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
Describe the overall structure of the kidney.
- Dense irregular CT capsule
- Blood vessels and ureter enter/exit at the hilium
- Outer=cortex, inner=medulla
What is the vascular pole of a renal corpuscle?
Area where blood vessels enter/exit as either afferent or efferent arterioles
What are podocytes?
specialized visceral layer cells which line the glomerular capillaries
What type of capillaries are the glomerular capillaries?
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
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
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
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
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
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
Describee the structure of the distal tubule.
- Simple cuboidal epl
- water impermeable
- Continues to pump NaCl out of filtrate
What are mesangial cells?
- Extraglomerular cells have phagocytic and contractile functions
- Intraglomerular cells just have phagocytic functions