Dominic Stone
The abdominal muscles are the muscles forming the abdominal walls, which are the walls of the abdomen (the trunk of the body). They are located between the ribs and the pelvis at the front of the body. There are five main abdominal muscles: pyramidalis, rectus abdominis, external obliques, internal obliques, and transversus abdominis. These muscles, together with the back muscles, make up the core muscles, which help keep the body stable and balanced, as well as protecting the spine. So, what muscles are above the abdominals?
| Characteristics | Values |
|---|---|
| Number of abdominal muscles | 5 |
| Types of abdominal muscles | Rectus Abdominis, External Oblique, Internal Oblique, Transverse Abdominis, and Pyramidalis |
| Function | Hold internal organs in place, support the spine, protect the internal abdominal organs, and allow movement |
| Location | Between the ribs and the pelvis on the front of the body |
| Appearance | "Six-pack abs" |
Explore related products
What You'll Learn
External oblique muscles
The external oblique muscle is one of the outermost abdominal muscles, situated on the lateral and anterior parts of the abdomen. It is broad, thin, and irregularly quadrilateral, with its muscular portion occupying the side and its aponeurosis the anterior wall of the abdomen. The external oblique is the largest of the three flat abdominal muscles of the lateral anterior abdomen. It arises from eight fleshy digitations, each from the external surfaces and inferior borders of the fifth to twelfth ribs (the lower eight ribs). These digitations are arranged in an oblique line, with the upper digitations attached close to the cartilages of the corresponding ribs and the lowest attached to the apex of the cartilage of the last rib.
The external abdominal oblique is a paired muscle located on the lateral sides of the abdominal wall. Along with the internal abdominal oblique and transversus abdominis, it comprises the lateral abdominal muscles. The external oblique muscle is innervated by the anterior rami of the thoracic spinal nerves T7-T12. The intercostal nerves T7-T11 supply the superior-most part of the muscle, while the subcostal nerve (T12) innervates the lower part. The muscle receives sensory innervation from the lumbar plexus, via the iliohypogastric nerve (L1). The upper two-thirds of the external abdominal oblique receives blood supply from the branches of the lower posterior intercostal and subcostal arteries, while the deep circumflex iliac artery supplies the inferior third of the muscle.
The external oblique muscle has several functions, including rotating the trunk to the opposite side of the contracting muscle. For example, the contraction of the right external oblique muscle will turn the body to the left. It also helps to pull the chest downwards, compressing the abdominal cavity and increasing intra-abdominal pressure. This compression can be observed during a Valsalva maneuver. Additionally, the external oblique muscle contributes to ipsilateral (same-side) side-bending and lateral flexion of the trunk on the same side.
The external oblique muscles, along with the rectus abdominis and internal oblique muscles, are involved in flexing the trunk by drawing the pubis towards the xiphoid, as seen in crunches or sit-ups. Strain or injury to the external oblique muscle can be debilitating, impacting even movements that do not directly use the muscle, such as walking or running. Oblique strain is a common injury in baseball, particularly for pitchers and batters.
Angina and Heart Muscle: What's the Connection?
You may want to see also
Explore related products
Internal oblique muscles
The internal oblique muscles are one of the five main abdominal muscles, the others being the pyramidalis, rectus abdominis, external obliques, and transversus abdominis. The internal oblique muscles flank the rectus abdominis and are located just inside the hip bones.
The internal oblique muscles are broad, thin muscular sheets found on the lateral side of the abdomen. They are one of the three layers of the abdominal wall, along with the external abdominal oblique and transversus abdominis. The internal oblique muscles are located deep to the external abdominal oblique and superficial to the transversus abdominis. The direction of their fibres is perpendicular to those of the external abdominal oblique.
The internal oblique muscles have multiple sites of origin, distributed along the anterolateral side of the trunk. According to their origin, the muscle fibres can be divided into the anterior, lateral, and posterior fibres. Anterior fibres arise from a deep structure known as the iliopectineal arch, passing inferomedially and arching over the inguinal canal. They then merge with the tendinous fibres of the transversus abdominis muscle to form the conjoint tendon. Lateral fibres originate from the anterior two-thirds of the iliac crest and then diverge superiorly and medially. They extend into an aponeurosis that contributes to the formation of the rectus sheath and insert at the linea alba. Posterior fibres originate from the posterior end of the iliac crest and the thoracolumbar fascia. They then ascend superolaterally and insert into the inferior borders and tips of the lower three or four ribs and their cartilages.
The internal oblique muscles are important for movements of the trunk, maintaining normal abdominal tension, and increasing intra-abdominal pressure. They contract together with the external oblique muscles of the opposite side to produce a torsional movement of the trunk. For example, the right internal oblique and the left external oblique contract as the torso flexes and rotates to bring the left shoulder towards the right hip. The internal oblique muscles also act as an accessory muscle of respiration, helping to reduce the volume of the chest cavity during exhalation.
Building a Solid Foundation: Understanding Base Muscles
You may want to see also
Explore related products
Transverse abdominis
The transverse abdominis (TVA), also known as the transversus abdominis, transversalis muscle, or the body's natural "corset" muscle, is a deep abdominal muscle and one of the most important core muscles. It is the innermost of the flat muscles of the abdomen, layered below the internal oblique muscle. The transversus abdominis sits transversely (horizontally) around the abdomen, contracting during the exhalation phase of respiration to force air out of the thorax. It also helps compress and retain the contents of the abdomen, providing thoracic and pelvic stability.
The transverse abdominis is involved in stabilising the lower spine and protecting the back during heavy compound movements. It works in tandem with the segmental stabilisers of the spine, such as the multifidi, to increase spine stability and protect against back injury or strain during movement or normal posture. Training this muscle can help decrease back pain, improve pelvic floor function, and aid posture.
The transversus abdominis is the only abdominal muscle in which the muscle fibres run side to side, rather than vertically or horizontally. It plays a role in almost all movements, helping to maintain normal abdominal wall tension and increase intra-abdominal pressure, which supports internal organs and viscera.
The transversus abdominis is also crucial during pregnancy and childbirth, helping to deliver the child. Additionally, strengthening this muscle may result in a "cinching" effect around the waist, contributing to a smaller waist appearance.
Protein's Role in Muscle Recovery and Repair Explained
You may want to see also
Explore related products
Rectus abdominis
The rectus abdominis is a long, flat muscle that extends along the whole length of the front of the abdomen, from the rib cage to the pubic bone. It is separated from its fellow muscle on the opposite side by the linea alba, a connective tissue. The rectus abdominis is part of the abdominal muscles, which consist of five main muscle groups that combine to completely cover the internal organs. These include the transversus abdominis, the deepest muscle layer; the external obliques; the internal obliques; and the pyramidalis. The rectus abdominis is also known as the "abs muscle" and is responsible for forming the "'six-pack' in individuals with low body fat.
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 innervated by the thoracoabdominal nerves, which are continuations of the T7-T11 intercostal nerves. The sensory supply is provided by the 7-12 thoracic nerves. The blood supply to the rectus abdominis comes predominantly from the inferior and superior epigastric arteries, along with contributions from other vessels.
The muscle fibres of the rectus abdominis attach to the costal cartilages of the 5th, 6th, and 7th ribs, and insert into the xiphoid process of the sternum. In some cases, the fibres may extend to the 3rd and 4th ribs, or this slip may be absent. The rectus abdominis is attached inferiorly by two tendons: a larger one connected to the pubic crest and a smaller, medial tendon attached to the pubic symphysis.
The main function of the rectus abdominis is to move the body between the rib cage and the pelvis. It flexes the spinal column and assists in compressing the contents of the abdomen. It also plays a role in respiration, particularly during forceful exhalation, and helps maintain posture. The rectus abdominis works in harmony with other abdominal muscles to control the movement of the spine, pelvis, and rib cage during various activities such as walking, running, and swimming.
Intercostal Muscles: Location and Function Explained
You may want to see also
Explore related products
Pyramidalis
The pyramidalis is a small, triangular muscle that is part of the anterior abdominal wall. It is located at the base of the pubic bone, in front of the rectus abdominis muscle, and is attached to the linea alba. The linea alba is a band of connective tissue that runs down the centre of the abdomen, and the pyramidalis muscle sits just below it.
The pyramidalis muscle is innervated by the subcostal nerve, which is the anterior ramus of spinal nerve T12. The inferior and superior epigastric arteries supply blood to the muscle. The muscle is paired, and the two sides are sometimes of unequal size. It is also often absent on one or both sides, and in some cases, it may extend higher than usual.
The function of the pyramidalis muscle is somewhat vague, but it is thought to tense the linea alba when contracting. It is also used as a surgical landmark in classical caesarean sections to determine the midline and location of the linea alba.
The pyramidalis muscle is a vestigial muscle, which means it is tendinous or reduced in size compared to homologous muscles in other species, or frequently absent within or between populations. Phylogenetically, the pyramidalis muscle is linked to the pouch inside monotremes such as hedgehogs, platypuses, and marsupials such as koalas and kangaroos.
Muscle Milk: Shelf Life and Storage Explained
You may want to see also
Frequently asked questions
The abdominal muscles are the muscles forming the abdominal walls, the abdomen being the portion of the trunk connecting the thorax and pelvis. They support the trunk, allow movement, and hold organs in place by regulating internal abdominal pressure.
There are five main abdominal muscles: pyramidalis, rectus abdominis, external obliques, internal obliques, and transversus abdominis.
The abdominal muscles help protect your spine and keep your body stable and balanced. They also help with breathing, coughing, vomiting, and childbirth.
