Mark the correct pair of muscles involved in the normal breathing in humans.

Options

A. External and internal intercostal mucles
B. Diaphragm and abdominal muscles
C. Diaphragm and external intercostal muscles
D. Diaphragm and intercostal muscles

Answer

D

Explanation

Breathing involves two stages : inspiration during which atmospheric air is drawn in and expiration by which the alveolar air is reeased out. Inspiration can occur if the pressure within the lungs (intra-pulmonary pressure) is less than the atmospheric pressure, i.e, there is a negative pressure in the lungs with respect to atmosperic pressure. Simiarly, expiration lungs with respect to atmospheric pressure. Similarly, expiration takes place when the intra-pulmonary pressure is higher than the atmospheric pressure. The diaphragm and a specialised set of muscles-external and internal intercoastals between the ribs, help in generation of such gradients.