Question

19. Define breathing. Explain the mechanism of breathing in human beings.
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Answer 1

Answer:

Breathing

the process of taking air into and expelling it from the lungs.

Explanation:

The mechanism of breathing involves two main processes: inspiration and expiration. ... Expiration occurs when the diaphragm and the intercostal muscles relax. The contraction or relaxation of muscles around the lungs changes the entire volume of air inside the lungs, and so does the pressure.

Answer 2

Answer:

When we breathe in, the intercostal muscles contract and the ribs are pushed out words and upwards. the diaphragm contracts and moves down. The chest cavity becomes larger and its volume increases and the air crashes into the lungs.During breathing out, the intercostal muscles relax and the ribs move downwards and inwards. The diaphragm is relaxed and moves back. The chest cavity shrinks and its volume decreases. The air containing carbon dioxide is has pushed out of the lungs.