Countercurrent Mechanism

Q. Which of the following factors is responsible for the formation of concentrated urine?

1. Hydrostatic pressure during glomerular filtration
2. Low levels of antidiuretic hormone
3. Maintaining hyperosmolarity towards the medullary interstitium in the kidneys
4. Secretion of erythropoietin by juxtaglomerular complex

Q. Counter current mechanism helps in concentrating urine in animals and mainly operates on:
a. Henle's loop b. Vasa-recta
c. PCT d. DCT

1. a only
2. b only
3. a and b
4. All of these

Q. Osmoregulation is concerned with

1. The removal of nitrogen from the body
2. Concentrations of salt and water in the body
3. Osmotic properties of cell membranes
4. pH of the blood

Q. Which feature enables the mammalian kidney to concentrate urine in the medullary region ?

1. Maintaining a high osmotic pressure in the tissues between the tubules.
2. Rapid removal of sodium ions from medullary tissue.
3. High oxidative metabolism of medullary cells
4. Rapid flow of blood through the medulla

Q. The ascending limb of the loop of Henle, transports solutes (NaCl) out of the tubule lumen with little or no water, generating a hyperosmotic medullary interstitium and delivering a hypoosmotic tubule fluid to the distal tubule. This is called the _____.

1. Flow of fluid
2. Single effect
3. Countercurrent multiplier
4. Flow of filtrate

Q.

what is the function DCT

Q.

Give a brief account of the counter current mechanism.

Q.

If DCT is impermeable to water, how can it be stimulated to release water even by aldosterone??

Q. explain the terms myogenic autoregulation in kidneys, capsular hydrostatic pressure and blood colloidal osmotic pressure.

Q. Which one of the following statements in regard to the excretion by the human kidneys is correct?

1. Distal convoluted tubule is incapable of reabsorbing bicarbonate ions
2. Descending limb of loop of Henle is impermeable to water.
3. Nearly 99 per cent of the glomerular filtrate is reabsorbed by the renal tubules.
4. Ascending limb of loop of Henle is impermeable to electrolytes.

Q.

Regarding the assertion and reason, choose the correct option.

Assertion [A]: The filtrate that moves from the PCT to the loop of Henle, remains isosmotic.

Reason [R]: About 50% of urea is reabsorbed.

1. Assertion [A] is True and Reason [R] is False.

2. Reason [R] is True and Assertion [A] is False.

3. Assertion [A] is True and Reason [R] is True and is a correct explanation to [A].

4. Assertion [A] is True and Reason [R] is True but is an incorrect explanation to [A].