What best describes the biomechanics of breathing?

Breathing involves the coordinated function of the respiratory muscles, the lungs, and the chest cavity. The primary muscles involved in breathing are the diaphragm and the intercostal muscles. The diaphragm is a large dome-shaped muscle that separates the thoracic cavity from the abdominal cavity. The intercostal muscles are located between the ribs and help expand the chest cavity.

When you inhale, the diaphragm contracts and the intercostal muscles pull the ribs upward and outward. This increases the volume of the chest cavity, causing the lungs to expand and air to flow into the lungs. The intrapleural pressure (pressure between the lungs and the chest wall) decreases during inspiration, facilitating lung expansion.

During exhalation, the diaphragm relaxes and the intercostal muscles move downward and inward. This decreases the volume of the chest cavity, causing the lungs to collapse and air to be expelled from the lungs. The intrapleural pressure increases during expiration, helping to expel the air.

The respiratory system also involves the exchange of gases between the lungs and the blood. Oxygen from the inhaled air passes from the lungs into the blood through the alveoli, while carbon dioxide passes from the blood into the lungs to be exhaled.