Dominic Stone
The abdominal muscles, commonly known as the abs, are a set of muscles that line the walls of the abdomen. They are located between the rib cage and the pelvis at the front of the body. The abdominal muscles have several important functions, including holding internal organs in place, supporting the trunk, and enabling movement. The five main abdominal muscles are the pyramidalis, rectus abdominis, external obliques, internal obliques, and transversus abdominis. These muscles can be injured through strain or hernias, which can be prevented through regular stretching, warming up, and cooling down.
| Characteristics | Values |
|---|---|
| Number of abdominal muscles | 5 |
| Types of abdominal muscles | Anterolateral; Posterior |
| Anterolateral muscles | External oblique, internal oblique, transversus abdominis, rectus abdominis, pyramidalis |
| Posterior muscles | Psoas major, quadratus lumborum |
| Location | Between the rib cage and pelvis |
| Function | Hold organs in place, support the trunk, allow movement, maintain posture, stabilize the trunk, maintain internal abdominal pressure, support the spine and pelvis |
| Appearance | "Six-pack" appearance due to bumps or bulges when contracting |
| Blood supply | Inferior epigastric artery and vein, superior epigastric artery, intercostal arteries |
| Nerve supply | Thoraco-abdominal nerves, thoracic nerves |
| Injuries | Abdominal muscle strain, hernia |
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What You'll Learn
- Rectus abdominis: a pair of muscles that run down the abdomen, often forming a ''six-pack'
- External obliques: the outermost muscles of the abdominal wall, allowing the trunk to twist
- Internal obliques: paired muscles lying on either side of the abdomen, deeper than the external obliques
- Transversus abdominis: the deepest abdominal muscle, helping to stabilise the trunk
- Pyramidalis: a small, vertical muscle at the base of the pubic bone, present in 80% of people
Rectus abdominis: a pair of muscles that run down the abdomen, often forming a ''six-pack'
The rectus abdominis muscle, also known as the "abdominal muscle" or simply "abs", is a pair of segmented muscles that run down the front of the abdomen. They are skeletal muscles, and their main function is to move the body between the rib cage and the pelvis. They also hold the internal organs in place and keep the body stable during movement.
The rectus abdominis muscles extend from the pubic symphysis, pubic crest, and pubic tubercle at the bottom to the xiphoid process and the 5th to 7th costal cartilages of the ribs at the top. They are separated at the midline by a band of dense connective tissue called the linea alba. Each rectus abdominis muscle is also traversed by bands of connective tissue called the tendinous intersections, which divide them into distinct muscle bellies.
The rectus abdominis muscles have three horizontal tendons running across their front, creating the characteristic "six-pack" appearance when the abdominal muscles are well-defined. This appearance is due to low belly fat, which allows the muscle detail to show through. However, it is important to note that achieving this appearance is not simply a matter of reducing body fat, but also involves proper diet and exercise.
The rectus abdominis muscles are susceptible to strains and injuries, which can cause abdominal pain and difficulty with trunk movements. Strains can occur due to overstretching, overuse, or violent twisting of the trunk. In severe cases, a muscle strain can result in a rupture of the muscle from its attachment. It is important to take precautions to prevent injury, such as warming up before exercise and maintaining good form during sports or other physical activities.
To strengthen the rectus abdominis muscles, specific exercises can be performed, such as lying on the floor with bent knees and sliding the hands towards the knees while raising the head and shoulders off the ground. This type of targeted exercise can help to improve core strength and stability, contributing to overall fitness and health.
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External obliques: the outermost muscles of the abdominal wall, allowing the trunk to twist
The external obliques are a pair of muscles, one on each side of the rectus abdominis. They are the largest and outermost of the three flat abdominal muscles of the lateral anterior abdomen. They are situated on the lateral and anterior parts of the abdomen, extending from the lower half of the ribs around and down to the pelvis. They are broad, thin, and irregularly quadrilateral, with their muscular portion occupying the side and their aponeurosis occupying the anterior wall of the abdomen.
The external obliques are the largest of the flat muscles and sit at the bottom of the stack. They run from the sides of the body toward the middle. The external obliques allow the trunk to twist from side to side, but to the opposite side of whichever external oblique is contracting. For example, the right external oblique contracts to turn the body to the left.
The external obliques work together with the internal obliques and rectus abdominis to flex the trunk anteriorly. This activity also increases the tone of the abdominal wall and positive intra-abdominal pressure, which is useful in various physiological processes such as forced exhalation, micturition, defecation, and labour. Bilateral contraction of the external obliques, along with the rectus abdominis and internal oblique, flexes the trunk by drawing the pubis towards the xiphoid, as in crunches or sit-ups.
The external oblique also functions to pull the chest downwards and compress the abdominal cavity, which increases intra-abdominal pressure. It performs ipsilateral (same-side) side-bending and contralateral (opposite-side) rotation: the right external oblique bends to the right and rotates to the left, and vice versa.
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Internal obliques: paired muscles lying on either side of the abdomen, deeper than the external obliques
The internal obliques are a pair of muscles lying on either side of the abdomen, deeper than the external obliques but outside the transversus abdominis. They are thinner and smaller than the external obliques. The internal obliques arise from the hip bone and attach to the lower six ribs. They flank the rectus abdominis and are located just inside the hip bones.
The internal obliques work with the external obliques to allow the trunk to twist and turn. They operate in the opposite way to the external obliques. For example, twisting the trunk to the left requires the left internal oblique and the right external oblique to contract together. The internal obliques are part of the anterolateral abdominal muscles, which also include the external obliques, transversus abdominis, rectus abdominis, and pyramidalis.
The abdominal muscles as a whole have many important functions, including holding organs in place, supporting the trunk, and helping with movement. They maintain a uniform pressure inside the abdomen, which helps the stomach, intestines, pancreas, liver, gallbladder, and other organs hold their positions. By contracting, the abdominal muscles can increase the pressure inside the abdomen, aiding in passing urine and stool and during childbirth. They also help maintain posture and provide core support by supporting the spine and pelvis.
Abdominal muscles consist of three flat muscles (two obliques and the transversus abdominis) and two vertical muscles (the rectus abdominis and pyramidalis). The rectus abdominis is a pair of muscles that run down either side of the middle of the abdomen from the ribs to the front of the pelvis. They are divided into two segments by a muscle called the linea alba. The rectus abdominis holds the internal organs in place and keeps the body stable during movement.
Abdominal muscle strains are common and can be caused by overstretching, overuse, or violent twisting of the trunk. Strains can range from minor tears in the muscle fibres to severe pulls that detach the muscle. Hernias are another common condition affecting the abdominal muscles, where a bulge forms due to a weakness or gap in the muscles.
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Transversus abdominis: the deepest abdominal muscle, helping to stabilise the trunk
The transversus abdominis is the deepest abdominal muscle, and it helps to stabilise the trunk. It is one of the five main abdominal muscles, along with the pyramidalis, rectus abdominus, external obliques, and internal obliques. These muscles support the trunk, allow movement, and hold organs in place.
The transversus abdominis is a broad paired muscular sheet found on the lateral sides of the abdominal wall. It is layered on top of the internal obliques, and together with the external abdominal oblique and the internal abdominal oblique, it comprises the lateral abdominal muscles. The transversus abdominis is innervated by the lower intercostal nerves, the iliohypogastric nerve, and the ilioinguinal nerve.
The transversus abdominis helps to stabilise the trunk and maintain internal abdominal pressure. It also serves to compress and retain the contents of the abdomen, providing thoracic and pelvic stability. Additionally, it assists in exhalation, contracting during the exhalation phase of respiration to force air out of the thorax.
The transversus abdominis is important for maintaining normal abdominal tension and increasing intra-abdominal pressure. It has several origin points, including the lateral one-third of the superior surface of the inguinal ligament and the anterior two-thirds of the inner lip of the iliac crest. From these origin points, the transversus abdominis fibres course horizontally over the lateral abdominal wall towards the midline.
Training the transversus abdominis can help to improve core stability and protect against back injury or strain during movement or normal posture. Exercises such as Pilates and using a stability ball can help to train this muscle group. However, it is important to be careful when choosing abdominal exercises and to consult a qualified fitness instructor or healthcare professional for guidance.
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Pyramidalis: a small, vertical muscle at the base of the pubic bone, present in 80% of people
The abdominal muscles, or abs, are strong bands of muscles lining the walls of the abdomen. They have many important functions, from holding internal organs in place to supporting the body during movement.
The abdominal muscles are also known as the core muscles, as they help protect the spine and keep the body stable and balanced. They are located between the ribcage and the pelvis on the front of the body.
There are five main abdominal muscles: the pyramidalis, rectus abdominis, external obliques, internal obliques, and transversus abdominis. The rectus abdominis is the muscle that forms the characteristic "six-pack" when someone has a trim, fit abdomen.
The pyramidalis muscle is a small, triangular-shaped vertical muscle at the base of the pubic bone. It sits in front of the rectus abdominis and attaches to the linea alba. The pyramidalis muscle is present in 80% of people and is involved in maintaining internal pressure in the abdomen. When the pyramidalis contracts, it tenses the linea alba, contracting with other abdominal muscles to increase positive abdominal pressure. This pressure regulation is essential for various bodily functions, such as breathing, coughing, and childbirth.
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Frequently asked questions
The abdominal muscles, also known as the abs, are a pair of segmented skeletal muscles on the ventral aspect of a person's abdomen. They are located between the ribcage and the pelvis at the front of the body.
There are five main abdominal muscles: pyramidalis, rectus abdominus, external obliques, internal obliques, and transversus abdominis.
The abdominal muscles have many functions, including holding organs in place, supporting the body during movement, maintaining posture, and providing core support. They also help with breathing, coughing, vomiting, defecating, and urination.
There are various exercises that can be performed to strengthen the abdominal muscles, including rectus exercises, oblique exercises, and Pilates. It is important to learn proper form and technique to prevent injury.
