Question

The figure shows a diagrammatic view of human respiratory system with labels A, B, C and D. Select the option which gives correct identification and/or characteristic.

• A. C - Alveoli - Thin-walled vascular bag-like structures for exchange of gases.
• B. D - Lower end of lungs - Diaphragm pulls it down during inspiration.
• C. A - Trachea - Long tube supported by complete cartilaginous rings for conducting inspired air.
• D. B - Pleural membrane - Surround ribs on both sides to provide cushion against rubbing.

Answer 1

The correct option is A C - Alveoli - Thin-walled vascular bag-like structures for exchange of gases.

In the given diagram, A represents the trachea. It is supported by incomplete cartilaginous rings (the option mentions this as complete cartilaginous rings) that prevent its collapse during inspiration. B marks the pleural membrane, which is the double-layered membrane covering the lungs (and not surrounding the ribs, as the option mentions). C represents the alveoli which are thin-walled sacs having an extensive network of capillaries for gaseous exchange. D marks the diaphragm itself, which is the dome-shaped muscular structure that plays an important role in breathing.