Excretory System

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Excretory System

• Karen Kraus
• BIOL 204
• November 13, 2007

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Layout

• Waste removal
• Fluid regulation
• Ion balance (including pH)
• Hormones
• Vitamin D
• Gluconeogenesis

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beanie

• Retroperitoneal, right is inferior to left
• Three coverings
• Cortex and medulla areas
• Functional unit is the nephron

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Feed me!
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connections
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Holding pattern
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filtration

• Filtration via hydrostatic pressure
• NFP GHP (BOP CHP) 10mmHg
• Average fluid filtered into the capsule
  125ml/min
• Clearance
• Autoregulation, tubulo-glomerular feedback,
  renin-angiotensin

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Bring it back

• Many substances are returned
• Active and passive transports used
• PCT Na, K, nutrients, urea, water, small
  proteins
• LH water, electrolytes
• DCT Na, Ca, Cl, water (hormonally controlled)
• CD water, Na (hormonally), urea, other ions

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Adding a little something

• Toxins, some neurotransmitters
• Waste products (urea, uric acid)
• Aldosterone controls potassium secretion
• Hydrogen ions to control plasma pH

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Concentrate!

• Juxtamedullary nephrons
• Work to create conditions appropriate for water
  reabsorption
• ADH stimulates aquaporin channels in the CD, to
  reabsorb water

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Whats your recipe?

• 1-2 liters/day
• pH 6
• 95 water
• Various solutes, including urea, uric acid
  (urate), creatine, and ions (esp. Na, K,
  phosphate, sulfate, and some calcium, magnesium
  and bicarbonate)
• Abnormal? Glycosuria, hematuria, proteinuria, etc.

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expulsion

• Similar to defecation reflex
• Stretch receptors
• Contraction of detrusor
• Pressure against internal urethral sphincter
• Relaxation of external urethral sphinter