Loop of Henle or nephron loop in the kidney is a tubule that opens from the proximal convoluted tubule (PCT) and leads to the distal convoluted tubule. Its vital role is to produce a concentration gradient in the kidney and help in the filtration process. Its structure is composed of a thin descending loop and an ascending loop.
Ascending Loop of Henle
This loop runs downstream from the descending loop. The descending loop leads to a sharp bend, after which the ascending loop continues. The ascending loop has a thin and thick portion. The thick ascending limb is called the distal straight tubule. This drains into the distal convoluted tubule (DCT).
- The thin segment is permeable to ions and impermeable to water. Here, the salt moves out due to osmotic pressure.
- The medullary thick ascending limb is impermeable to water. Thus, the majority of reabsorption through active transport takes place here. It helps in the symport/transport of Na-K-Cl ions.
- The cortical thick ascending limb drains urine into the DCT.
Descending Loop of Henle
It is the first segment of Henle’s loop. The descending loop is thinner than the ascending loop. It also has thick and thin segments like the ascending loop, but they are not distinguishable. The thinner portion of the limb is composed of simple squamous epithelium, and the thick portion is composed of simple cuboidal epithelium.
The descending portion has a high permeability to water, moderate permeability to urea and low permeability to ions. The concentration of urine increases in this limb.
Difference between Ascending and Descending Loop of Henle
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Ascending Loop of Henle |
Descending Loop of Henle |
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It is the second segment of Henle’s loop that starts after the descending loop. |
It is the initial segment of Henle’s loop that starts after the proximal convoluted tubule. |
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It is located between the descending limb and the distal convoluted tubule. |
It is located between the proximal tubule and the ascending limb. |
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This portion comes after the sharp U-shaped bend of Henle’s loop. |
This portion comes before the sharp U-shaped bend of Henle’s loop. |
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It is thicker when compared to the descending loop. |
It is thinner when compared to ascending Henle’s loop. |
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The urine is less concentrated as the ions are pumped out. |
The urine is more concentrated as the water is pumped out. |
Also Read: Nephron – Function of Renal Tubules
Frequently Asked Questions
What is a renal tubule?
It is a long tubular structure that is filled with fluid from the glomerulus. It is composed of the proximal convoluted tubule, Henle’s loop (both ascending and descending), distal convoluted tubule and the connecting tubule. This whole tubule helps in carrying the filtered fluid.
What is a symporter?
It is a type of transporter protein that helps in the movement of two different substances across the cell membrane. In a symporter, the two different molecules travel in the same direction. There is a Na-K-Cl symporter present in Henle’s loop.
Extended Reading: Urine Formation and Osmoregulation
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