Function Structure of the Nephron Function of Kidneys: • • • Regulate: water and electrolyte balance, pH, blood pressure Excrete: metabolic waste products, foreign chemicals/drugs Secrete: renin, erythropoietin (EPO), 1-25dihydroxyvitamin D3 (the kidney hydroxylates 25-hydroxyvitamin D2 (calcidiol) into calcitriol) Gluconeogenesis Nephron Development • The PCT and DCT developed to prevent salt loss as life moved from saltwater to freshwater • The LoH developed to conserve water as life became terrestrial Types of Nephrons Glomerular Filtration • • • • GFR: 125mL/min or 7.5L/hr or 180L/day Therefore, the entire plasma volume (~3.5L) is filtered ~50x/day Renal arteriole endothelium is fenestrated (70nm) to allow water flow Podocytes have pedicles/foot processes which interdigitate to produce filtration slits covered by filtration flit diaphragms (4-14nm) • Negatively charged surface proteins (glycoproteins) cause anion selectivity What is Filtered? • • Water, inorganic ions and small organic solutes (MW<7000) The concentration of inorganic ions and small organic solutes equals the concentrations in the plasma • • • Almost no protein or cells MW >70 000: not filtered MW 7000 – 70 000: selectively filtered based on size and charge