Regional specialization of the renal tubules
3 important questions on Regional specialization of the renal tubules
Explain the non-regulated reabsorption in the proximal tubule.
- 70% of the Na and water that is filtered in the proximal tubule is reabsorbed --> mass absorber.
- Function is to absorb the bulk of filtered solutes and water, thereby preventing their loss from the body. Ongoing process that is NOT regulated.
- Apical membrane is highly folded into many microvilli (brush border).
- Transporting cells contain lots of mitochondria that facilitate the ATP to drive all the active transport.
- Tight-junctions between epithelial cells have high permeability for water and small solutes (leaky epithelium).
Explain the regulated reabsorption and secretion in the distal tubule and collecting duct.
- Much less microvilli
- Fewer mitochondria
- Tight junctions are far less permeable (tight epithelium)
- Receptors for hormones that regulate transport of water and solutes
Explain the water conservation in the Loop of Henle.
The juxtamedullary nephrons create an osmotic gratient in the renal medulla, such that the fluid in the outer part of the medulla is at lower osmolarity than the fluid at the inner portion of the medulla. This gradient is critical for water retainment.
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