Read the given statements and select the correct option.Statement 1: T...
The counter current mechanism in loop of Henle and vasa recta, helps in maintaining an increasing osmolarity of the interstitial fluid i.e. form 300 mOsmoL-1 in the cortex is about 1200 mOsmolL-1 in the inner medulla. This gradient is mainly caused by NaCl and urea. This gradient thus helps in easy reabsorption of water from the filtrate in the collecting duct so as to produce hyperosmotic urine.
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Read the given statements and select the correct option.Statement 1: T...
Statement 1: The final reabsorption of water from the urine into the blood occurs through the collecting duct of a mammalian nephron resulting in the production of hyperosmotic urine.
Statement 2: The loop of Henle creates a sodium gradient in the interstitial fluid.
Explanation:
1. Final reabsorption of water
- In the mammalian nephron, the process of urine formation starts in the renal corpuscle, where filtrate is formed by the glomerulus and Bowman's capsule.
- This filtrate then flows through the proximal convoluted tubule (PCT), where a significant amount of water and solutes are reabsorbed back into the blood.
- The fluid then enters the loop of Henle, which is a U-shaped structure consisting of a descending limb and an ascending limb.
- As the fluid flows down the descending limb, it becomes more concentrated due to the reabsorption of water.
- The loop of Henle plays a crucial role in creating a concentration gradient in the medulla of the kidney.
2. Loop of Henle and sodium gradient
- The descending limb of the loop of Henle is permeable to water but not to solutes, while the ascending limb is impermeable to water but allows the reabsorption of solutes, particularly sodium ions.
- As the fluid flows up the ascending limb, sodium ions are actively transported out of the tubule and into the interstitial fluid.
- This creates a concentration gradient of sodium ions in the interstitial fluid, with higher concentrations in the medulla compared to the cortex.
- The high concentration of sodium ions in the interstitial fluid allows for the reabsorption of water from the collecting duct.
- The collecting duct, which is the final part of the nephron, is permeable to water and can reabsorb water from the urine into the blood.
- This reabsorption of water from the collecting duct occurs passively due to the osmotic gradient created by the high concentration of sodium ions in the interstitial fluid.
- As a result, the urine becomes more concentrated (hyperosmotic) as it passes through the collecting duct.
Conclusion:
Both Statement 1 and Statement 2 are correct, and Statement 2 provides the correct explanation for Statement 1. The loop of Henle plays a crucial role in creating a sodium gradient in the interstitial fluid, which allows for the reabsorption of water from the collecting duct and the production of hyperosmotic urine.
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