What is the Difference Between Ascending and Descending Loop of Henle?

The Loop of Henle, located in the kidneys, is a tubular structure that plays a crucial role in the filtration and concentration of urine. It consists of two segments: the ascending loop and the descending loop. The main differences between these two loops are:

1. Thickness: The ascending loop is thicker than the descending loop.
2. Permeability: The descending loop is permeable to water, while the ascending loop is permeable to ions rather than water. The descending loop has a high permeability to water, moderate permeability to urea, and low permeability to ions.
3. Location: The descending loop is the initial segment of the Loop of Henle, located between the proximal convoluted tubule and the ascending loop. The ascending loop, on the other hand, is the second segment, located between the descending loop and the distal convoluted tubule.
4. Structure: Both the ascending and descending loops have thick and thin segments, but they are not distinguishable in the descending loop. The descending loop is composed of simple squamous epithelium (thinner portion) and simple cuboidal epithelium (thicker portion).

In summary, the ascending loop of Henle is thicker, impermeable to water, and permeable to ions, while the descending loop is thinner, permeable to water, and located at the beginning of the Loop of Henle.

Comparative Table: Ascending vs Descending Loop of Henle

Here is a table comparing the differences between the ascending and descending loops of Henle:

The ascending loop of Henle is located between the descending limb and the distal convoluted tubule, while the descending loop is located between the proximal tubule and the ascending limb. The ascending loop is thicker than the descending loop. The ascending loop is permeable to ions and reabsorbs them, making the nephritic filtrate hypotonic. In contrast, the descending loop is permeable to water and does not reabsorb ions, making the nephritic filtrate hypertonic.