MECHANISM OF BREATHING NCERT NEET
Channel: ISHTA’s BIO ACADEMY
Date: 22/04/2021

Breathing involves two stages : inspiration during which atmospheric
air is drawn in and expiration by which the alveolar air is released out.
The movement of air into and out of the lungs is carried out by creating a
pressure gradient between the lungs and the atmosphere. 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 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 intercostals between the ribs, help in generation of such gradients.
Inspiration is initiated by the contraction of diaphragm which increases
the volume of thoracic chamber in the antero-posterior axis.