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What are three functions of the urinary system?
- Produce and excrete urine
- Regulate plasma volume and blood pressure
- Excrete toxic by-products (ie. urea) into duct-like system
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Describe the overall structure of the kidney.
- Dense irregular CT capsule
- Blood vessels and ureter enter/exit at the hilium
- Outer=cortex, inner=medulla
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What is the vascular pole of a renal corpuscle?
Area where blood vessels enter/exit as either afferent or efferent arterioles
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What are podocytes?
specialized visceral layer cells which line the glomerular capillaries
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What type of capillaries are the glomerular capillaries?
fenestrated capillaries
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What does the glomerular filtration barrier consist of?
- Fenestrated capillary endothelium
- Basement membrane (2 that fuse- one on each side)
- Slit diaphragms (specialized ECM) between pedicels (foot processes) of podocytes
- slit diaphragms are filled with glycoproteins
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What is the glomerular filtrate composed of?
- High concentrations of water, glucose, ions, and urea.
- No plasma proteins because the glycoproteins in the slit diaphragms prevent their passage through the filtrate barrier
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Describe the structure of the proximal tubule.
- Simple cuboidal epl
- Microvilli for increased resorbtion from lumen
- Numerous mitochondria due to high energy requirements for active transport
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How does resorption occur in the proximal tubule?
- Resorption is active, both pump and vesicle based
- Resorption releases water, ions, glucose, and a.a's into the peritubular CT (interstitum) and is returned to the peritubular capillaries
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Describe the structure of the descending limb of the Loop of Henle.
- simple squamous epithelium
- water permeable due to aquaporins- water flows out into salty medulla
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Describe the structure of the ascending limb of the Loop of Henle.
- Simple squamous epl
- many tight junctions
- Water impermeable- no aquaporins
- As it ascends, epl becomes cuboidal and starts pumping NaCl out into medulla
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Describee the structure of the distal tubule.
- Simple cuboidal epl
- water impermeable
- Continues to pump NaCl out of filtrate
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What are mesangial cells?
- Macrophages
- Extraglomerular cells have phagocytic and contractile functions
- Intraglomerular cells just have phagocytic functions
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