Part 5: Short Answer 23. Describe the mechanism of inspiration.

Inspiration, or inhalation, is the process of drawing air into the lungs. It is an active process that involves the contraction of the diaphragm and the external intercostal muscles. The diaphragm, a dome-shaped muscle located at the base of the lungs, contracts and flattens, increasing the vertical dimension of the thoracic cavity. The external intercostal muscles, located between the ribs, contract and pull the rib cage upward and outward, increasing the lateral and anteroposterior dimensions of the thoracic cavity. This expansion of the thoracic cavity decreases the pressure inside the lungs relative to the outside atmosphere. As a result, air is drawn into the lungs through the nose or mouth, down the trachea, and into the bronchi and bronchioles, eventually reaching the alveoli where gas exchange occurs.