Question

Which of the following statements is correct?
A. The descending limb of the loop is Henle is permeable to electrolytes.
B. The ascending limb of the loop of Henle is impermeable to water.
C. The descending limb of the loop of Henle is impermeable to water.
D. The ascending limb of the loop of Henle is permeable to water.

Answer 1

Let’s recall, that Loop of Henle is a U-shaped long portion of the tubule which conducts urine in each of the nephrons of the kidney of birds, reptiles, and mammals, and principal function of the loop of Henle is to recover water and sodium chloride from urine. You should keep in mind, the loop of Henle is divided into three main parts or segments: the thin descending limb, the thin ascending limb, and the thick ascending limb (also referred as the diluting segment).

Complete answer:
Now as we already know, the loop of Henle can be divided into three main parts:
1. Thin descending limb of loop of Henle, has low permeability to urea and ions but highly permeable to water. Remember, the loop is sharply bent in the renal medulla going from descending to ascending thin limb.
2. Thin ascending limb of loop of Henle- It is impermeable to water, but it is permeable to ions.
3. Ascending limb of the loop of Henle- Here the potassium, Sodium, and chloride ions are reabsorbed from the urine. More reabsorption of Na ions is driven by the electrical and concentration gradient , as well as other cations such as magnesium and calcium ions.
Hence, we know that the Henle's loop maintains the concentration of urine whereas, descending loop of Henle is permeable to water but is impermeable to electrolytes. The ascending loop is impermeable to water and allows electrolytes transport.

Additional information:
Remember the type of tissue of the loop is simple squamous epithelium, and the "thick" and "thin" terms do not refer to the size of the lumen, but refers to the size of the epithelial cells. Note that the loop is also sometimes referred to as the Nephron loop.

Therefore, the correct answer is option B.

Note:- Always keep in mind, the loop of Henle is a portion of a nephron which leads from the proximal convoluted tubule (PCT) to the distal convoluted tubule(DCT). It is discovered by and named on, the German anatomist Friedrich Gustav Jakob Henle. It’s important to note that the loop of Henle's main function is to create a concentration gradient in the kidney medulla.