The size of the chest cavity increases during inhalation. Class 10 Science (MCQ) Answer

The size of the chest cavity increases during inhalation.

Answer: Verified

Hint: The lungs are the organs of respiration. Respiration occurs in two stages: inhalation and exhalation. Inhalation involves breathing in oxygen, while exhalation expels carbon dioxide, a metabolic waste product.

Complete Answer: The thoracic cavity (chest cavity) helps maintain negative pressure to keep the airways of the lungs open. During inhalation, lung volume increases as the diaphragm and intercostal muscles contract, expanding the chest cavity. The diaphragm moves downward and the lungs expand due to their elasticity. These opposing forces help fill and empty the lungs.

During exhalation, the intercostal muscles and diaphragm relax, decreasing the chest cavity’s volume as the diaphragm moves back upward. This change in pressure forces air out of the lungs.

Therefore, option (A) is correct.

Note: When air is inhaled, the rib cage moves up and outward. When air is exhaled, it moves down and inward. Gas exchange occurs in the alveoli, tiny sacs in the lungs surrounded by capillaries.