Abdominal muscles


Four distinct pairs of abdominal muscles create the flat anterolateral abdominal wall. These muscles resemble sheets of muscle tissue, flat and in some cases even straight during contraction. The external abdominal oblique, the internal abdominal oblique, transversus abdominis, and the rectus abdominis are the muscles which create the abdominal wall.


The basic functions of these abdominal muscles involve providing structural support for the abdominal cavity as well as providing protection for the internal organs residing within the abdominal walls. These muscles are also available to assist in the process of respiration.

Contraction of the muscles of the abdominal wall usually assists in activities such as protecting and offering the spine extra stability when lifting heavy objects or assisting in the process of defecation.

Childbirth is also assisted via the contraction of the muscles of the abdominal wall. Many movements and activities are aided by smaller, less noticeable contractions of these muscles.

Choosing from the three layered muscles of the lateral abdominal wall, the external abdominal oblique remains the most superficial yet ironically the strongest.


Muscles of the Abdominal Wall
Image: Muscles Of The Abdominal Wall


The fibers of the muscle are directed medially and inferiorly to amplify its contraction. Buried deep to the external abdominal oblique is the internal abdominal oblique muscle. The muscles fibers of the internal oblique are designed to lay at right angles to those of the external oblique, creating a strong structural and functional unison between the two muscles.

The deepest of the muscles of the abdomen is the transversus abdominis. The long fibers of this muscle are put to use across the abdominal wall, laterally.


A large sheath encases the long rectus abdominis in its entirety. This strap-like muscle remains encased in a fibrous sheath created by aponeuroses that comes from the fibers of the other three muscles of the abdominal wall.

Segregated the two rectus abdominins muscles is a band of connective tissue called the linea alba, running the entire midline region of the abdominal wall. The appearance of “abs,” the segmented muscle ripple of a human with good muscle tone and low body fat in the abdominal region, is created by tendons which transect the abdomen horizontally.
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