Question

Explain the structure of Nephron and mechanism of its working.

Hint:

The nephron's ability to reabsorb water and salts and secrete waste is essential for the body's fluid and electrolyte balance.

Answer 1

The nephron is the functional unit of the kidney, responsible for the filtration of blood and the formation of urine. It is composed of several parts that work together to filter blood and eliminate waste products. The structure of a nephron consists of:
1. Renal Corpuscle:
The renal corpuscle consists of two parts:
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Bowman's Capsule: A cup-shaped structure that encloses the glomerulus.
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Glomerulus: A network of capillaries where blood filtration occurs. Blood enters the glomerulus via the afferent arteriole and is filtered into the Bowman's capsule.
2. Proximal Convoluted Tubule (PCT):
The filtrate from the Bowman's capsule passes into the PCT, where a large amount of reabsorption occurs. Important substances like glucose, amino acids, and ions are reabsorbed back into the blood.
3. Loop of Henle:
The loop of Henle is responsible for the concentration of urine. It has a descending limb that allows water reabsorption and an ascending limb that allows ion reabsorption.
4. Distal Convoluted Tubule (DCT):
The DCT further adjusts the composition of the filtrate. It is involved in the reabsorption of sodium and water, as well as the secretion of potassium and hydrogen ions.
5. Collecting Duct:
The collecting duct collects the filtrate from several nephrons. It plays a key role in the regulation of water and electrolyte balance, influenced by hormones like ADH (Antidiuretic Hormone).
Mechanism of Working:
1. Blood is filtered in the glomerulus under high pressure. Water, salts, glucose, and urea pass into the Bowman's capsule, forming the glomerular filtrate.
2. The filtrate then moves through the PCT, where essential substances are reabsorbed.
3. As the filtrate passes through the loop of Henle, water and salts are reabsorbed to create concentrated urine.
4. In the DCT, additional reabsorption of sodium and water occurs, and waste products like potassium are secreted into the filtrate.
5. The final filtrate enters the collecting duct, where water reabsorption is regulated to form urine, which is eventually excreted.
Conclusion:
The nephron performs blood filtration, reabsorption of useful substances, secretion of waste, and regulation of water and electrolyte balance, playing a key role in maintaining homeostasis.