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The Urinary System1

Metabolism involves wastee.g. CO2 (out through the lungs)e.g. nitrogen from protein metabolismConverted to ammonia and eventually urea2

The systemFilter almost everything from blood to tubulesReabsorb what we need back to bloodGet rid of the waste via the tubules3

The Urinary SystemAnatomy of the kidneyFiltration: mechanism and regulationReabsorption at the cellular levelSecretionHow we retain water and sodiumADH and aldosterone in regulation

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~2 M nephrons in a human body51) FiltrationMovement of material into the capsule to form a filtrate2) ReabsorptionSolutes and water are reabsorbed into the interstitial fluid and from there, into the blood3) SecretionSolutes are secreted from the blood into the filtrateSilverthorn

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The filtration membrane acts as a mechanical filter (no active transport)

Blood pressure in the glomerulus is high- Afferent arterioles have ___________than efferent arterioles

7Physiology of filtration - Blood pressure in the glomerulus is high- The filtration membrane is highly permeable - 2 M nephrons = huge surface area (larger than the skin!)

_____________________(GFR) 180 L/day (glomerular beds)4 L/day (rest of the beds combined)8Regulation of Glomerular FiltrationIntrinsic- Renal autoregulationExtrinsic- Neural controls- Hormonal mechanism9Auto-regulation (just 1 example)- Can keep a stable GFR in systemic blood pressure of 90-180 mm Hg- e.g. decreased systemic BP would lead to __________ of the afferent arterioleMyogenic stretch receptors in the afferent arteriole respond to changes in pressure- ________ diameter of afferent = ________ resistance = ________ local pressure gradients = adjusted blood flow

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- Norepinephrine and epinephrin are released by the sympathetic nervous system and the adrenal medulla - Afferent arterioles _______ and filtration is _______ - adequate systemic BP to sustain blood flow to heart and brain Extrinsic regulation (just 1 example)Goal: to regulate systemic BPWhat happens when the systemic BP is too low (