Anatomy and Physiology Exam 3 Study Guide.docx - Functions...

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Functions of the urinary system : filter blood, regulate fluids (electrolytes, acids, bases), produce hormones to regulate Ca2+ and BP The Nephron : Cells of the Nephron—cortical cells filter (most abundant), Juxtamedullary cells concentrate urine Filtration barrier: 1. Fenestrated capillaries filter based on size 2. Basement membrane filters based on charge 3. Podocytes filter based on size and charge What gets filtered ? Water, electrolytes, HCO3-, glucose, some amino acids (renal corpuscle) What gets reabsorbed ? 100% glucose, amino acids, and HCO3-, 67% water and Na+ (PCT and loop of Henle) What gets secreted ? Anything that wasn’t filtered (PO4 3-, K+, drug metabolites, urea) Peritubular capillaries and DCT GFR and pressure: afferent and efferent arterioles - Hydrostatic pressure of the glomerulus 50-55 mmHg, outward pressure - Hydrostatic pressure of bowman’s capsule 15mmHg, inward - Oncotic pressure of the glomerular capillaries 30mmHg, inward - Constrict efferent arteriole and dilate afferent = increase pressure and GFR - Dilate efferent and constrict afferent = decrease pressure and GFR Regulation: - Macula Densa cells sense the amount of Na+ in DCT and can cause the efferent arteriole to constrict or dilate based on NaCl levels. High NaCl = constriction of efferent arteriole, Low NaCl = dilate efferent arteriole - Renin-Angiotensin-Aldosterone System : kidneys release renin in response to low GFR or BP, renin activates Angiotensin II which causes aldosterone release, constriction of efferent arteriole, systemic vasoconstriction, ADH release, increase

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