BRAINCAKECollecting Duct
The collecting duct receives filtrate from the distal convoluted tubules of several nephrons. It runs from the cortex down through the medulla to the renal pelvis, passing through the gradient of water potential set up by the loops of Henle. Its job is to control how much water is reabsorbed, and so how concentrated the urine will be.
Filtrate entering the collecting duct is dilute. The tissue fluid of the medulla around it has a lower water potential, which gets lower (more concentrated) deeper in the medulla. So, if the duct wall is permeable, water leaves the filtrate by osmosis all the way down the duct and is carried away by the blood capillaries.
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Key terms in this lesson
- aquaporins
- Water channel proteins in cell membranes whose number controls how permeable a membrane is to water.
- adh
- Antidiuretic hormone, released by the posterior pituitary, which increases the permeability of the collecting duct to water.
More in Homeostasis
- Proximal Convoluted Tubule
- Loop of Henle
- Countercurrent Multiplier
- Distal Convoluted Tubule
- Urine
- Adaptations
- Control of Osmoregulation
- ADH
All 41 lessons in Homeostasis · All Edexcel A-level Biology topics