medullaThe thin ascending limb is found in the medulla of the kidney, and the thick ascending limb can be divided into a part that is in the renal medulla and a part that is in the renal cortex. The ascending limb is much thicker than the descending limb.
loop of Henle, long U-shaped portion of the tubule that conducts urine within each nephron of the kidney of reptiles, birds, and mammals. The principal function of the loop of Henle is in the recovery of water and sodium chloride from urine.
The key difference between ascending and descending loop of Henle is that ascending loop of Henle is the thicker segment of the loop of Henle located just after the sharp bend of the loop while descending loop of Henle is the thinner segment located just before the sharp bend of the loop.
1) Ascending limb of loop of Henle is impermeable to electrolytes, but is permeable to water.
The thick ascending limb occupies a central anatomic and functional position in human renal physiology, with critical roles in the defense of the extracellular fluid volume, the urinary concentrating mechanism, calcium and magnesium homeostasis, bicarbonate and ammonium homeostasis, and urinary protein composition.
The descending portion of the loop of Henle is extremely permeable to water and is less permeable to ions, therefore water is easily reabsorbed here and solutes are not readily reabsorbed.
The thin descending limb turns back on itself, ascending towards the medulla, and the epithelial cells become cuboid, rich in mitochondria and have an invaginated luminal surface. The thick ascending limb extends towards the glomerulus of the same nephron and then leads into the distal convoluted tubule.
So, the correct option is 'The ascending limb of the loop of Henle is impermeable to water. '
The descending limb is permeable to water, but has low permeability to Sodium. As the filtrate travels down the descending limb the water leaves by osmosis because of the salty environment into the medulla.