Explain the role of nostrils in the process of respiration.
Answers
Respiration process involves two steps:
- 1. Inspiration
- 2. Expiration
1. Inspiration:
1. The entry of air into the lungs is called as inspiration or inhalation.
2. It involves:
Contraction of the diaphragm muscles. As a result, it moves downwards, that is, the diaphragm becomes flat.
Contraction of external intercostal muscles & relaxation of internal intercostal muscles. As a result, the ribs move outward & forward that is, anteroventral movement of the ribs. The above changes in the factors cause an increase in the thoracic volume but the thoracic pressure is reduced. Hence, due to less pressure air enters into the lungs.
2. Expiration:
1. The exit of air () from the lungs is called expiration or exhalation.
2. It involves:
Relaxation of the muscles of the diaphragm, As a result, the diaphragm moves upwards & resumes dome shape.
Contraction of internal intercostal muscles and relaxation of external intercostal muscles. As a result, the ribs move inward & backwards i.e. posterior - the dorsal movement of the ribs. The above changes in the factors cause a decrease in the thoracic volume but the thoracic pressure is increased. Hence, due to increased pressure air comes out of the lungs.
Note: The breathing rate in adult human beings is 12 to 20 per minute.
