11 Nephrons A kidney has 1 million of these Smallest unit of filtration Blood supply to nephronBlood taken to nephron by afferent arterioleEfferent arteriole takes filtered (but not deoxygenated blood) to peritubular capillaries (surround tubes of nephron)
28 OverallNet filtration pressure forces substances out of glomerulus and into capsule
29 Factors Affecting Filtration Change in diameter of arteriolesSmaller afferent arteriole = less filtrationSmaller efferent arteriole = more filtrationLess proteins in blood = less glomerular osmotic pressure = more filtrationMore pressure in capsule = less filtration
30 Reabsorption Mostly in proximal tubule MicrovilliGlucose, amino acids, water, proteinThere is a limit to reabsorption, so these are still excreted in urine as well
32 SecretionOpposite of reabsorptionExcess H ions and organic compounds
33 Urine CompositionVaries from time to time; reflects the amounts of water/solutes that the kidneys eliminate to maintain homeostasis95% water, and also contains urea, uric acid, a trace of amino acids, and electrolytes
34 Urine Elimination Pathway of urine after forming in nephron: Collecting DuctMinor calycesMajor calycesRenal PelvisUreterBladderUrethraOUT!
38 Bladder Muscular, hollow, sphere, highly folded Stores urine, forces it into urethra
39 Micturition Reflex Process by which urine leaves bladder Stretching of bladder detected by micturition reflex center of spinal cordCauses:Bladder muscle contractionUrge to urinateInternal urethral sphincter relaxesExternal urethral sphincter relaxes (voluntary control)
40 UrethraOpening from bladder to external environment
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