Tubular Reabsorption Flashcards
Tubular reabsorption
As the filtrate moves along the renal tubule, the useful substances needed by the body are reabsorbed back into the blood in the capillaries surrounding the renal tubules. Mainly takes place in the proximal tubule
How is the proximal tubule adapted for reabsorption
- it is very long and coiled, which enables maximum reabsorption to take place
- a dense capillary network closely surrounds the tubule, so the substances can easily move into the bloodstream to be transported away
- walls are made up of cuboidal endothelial cells with the following adaptations:
1. A brush order of microvilli om their inner surface surface to increase the area for max reabsorption
2. The outer surface is folded further to increase the surface area
3. Many mitochondria to produce the ATP needed fir active transport
How does reabsorption take place
Some substances are actively reabsorbed from the filtrate in the nephron into the bloodstream. Others are passively absorbed
Active reabsorption
When molecules move actively, they combine with a carrier molecule and may move against the concentration gradient, this process needs ATP
Passive reabsorption
About 65% of the water is passable reabsorbed by osmosis
What is the role of the loop of Henle
The function is to create a high concentration of salt in the medulla which is necessary for osmotic withdrawal of water from distal tubules and the collecting ducts. As a result the tissue fluid in the medulla becomes highly concentrated, and water will not follow
What is the final outcome
Water is actively conserves and passed back into the blood and not lost in the urine
