Explain the mechanism of inspiration?

Hint: Breathing has two phases:
1) Inspiration means inhalation.
2) Expiration means exhalation.

Complete Answer:
Inspiration is a process of breathing in and is vital for supplying oxygen to tissues and eliminating carbon dioxide from the body. Inspiration occurs by contacting the muscles such as Diaphragm.

MECHANISM OF INSPIRATION:
- It is an active process which takes place via contraction of inspiratory muscles.
- This contraction of inspiratory muscles expands the thoracic cavity which leads to decreased intrapleural pressure. This drop in intrapleural pressure leads to expansion of lungs.
- After the expansion, intrapulmonary pressure decreases to subatmospheric level which causes air from the atmosphere to be sucked into the lungs.
- Muscles for inspiration are: Diaphragm and external intercostals muscle.
- The Diaphragm is the main muscle of inspiration, which is called skeletal muscle.

Contraction of diaphragm results in inflation of the lungs and also the expansion of thoracic cavity into two ways:
- The shape of the diaphragm is dome and it is attached to the lower six ribs. When diaphragm contracts, the abdominal contents are pushed downward which causes enlargement of thoracic cavity into rosto-caudant extent.
- Contraction also pushes the rib cage outward which also enlarges the thoracic cavity in its antero-posterior and lateral planes.

Accessory muscles of inspiration:
1) Scalenes
2) Sternocleidomastoids
3) Neck and back muscles.

Note: The muscles of respiration are those muscles that help in inhalation and exhalation.