How is water reabsorbed in the collecting duct?
Reveal answer
Medulla salty → water leaves duct by osmosis → into blood.
Key words: osmosis
3(i) EXCRETION · RECALL
3.26B Reabsorption of water from the collecting duct
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More permeable collecting duct means?
Reveal answer
More water reabsorbed → smaller volume, more concentrated urine.
Key words: concentrated
Which part of the nephron makes the medulla salty?
Reveal answer
The loop of Henle.
Key words: loop of Henle
Why is a dehydrated person's urine dark?
Reveal answer
More water reabsorbed → urea and pigments concentrated.
Key words: reabsorbed
What is meant by the term aquaporin?
Reveal answer
Membrane channel that permits rapid water movement.
Key words: aquaporin
What is meant by the term medulla?
Reveal answer
Inner kidney region containing loops of Henle and collecting ducts.
Key words: medulla
Collecting-duct states: for Many aquaporins/high permeability, give the water reabsorption and the urine outcome.
Reveal answer
Water reabsorption: More. Urine outcome: Low volume, concentrated.
Key words: Many aquaporins/high permeability
Collecting-duct states: for Few aquaporins/low permeability, give the water reabsorption and the urine outcome.
Reveal answer
Water reabsorption: Less. Urine outcome: High volume, dilute.
Key words: Few aquaporins/low permeability
Collecting-duct states: for No water-potential gradient, give the water reabsorption and the urine outcome.
Reveal answer
Water reabsorption: Little net osmosis. Urine outcome: Permeability alone is insufficient.
Key words: No water-potential gradient
True or false, and why? “ADH carries water back to blood.”
Reveal answer
False. ADH changes duct permeability; water itself moves by osmosis.
True or false, and why? “Water is reabsorbed by active transport.”
Reveal answer
False. It moves passively down a water-potential gradient.
True or false, and why? “Concentrated urine contains more water.”
Reveal answer
False. It has more solute relative to water and usually a smaller volume.
Which part of the nephron adjusts how much water is reabsorbed?
Reveal answer
The collecting duct.
Key words: collecting duct
Why is a large volume of dilute urine made after drinking a lot of water?
Reveal answer
Collecting duct less permeable → less water reabsorbed → more water stays in the urine.
Key words: permeable
Where does water go after it is reabsorbed from the collecting duct?
Reveal answer
Into the blood capillaries.
Key words: blood