AP BIOLOGY

Detailed explanation-1: -This increases the size of the thoracic cavity and decreases the pressure inside. As a result, air rushes in and fills the lungs. The second phase is called expiration, or exhaling. When the lungs exhale, the diaphragm relaxes, and the volume of the thoracic cavity decreases, while the pressure within it increases.

Detailed explanation-2: -[1] Increasing the volume of the thoracic cavity causes a decrease in the intrathoracic pressure and an influx of air. Meanwhile, decreasing the volume of the thoracic cavity generally occurs by the relaxation of the muscles of inspiration, which causes an increase in intrathoracic pressure and results in exhalation.

Detailed explanation-3: -Breathing in This increases the space in your chest cavity, and your lungs expand into it. The muscles between your ribs also help enlarge the chest cavity. They contract to pull your rib cage both upward and outward when you inhale. As your lungs expand, air is sucked in through your nose or mouth.