A human adult at rest, on an average breathes about 12-20 times per minute i.e. 28800 times per day. The mechanism of breathing in human beings involves two processes : Inhalation and Exhalation.
1. Inhalation : When the muscular diaphragm of the body relaxes, volume of the thoracic cavity increases and air pressure inside the cavity decreases. The air from outside enters the lungs through the nostrils
and the alveolar sacs are filled with air rich in oxygen.
2. Exhalation : When the diaphragm contracts or becomes convex, the thoracic cavity decreases in volume. Lungs come to their original size, forcing the air outside the lungs through the same path but in the
opposite direction.
1. Inhalation : When the muscular diaphragm of the body relaxes, volume of the thoracic cavity increases and air pressure inside the cavity decreases. The air from outside enters the lungs through the nostrils
and the alveolar sacs are filled with air rich in oxygen.
2. Exhalation : When the diaphragm contracts or becomes convex, the thoracic cavity decreases in volume. Lungs come to their original size, forcing the air outside the lungs through the same path but in the
opposite direction.
