary System study guide.docx

Renal tubules glomerulus specialized for filtration

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Renal tubules Glomerulus: specialized for filtration, fed and drained by arteriole. BP high because afferent arteriole larger in diameter than efferent arterioles. Arterioles are high-resistance vessels. Peritubular capillaries: Low pressure, porous capillaries adapted fro absorption of water and solutes. Arise from efferent arterioles. Stick to adjacent tubules into cortex, empty into venules.
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Juxtamedullary nephrons Vasa recta: Macula densa tall, closely packed of ascending limb, chemoreceptors, sense NaCl content of filtrate granular cells Smooth muscles cells of afferent arteriole, contain enzyme renin, mechanoreceptors, sense blood pressure in afferent arteriole extraglomerular mesangial cell between arteriole and tubule, interconnected with gap junctions, may pass signals between macula densa and granular cells. 8. What is the juxtaglomerular complex? One per nephron, involves modified portions of distal portion of ascending limb of nephron loop. Importatn in regulation of rate of filtrate formation and bp. 9. What are the three processes of urine formation? Glomerular filtration makes cell and protein free filtrate tubular reabsorption selectively returns 99% of substance from filtrate to blood in renal tubules and collecting ducts tubular secretion selectively moves substance from blood to filtrate in renal tubules and collecting ducts. 10. What are the structures that make up the filtration membrane? 1) endothelium that lines the glomerular capillaries; fenestrated endothelium 2) glomerular basement membrane; consists of collagen fibrils 3) podocytes, half foot processes 11. Describe the pressures that drive and oppose glomerular filtration. Outward pressures promote filtrate formation Hydrostatic pressure in glomerular capillaries = Glomerular blood pressure Chief force pushing water, solutes out of blood Quite high – 55 mm Hg (most capillary beds ~ 26 mm Hg) Because efferent arteriole is high resistance vessel with diameter smaller than afferent arteriole Inward forces inhibiting filtrate formation Hydrostatic pressure in capsular space (HPcs) Pressure of filtrate in capsule – 15 mm Hg Colloid osmotic pressure in capillaries (OPgc) "Pull" of proteins in blood – 30 mm Hg Sum of forces Net filtration pressure (NFP) 55 mm Hg forcing out; 45 mm Hg opposing = net outward force of 10 mm Hg 12. What is the glomerular filtration rate (GFR)? Volume of filtrate formed per minute by both kidneys (normal = 120–125 ml/min) 13. What are the intrinsic mechanisms of control of the GFR? Maintains nearly constant GFR when MAP in range of 80–180 mm Hg Autoregulation ceases if out of that range 2 types of real autoregulation Myogenic mechanism smooth muscle contracts when stretchd High BP smooth muscle stretches constriction of afferent arterioles restricts blood flow into glomerulus Protects glomeruli from damaging high BP Tubuloglmerular feedback mechanism Flow-dependent mechanism directed by macula densa cells; respond to filtrate NaCl concentration.
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