Breathing is essential for the various biological functions that occur in the body. Specific muscles are used during conscious and unconscious breathing and function 24 hours a day. These muscles work together to inhale and exhale air from the lungs.
Features
The diaphragm is a dome shaped muscle located under the lungs in the thoracic cavity. Eleven pairs of external intercostals extend from rib to rib in a downward direction and11 pairs of internal intercostals extend from rib to rib but are deeper than the external intercostals. The abdominal muscles also aid in breathing.
Function
For a typical breath the diaphragm flattens during contraction and increases the volume of the thoracic cage. The volume increase creates a partial vacuum that brings air into the lungs. The external intercostals promote inhalation by lifting the rib cage upward and outward. Air is exhaled from the lungs when these muscles relax . The internal intercostals support forced expiration such that used when blowing up a balloon. Abdominal muscles assist forced expiration by increasing the pressure put on the diaphragm.
Breathing During Exercise
During exercise, breathing is assisted by accessory inspiratory muscles, which include the sternocleidomastoid, scalene and trapezius muscles. These muscles lift the ribs and clavicles vertically, allowing for large increases in air volume during exercise.
Control
The act of breathing is controlled by a respiratory center in the brain. The center receives hormonal and neural inputs from sources internal and external to the body. The brain uses this information to regulate breathing frequency and strength and maintain optimal function. The respiratory center allows breathing to occur unconsciously and effectively.
Considerations
Skeletal muscle strengthens with exercise. Throughout a training program the muscles used for breathing will improve and become more efficient. Muscles used during relaxed breathing work at all times but the accessory inspiratory muscles assist with breathing during exercise.
References
- "Exercise Physiology"; George A. Brooks, Thomas D. Fahey and Kenneth M. Baldwin; 2005
- "Anatomy and Physiology"; Kenneth S. Saladin; 2004
