What is the loop of Henle permeable to?
The descending limb of the loop of Henle is permeable to water. Water diffuses into the hyperosmolar medullary interstitium. The osmolarity can reach a maximum of 1200 mOsm/L at the tip of the medullary interstitium in antidiuresis.
Why is ascending loop of Henle impermeable?
The thin ascending limb is impermeable to water, due to it having no aquaporin channels. However, Na+ reabsorption still occurs passively through epithelial Na+ (eNaC) channels. Chloride (Cl–) ions are also reabsorbed in the thin ascending limb through Cl– channels.
Is the ascending limb permeable to water?
The thick ascending limb actively reabsorbs NaCl but has an extremely low transepithelial osmotic water permeability, even in the presence of vasopressin (6).
How is calcium reabsorbed in the nephron?
More than 95% of filtered calcium is reabsorbed along the renal tubules. In the proximal tubules, 60% of filtered calcium is reabsorbed by passive mechanisms. In the thick ascending limb, 15% of calcium is reabsorbed by paracellular diffusion through paracellin-1 (claudin-16).
How does reabsorption occur in the loop of Henle?
The descending loop of Henle receives isotonic (300 mOsm/L) fluid from the proximal convoluted tubule (PCT). In the ascending portion, the loop becomes impermeable to water and the cells of the loop actively reabsorb solutes from the luminal fluid; therefore water is not reabsorbed and ions are readily reabsorbed.
What substances are reabsorbed in the ascending loop of Henle?
Reabsorption in the thick ascending limb: A further 25% of the sodium and potassium is reabsorbed through the walls of the thick ascending limb of the loop of Henle via: Three-ion cotransporter (sodium/potassium/chloride) and the sodium/potassium ATPase, which as before maintains the sodium concentration gradient.
What happens as the filtrate progresses up the ascending limb of the loop of Henle?
As the filtrate enters the ascending limb of the loop of Henle, the tube becomes impermeable to water and ions are pumped into the interstitium. This creates a gradient of higher ion concentration in the medulla and dilutes the filtrate.
How is water reabsorbed in the loop of Henle?
Water present in the filtrate in the papillary duct flows through aquaporin channels out of the duct, moving passively down its concentration gradient. This process reabsorbs water and creates a concentrated urine for excretion.
Where is calcium absorbed in the nephron?
Proximal tubules
Calcium absorption takes place throughout the nephron. Proximal tubules, thick ascend- ing limbs of Henle’s loop, and distal tubules are the major sites of calcium absorption.
Why is water reabsorbed in the loop of Henle?
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.
How much calcium is reabsorbed in the loop of Henle?
No reabsorption of calcium occurs within the thin segment of the loop of Henle. The cortical segments of the loop of Henle reabsorb about 20% of the initially filtered load of calcium. Approximately 10% of the filtered calcium is reabsorbed in the distal convoluted tubule, with another 3%–10% of filtered calcium reabsorbed in the connecting tubule.
Why is the ascending loop of Henle function impermeable to water?
The ascending loop of Henle function is impermeable to water. In this, sodium chloride is transported from a thick portion of the ascending limb without accompanying water so an osmotic gradient of approximately 200 mosm/kg is generated.
How is magnesium absorbed in the thick ascending limb of Henle?
In the model of magnesium absorption by thick ascending limb of Henle, 40%–70% of filtered magnesium is absorbed in the thick ascending limb by a paracellular pathway, mostly enhanced by lumen-positive transepithelial voltage. The apical Na-K-2Cl cotransporter mediates apical absorption of Na, K, and Cl.
Is there any net potassium reabsorption in the loop Henle?
There is net potassium reabsorption in the loop Henle. The procedure to transport potassium in Henle’s loop is quite complex. Here the potassium is concentrated in the fluid passing through the descending loop of Henle to such an extent that the concentration in the fluid at the papilla is ten times higher than plasma.