Kidneys and Water Balance plus problems

Kidneys and Water Balance plus problems - Kidneys Renal...

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Kidneys / Renal Physiology Functions: 1. Regulation of extracellular fluid volume 2. Regulation of osmolarity (blood osmolarity – 290 mOsM 3. Maintenance of ion balance (mainly Na+, also K+ & Ca++) 4. Homeostatic regulation of pH (too acidic – kidneys remove H+ and conserve HCO3-; not as fast as lungs) 5. Excretion of wastes (by-products of metabolism) and foreign substances (toxins, drugs) 6. Production of hormones (EPO – erythropoietin –regulates RBC synthesis; renin – enzyme regulates hormones involved in Na+ balance and BP regulation) Kidney anatomy (0.4% body weight; receive 20-25% cardiac output) Cortex (contain nephrons, glomeruli) Medulla Nephron Blood supply – portal system, glomeruli Tubular portion – Bowman’s capsule Proximal tubule Loop of Henle Descending limb Ascending limb Distal Tubule Collecting duct Three processes of the nephron 1. Filtration – filtrate (like plasma minus cells minus plasma proteins) a. Glomerular filtration affected by hydrostatic pressure of blood (favors flow in) flowing through glomular capillaries, colloid osmotic pressure (favors flow to capillaries) inside glomerular capillaries, and hydrostatic fluid pressure (favors flow to capillaries) in capsule b. Glomerular filtration rate (GFR) – the amount of fluid that filters into Bowman’s capsule per unit time (~125mL/min) i. GFR influenced by net filtration pressure and filtration coefficient (dependent on surface area of glomerular capillaries and permeability of glomerular capillary-Bowman’s capsule interface 2. Reabsorption – most takes place in proximal tubule a. Na+ reabsorption is across the epithelium b. Na+ dependent reabsorption – apical symport protein and basolateral facilitated diffusion carrier c. Urea – passive reabsorption 3. Secretion – the transfer of molecules from the extracellular fluid into the lumen of the nephron a. active process Glomerulus and Bowman’s capsule=renal corpuscle AMOUNT EXCRETED= AMOUNT FILTERED-AMOUNT REABSORBED+AMOUNT SECRETED
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