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-Excretion (primary): filter blood plasma - separate waste from useful chemicals
-Regulate blood volume and pressure
-Regulate osmolarity of fluids
-Secrete enzyme renin
-Secrete hormone erythropoietin
-Contribute to calcium homeostasis (synthesizes calcitrol)
-synthesize glucose in extreme starvation
Composed of 1.25 million nephrons
Contains glomeruli, proximal and distal tubules of nephron
Flow of Urine from Urinary Bladder (Male)
Urinary bladder - preprostatic urethra - prostatic - membraneous urethra - Spongy urethra
Renal A. - Segmental A. - Interlobar A. - Arcuate A. - Interlobular A. - Afferent arteriole - Glomerulus - Efferent arteriole - Peritubular capillaries or vasa recta - Interlobular V. - Arcuate V - Interlobar V. - Renal V.
1. Glomerular filtration
2. Tubular re-absorption and secretion
3. Water conservation
-Production of filtrate
-Reabsorption of water and ions
-Reabsorption of organic nutrients
-Secretion of waste products into tubular fluid
creates plasmalike filtrate of blood
-driven by high blood pressure in glomerular capillaries
-water and small solutes removed from plasma, barriers hold back blood cells and proteins
-controlled by renal autoregulation, sympathetic nervous system control, and hormones
Tubular Reabsorbtion and Secretion
Removes useful solutes from filtrate and returns to blood; removes additional wastes from blood and adds to filtrate
-GFR in excess of rate of urine output
-99% of filtrate reabsorbed, 1-2% excreted as urine
Proximal Convoluted Tubule (PCT)
Reabsorbs 65% of glomerular filtrate via osmotic and co-transport mechanism with NA+
-Released into peritubular capillaries
Osmotic gradient in renal medulla, necessary for collecting duct function
Reabsorbs 25% of filtrate
Distal Convoluted Tubule (DCT)
-Actively secretes ions, toxins, drugs
-Regulated by hormones
-Completes process of determining chemical concentration of urine
Removes water from urine and returns to blood, concentrates waste
Rate of water loss controlled by antidiuretic hormone (ADH) via aquaporins
-Closer to renal medulla
-Nephron loops extend deep into renal pyramids
-Responsible for salinity gradient, helps conserve water
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