Muscles Involved in Breathing: Inhalation & Exhalation Explained

During inhalation, the following muscles contract:

1. Diaphragm: The diaphragm is the primary muscle of inspiration. It is a large, dome-shaped muscle located at the bottom of the thoracic cavity. When the diaphragm contracts, it pulls downward and forward, increasing the volume of the thoracic cavity and lungs, causing air to flow in.

2. External intercostal muscles: The external intercostal muscles are located between the ribs. When they contract, they pull the ribs upward and outward, further increasing the volume of the thoracic cavity and lungs.

During exhalation, the following muscles contract:

1. Internal intercostal muscles: The internal intercostal muscles are located between the ribs, deep to the external intercostal muscles. When they contract, they pull the ribs downward and inward, decreasing the volume of the thoracic cavity and lungs, causing air to flow out.

2. Abdominal muscles: The abdominal muscles include the rectus abdominis, obliques, and transversus abdominis. When they contract, they pull the abdominal wall inward and upward, compressing the abdominal organs and pushing the diaphragm upward, further decreasing the volume of the thoracic cavity and lungs and forcing air out of the lungs.