Dominic Stone
The abdominal muscles are strong bands of muscles lining the walls of the abdomen, which is the trunk of the body. They are located between the ribcage and the pelvis on the front of the body. The abdominal muscles have several important roles, including supporting the trunk, enabling movement, and holding the organs in place. They also help maintain intra-abdominal pressure, which is critical for bodily functions such as sneezing, coughing, vomiting, and defecating.
| Characteristics | Values |
|---|---|
| Location | Between the ribs and the pelvis |
| Composition | 4 or 5 pairs of muscles |
| Muscle Types | Rectus Abdominis |
| External Obliques | |
| Internal Obliques | |
| Transversus Abdominis | |
| Pyramidalis | |
| Function | Support the trunk |
| Allow movement | |
| Hold organs in place | |
| Protect the spine |
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What You'll Learn
- The rectus abdominis is the large muscle in the mid-section of the abdomen
- External oblique muscles allow the trunk to twist from side to side
- Internal oblique muscles are located just inside the hipbones
- Transversus abdominis is the deepest muscle layer
- The pyramidalis is a small, triangular muscle at the base of the pubic bone
The rectus abdominis is the large muscle in the mid-section of the abdomen
The rectus abdominis is a long, flat muscle that extends along the whole length of the abdomen. It is commonly referred to as the "abs muscle" or "six-pack". It is the top layer of the abdominal muscles, and it is separated from its fellow on the opposite side by the linea alba, a connective tissue. The rectus abdominis is flanked by the internal oblique muscles, which are located just inside the hipbones.
The rectus abdominis is an important postural muscle, responsible for flexing the spinal column and lumbar spine. It also tenses the anterior wall of the abdomen and assists in compressing the contents of the abdomen. The muscle is innervated by the thoraco-abdominal nerves, which are continuations of the T7-T11 intercostal nerves. The sensory supply is from the 7-12 thoracic nerves.
The rectus abdominis has many sources of arterial blood supply, including the inferior and superior epigastric arteries. It is attached by two tendons: the larger one is attached to the pubic crest, and the smaller, medial tendon is attached to the pubic symphysis. The fibres of the rectus abdominis extend vertically superiorly and insert into the xiphoid process of the sternum and the costal cartilages of the 5th, 6th, and 7th ribs.
The rectus abdominis is a paired muscle that runs vertically, on either side of the linea alba, on the anterior surface of the abdominal wall. It is similar in most vertebrates. The abdominal muscles, including the rectus abdominis, support the trunk, allow movement, and hold organs in place. They also help to keep the body stable and balanced, protecting the spine.
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External oblique muscles allow the trunk to twist from side to side
The abdominal muscles are the muscles forming the abdominal walls, which connect the thorax and pelvis. They support the trunk, allowing movement, and hold organs in place. The deep abdominal muscles, together with the back muscles, make up the core muscles. They help protect the spine and keep the body stable and balanced.
The external oblique muscles are one of the outermost abdominal muscles. They extend from the lower half of the ribs around and down to the pelvis. They cover the sides of the abdominal area, sitting on the top surface of the abdomen, right below the subcutaneous fat and skin. They are the largest and most superficial of the flat muscles.
The external oblique muscles work in conjunction with the internal oblique muscles, which are located just inside the hipbones. They operate in opposite ways. For example, twisting the trunk to the left requires the left side internal oblique and the right side external oblique to contract together.
The external abdominal oblique muscles, in particular, cause ipsilateral lateral flexion of the trunk and contralateral rotation of the trunk when they contract unilaterally. When contracting bilaterally, the external oblique muscles work together with the internal oblique and rectus abdominis to flex the trunk anteriorly. This activity increases the tone of the abdominal wall and positive intra-abdominal pressure, which is a part of various physiological processes such as forced exhalation, micturition, defecation, and labor.
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Internal oblique muscles are located just inside the hipbones
The abdominal muscles are the muscles that form the abdominal walls, connecting the thorax and pelvis. They support the trunk, allow movement, and hold organs in place. There are five main abdominal muscles: pyramidalis, rectus abdominis, external obliques, internal obliques, and transversus abdominis.
The internal oblique muscles play a crucial role in respiration. They act as antagonists to the diaphragm, helping to reduce the volume of the chest cavity during exhalation. When the diaphragm contracts, it pulls down the lower wall of the chest cavity, increasing the volume of the lungs, which then fill with air. Conversely, when the internal oblique muscles contract, they compress the organs of the abdomen, pushing them upwards into the diaphragm. This causes the diaphragm to intrude back into the chest cavity, reducing the volume of the lungs and facilitating exhalation.
The internal oblique muscles also work in conjunction with the external oblique muscles to achieve torsional movement of the trunk. For example, when the torso flexes and rotates to bring the left shoulder towards the right hip, the right internal oblique and the left external oblique contract simultaneously. This coordination between the internal and external oblique muscles allows for smooth and controlled movements of the trunk.
The internal oblique muscles are essential for maintaining core stability and supporting the spine. They help to keep the body stable and balanced, protecting the spine from injury and hyperextension. By working in harmony with other abdominal muscles, the internal obliques contribute to the overall stability and movement of the torso.
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Transversus abdominis is the deepest muscle layer
The abdominal muscles form the abdominal walls, connecting the thorax and pelvis. They support the trunk, allow movement, and hold organs in place by regulating internal abdominal pressure. The deep abdominal muscles, together with the intrinsic back muscles, make up the core muscles.
Transversus abdominis has several origin points:
- Lateral one-third of the superior surface of the inguinal ligament and the associated iliac fascia
- Anterior two-thirds of the inner lip of the iliac crest
- Thoracolumbar fascia between the iliac crest and the 12th rib
- Internal aspects of the lower six ribs and their costal cartilages
From their origin points, the transversus abdominis fibres course horizontally over the lateral abdominal wall towards the midline, oriented perpendicular to the linea alba. Transversus abdominis is mainly supplied by the terminal branches of the lower five intercostal nerves and the subcostal nerve, that arise from the lower six thoracic spinal nerves (T7-T12).
Weak transversus abdominis muscles can contribute to low back pain and lumbar instability. A weak transversus abdominis can be identified by toned abdominals above the navel and a bulge below it.
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The pyramidalis is a small, triangular muscle at the base of the pubic bone
The abdominal muscles are the muscles that form the abdominal walls, connecting the thorax and pelvis. They support the trunk, allow movement, and hold organs in place. The abdominal muscles work together with the back muscles to support the spine. The deep abdominal muscles, together with the intrinsic back muscles, make up the core muscles.
The inferior and superior epigastric arteries supply blood to the pyramidalis muscle, and it is innervated by the ventral portion of T12. The pyramidalis muscle is used to determine the midline and location of the linea alba during classical caesarean sections. The linea alba is an anterior, tendinous band that runs vertically along the linea alba, which is located between the right and left abdominal muscles.
The pyramidalis muscle tenses the linea alba, which contributes to a variety of abdominal wall functions. For example, it increases intra-abdominal pressure during labour, forced expiration, and defecation.
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Frequently asked questions
Abdominal muscles are located between the ribcage and the pelvis, at the front of the body. They line the walls of the abdomen, which is the trunk of the body.
The vertical muscles of the anterolateral abdominal wall are the rectus abdominis and the pyramidalis.
The flat muscles of the anterolateral abdominal wall are the external oblique, the internal oblique, and the transversus abdominis.
The deepest muscle layer is the transversus abdominis.
The anterolateral abdominal muscles include the rectus abdominis, the external oblique, the internal oblique, the transversus abdominis, and the pyramidalis.
