Science — CBSE Class 10 board question

(a) Diagram of Nephron:

```
Bowman's Capsule
|
Glomerulus (capillary cluster)
|
Proximal Convoluted Tubule (PCT)
|
Loop of Henle
|
Distal Convoluted Tubule (DCT)
|
Collecting Duct
```

(A well-labelled diagram should show: Bowman's capsule, Glomerulus, PCT, Loop of Henle, DCT, and Collecting duct — at least 4 parts labelled.)

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(b) Role of capillary cluster (Glomerulus) inside Bowman's capsule:

The capillary cluster inside the Bowman's capsule is called the glomerulus. Blood is filtered here under high pressure. Water, glucose, amino acids, urea, and salts pass from the blood into the Bowman's capsule as filtrate. This process is called ultrafiltration.

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(c) Selective Reabsorption:

As the filtrate passes through the tubular part of the nephron, useful substances such as glucose, amino acids, salts, and water are reabsorbed back into the blood capillaries surrounding the tubule. This process of absorbing only useful substances (and not waste like urea) back into the blood is called selective reabsorption.

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• The diagram carries most marks in part (a); label at least 4 parts clearly with arrows.
• For (b), the key terms examiners look for are glomerulus, filtration/ultrafiltration, and the substances filtered (glucose, urea, salts, water).
• For (c), stress the word "selective" — not everything is reabsorbed; only useful substances are, while wastes remain in the filtrate. This distinction is what earns marks.