Question

The mechanisms that establish the medullary osmotic gradient depend mostly on the properties of the __________.

a. collecting duct
b. distal convoluted tubule
c. loop of Henle
d. glomerular filtration membrane

Answer 1

The establishment of the medullary osmotic gradient is primarily attributed to the function of the loop of Henle, which acts as a countercurrent multiplier through differential permeability of its ascending and descending limbs.

Step-by-step explanation:

The mechanisms that establish the medullary osmotic gradient depend mostly on the properties of the loop of Henle. Within the loop, the descending limb is permeable to water but not to solutes, allowing water to be absorbed into the surrounding high-salt-concentration medulla, thereby concentrating the filtrate. In contrast, the ascending limb is impermeable to water but allows the passage of ions such as Na+ and Cl-, contributing to the creation of an osmotic gradient.

This system acts as a countercurrent multiplier, intensifying the osmotic gradient that is critical for the concentration of urine. The surrounding vasa recta, in turn, functions as a countercurrent exchanger, maintaining the gradient established by the loop of Henle.

Answer 2

The medullary osmotic gradient, crucial for urine concentration, is primarily established by the loop of Henle's ability to absorb water and transport solutes, functioning as a countercurrent multiplier.

Step-by-step explanation:

The mechanisms that establish the medullary osmotic gradient depend mostly on the properties of the loop of Henle. In the loop of Henle, the permeability of the membrane changes.

The descending limb is permeable to water, allowing it to absorb water from the filtrate due to the high osmotic pressure in the medulla. Conversely, the ascending limb is impermeable to water but allows for the active and passive movement of solutes like Na* and Cl- out of the filtrate, which contributes to the osmotic gradient.

This system, acting as a countercurrent multiplier, is crucial in concentrating urine and maintaining the body's water balance.