Question

During inhalation the diaphragm

• A. Releases
• B. Folds
• C. Straightens
• D. Contracts

Answer 1

The correct option is D Contracts

1. 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.
2. The diaphragm and a specialised set of muscles – external and internal intercostals between the ribs, help in generation of such gradients.
3. Inspiration is initiated by the contraction of a diaphragm which increases the volume of the thoracic chamber in the anteroposterior axis.
4. The contraction of external inter-costal muscles lifts up the ribs and the sternum causing an increase in the volume of the thoracic chamber in the dorsoventral axis.
5. The overall increase in the thoracic volume causes a similar increase in pulmonary volume. An increase in pulmonary volume decreases the intrapulmonary pressure to less than the atmospheric pressure which forces the air from outside to move into the lungs,i.e., inspiration. Hence, during inhalation the diaphragm contracts.

So, the correct answer is 'contracts'.