What muscles do you use to breathe?

Answer 1

In total, there are eleven muscles that control or contribute to the act of respiration.

The main muscle for respiratory inhalation is the diaphragm, which is located deep within the abdominal cavity. When the diaphragm contracts it opens more space within the chest which allows the lungs to fill with air. This process would not be entirely possible if the lungs did not have room to expand. The sternocleidomastoid (SCM), external intercostals, and the internal intercostals (the interchondral portion) all work to expand the rib cage and provide the space needed for the lungs to expand and fill. During exercise, greater volumes of air are usually needed, so there is a greater need for space within the ventral cavity (the thoracic and abdominopelvic cavities combined). Smaller, lesser known muscles assist in lifting the the first two ribs (the scalenes), and still more help to expand the rib cage (levator costarum and serratus posterior).

For respiratory exhalation, the diaphragm relaxes, pushing up on the lungs to expel the used air. An absent breath (the unconscious breaths taken during regular activity) does not always use all of the muscles that are present in a conscious breath. For a conscious breath many muscles work together to help stabilize the ventral cavity. To exhale consciously, internal intercostals(excluding the interchondral portion), external abdominal oblique, internal abdominal oblique, transverse abdominis, and rectus abdominis are all used.

The diaphragm contracts down, opening the ventral cavity for the lungs to expand. Considering this action occurs in both the frontal and and midsagittal planes, the plane of motion for the diaphragm can properly be labeled as oblique.

The sternocleidomastoid (SCM), works in assisting the lifting of the clavicle through lateral flexion to the ipsilateral (same) side. Since this is lateral flexion, the plane of motion is frontal, and it is rather easy to imagine these two powerful muscles contracting up and down in this manner.

The external and internal intercostals work together to elevate both the ribs and the cartilage of ribs one through four. The internal intercostals work a little harder however, as they work during exhalation, as well, depressing all of the ribs. For the external intercostals' act in elevating the ribs, the muscles rise along both the frontal and the midsagittal planes, creating an oblique plane of motion. For the internal intercostalis' work in elevation and depression they rise and fall simply up and down the frontal plane of motion.

Scalene muscles are truly divided into anterior, medius and posterior scalenes; all three of which act upon the first and second ribs during respiratory inhalation. While Scalenus anterior and scalenus medius work to elevate the first rib, scalenus posterior alone is left to elevate the second rib. As this action is a simple lift, the frontal plane of motion as well as the midsagittal plane come into play, creating the oblique plane of motion once again.

The external abdominal oblique muscles work similarly to the SCM in that their motions are (lumbar) lateral flexion on the ipsilateral side. The plane of motion is frontal and an image of the muscles contracting to help draw the ribs back into place is quite easy to imagine. Unlike the SCM however, the external abdominal obliques can work at various angles. Also in their repertoire is simple lumbar flexion, which adds the sagittal plane to their planes of motion.

Internal abdominal oblique, like their counterparts (external abdominal obliques), have flexion in more than one pattern. They can cause lumbar flexion as well as lumbar lateral flexion to their ipsilateral sides, placing their motions in sagittal and frontal planes of motion respectively.

The transverse abdominis playsa vital role in forced expiration by pulling the abdominal wall inward (which is to say "sucks in the stomach"). When one pictures the transverse as a band around the middle, knowing this action takes place on the transverse plane of motion is able to be pictured vividly.

The rectus abdominis, a muscle well known to all of us, plays an important role in our every day motions, no matter what they may be. A proper breath starts in the abdomen and rises up through the thoracic cavity until ending at the top of the chest, then following this path in reverse for exhalation. It should come as little or no surprise that the rectus abdominis, then, plays an important role in both lumbar flexion and lateral lumbar flexion that helps in controlled breathing. For the lumbar flexion, the plane of motion is sagittal and for the ipsilateral flexion, the plane of motion changes to the frontal plane.

Due to the minimal roles of the Levator Costarum and the Serratus Posterior, they have been left out of this response.