Reabsorption Flashcards
What does the glomerular filtrate straight from the Bowman’s capsule contain?
Water, glucose, amino acids, salt, ions
Where does glomerular filtrate from Bowman’s capsule enter?
The proximal convoluted tubule
What happens to glucose in the proximal convoluted tubule?
Enters the capillary endothelium cell by cotransport
Then into the blood/tissue fluid by facilitated diffusion (capillaries surround tubule)
How much glucose is re absorbed into the blood?
In a healthy individual: ALL OF IT
Water in glomerular filtrate movement out the proximal convoluted tubule
Is re absorbed into blood down a water potential gradient by osmosis in the blood/tissue fluid
Out of the proximal convoluted tubule
How much water is reabsorbed in the proximal convoluted tubule?
SOME
NOT all of it
What is in the glomerular filtrate that enters the loop of Henle?
Waste
Water left behind not absorbed into blood
Na+ ions
What happens at the upper ascending limb of the loop of Henle?
Na+ is actively pumped out the upper ascending limb of the loop of Henle
Into the tissue fluid
What happens when Na+ ions are actively pumped into the tissue fluid from the upper limb of Loop of Henle?
Lowers the water potential of the tissue fluid
More concentrated with Na+ ions
What happens when the water potential of the tissue fluid is lowered around the loop of Henle?
Water is drawn out by osmosis down a water potential gradient from the descending limb of the loop of Henle into the tissue fluid
Why does the water potential of tissue fluid decrease down the loop of Henle?
Because less water is drawn out the descending limb of the loop of Henle as it goes down so the water potential is lowered
The turning point of the loop of Henle contains…
A very large concentration of Na+ ions
And a low water potential as a lot was drawn out by osmosis into tissue fluid
High concentration of Na+ ions in turning point loop of Henle means when it ascends…
At the lower ascending limb, can move into tissue fluid from loop of Henle by FACILITATED DIFFUSION
Why is excess water in the urine (in collecting duct) drawn out?
Because there is a large concentration of Na+ ions in the tissue fluid (due to active transport and facilitated diffusion)
so down a water potential grad by osmosis, water in the collecting duct moves out
What happens to all Na+ ions and water that remains in the tissue fluid?
Absorbed into capillaries around loop of Henle and into the blood
Why does the loop of Henle act as a counter current multiplier?
Because the filtrate flows in opposite (ascending and descending) down loop of Henle
Water potential lower deeper into the medúlla
So at the bottom of ascending limb, Na+ ions are rapidly released into tissue fluid but smaller osmosis of H2O
And reverse for the upper limb
