Intercostal Muscles: How They Power Breathing - Anatomy & Function

The intercostals are a group of muscles located between the ribs.

There are two sets of intercostal muscles:

- The external intercostal muscles are located between the ribs and run in a downward and forward direction.

- The internal intercostal muscles are located deep to the external intercostals and run in an upward and backward direction.

During normal, quiet breathing, the intercostals work together to expand and contract the chest cavity, allowing for the lungs to fill and empty with air. The external intercostal muscles are responsible for inspiration (inhaling), while the internal intercostal muscles are responsible for expiration (exhaling).

Inspiration: During inspiration, the external intercostal muscles contract, pulling the ribs upward and outward, which expands the chest cavity. This creates negative pressure within the chest cavity, which draws air into the lungs.

Expiration: During expiration, the external intercostal muscles relax, and the internal intercostal muscles contract. This pulls the ribs downward and inward, reducing the volume of the chest cavity and pushing air out of the lungs.

In addition to their role in normal breathing, the intercostals also assist with coughing, sneezing, and singing.