L 24 Excretion - EXCRETORY SYSTEM Under the segmental...

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EXCRETORY SYSTEM
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Under the segmental somites therefore segmented themselves into NEPHROTOMES In each nephrotome is a NEPHRON
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NEPHRON consists of two layered cup of epithelium = RENAL CAPSULE (Bowman’s capsule). Capsule envelops a knot of capillaries = GLOMERULUS with an afferent arteriole and an efferent arteriole. Whole thing = RENAL CORPUSCLE. Rest is simple epithelial tube which varies among vertebrates - proximal tubule = absorptive; variable length intermediate tubule; distal tubule; collecting tubules; excretory duct.
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Filtration mechanism increased by 1. 2 arterioles (rather than ateriole and veinule) and efferent smaller so pressure increases. 2. Diffusion distance short, capillaries fenestrated, filtration slits on podocytes. Larger molecules held back (< 60K m. wt) everything else goes through. Amino acids, water, sugars recovered, rest eliminated.
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Podocyte feet form outer diffusion barrier
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Recovery takes place in the tubules through selective resorption, leaving urine to be excreted. Resorption into PERITUBULAR CAPILLARIES Blood supply varies: A = efferent renal + renal portal vein; B = renal portal vein; C = efferent renal
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Proximal and distal convoluted tubules have microvilli for absorption
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Most vertebrates have the nephron described = internal glomeruli. The first few nephrons at anterior end of
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This note was uploaded on 08/28/2011 for the course ZOO 3713c taught by Professor Staff during the Spring '08 term at University of Florida.

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L 24 Excretion - EXCRETORY SYSTEM Under the segmental...

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