1.

Inspiratory muscles and expiratory muscles play very important role in respiratory process.

Answer»

The contraction of the external inter costal muscles and diaphragm leads to increase in volume of thoracic cavity. An increase in pulmonary volume decreases the intra-pulmonary pressure to less than atmospheric pressure. Thus forcing air into the lungs from outside. This is inspiration. Relaxation of the diaphragm and the inter-costal muscles returns the diaphragm and the sternum to their normal positions and reduce the thoracic volume and thereby the pulmonary volume. This lead to an increase in intra-pulmonary pressure in comparison to the atmospheric pressure. This causes expiration.



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