Rectus abdominis | |
---|---|
Details | |
Origin | Crest of pubic |
Insertion | Costal cartilages of ribs 5-7 xiphoid process of sternum |
Artery | Inferior epigastric artery |
Nerve | Segmentally by thoraco-abdominal nerves (T7 to T11) and subcostal (T12) |
Actions | Flexion of the lumbar spine |
Antagonist | Erector spinae |
Identifiers | |
Latin | musculus rectus abdominis |
MeSH | D017568 |
TA98 | A04.5.01.001 |
TA2 | 2357 |
FMA | 9628 |
Anatomical terms of muscle |
The rectus abdominis muscle, (Latin : straight abdominal) also known as the "abdominal muscle" or simply the "abs", is a pair of segmented skeletal muscle on the ventral aspect of a person's abdomen (or "midriff"). The paired muscle is separated at the midline by a band of dense connective tissue called the linea alba, and the connective tissue defining each lateral margin of the rectus abdominus is the linea semilunaris. The muscle extends from the pubic symphysis, pubic crest and pubic tubercle inferiorly, to the xiphoid process and costal cartilages of the 5th–7th ribs superiorly. [1] [2]
The rectus abdominis muscle is contained in the rectus sheath, which consists of the aponeuroses of the lateral abdominal muscles. Each rectus abdominus is traversed by bands of connective tissue called the tendinous intersections, which interrupt it into distinct muscle bellies. In people with low body fat, these muscle bellies can be viewed externally in sets from as few as two to as many as twelve, although six is the most common. [3]
The rectus abdominis is a very long flat muscle, which extends along the whole length of the front of the abdomen, and is separated from its fellow of the opposite side by the linea alba. Tendinous intersections (intersectiones tendineae) further subdivide each rectus abdominis muscle into a series of smaller muscle bellies. Tensing of the rectus abdominis causes the muscle to expand between each tendinous intersection. [4]
The upper portion, attached principally to the cartilage of the fifth rib, usually has some fibers of insertion into the anterior extremity of the rib itself.
It is typically around 10 mm thick, [5] although, some athletes can have a rectus up to 20 mm thick. [6] Typical volume is around 300 cm3 in non-active individuals and 500 cm3 in athletes. [7]
The rectus abdominis has many sources of arterial blood supply. Classification of the vascular anatomy of muscles: First, the inferior epigastric artery and vein (or veins) run superiorly on the posterior surface of the rectus abdominis, enter the rectus fascia at the arcuate line, and serve the lower part of the muscle. Second, the superior epigastric artery, a terminal branch of the internal thoracic artery, supplies blood to the upper portion. Finally, numerous small segmental contributions come from the lower six intercostal arteries as well.
The muscles are innervated by thoraco-abdominal nerves, these are continuations of the T7-T11 intercostal nerves and pierce the anterior layer of the rectus sheath. Sensory supply is from the 7-12 thoracic nerves.
The sternalis muscle may be a variant form of the pectoralis major or the rectus abdominis. Some fibers are occasionally connected with the costoxiphoid ligaments, and the side of the xiphoid process.
The rectus abdominis is an important postural muscle. It is responsible for flexing the lumbar spine, as when doing a crunch. The rib cage is brought up to where the pelvis is when the pelvis is fixed, or the pelvis can be brought towards the rib cage (posterior pelvic tilt) when the rib cage is fixed, such as in a leg-hip raise. The two can also be brought together simultaneously when neither is fixed in space.
The rectus abdominis assists with breathing and plays an important role in respiration when forcefully exhaling, as seen after exercise as well as in conditions where exhalation is difficult such as emphysema. It also helps in keeping the internal organs intact and in creating intra-abdominal pressure, such as when exercising or lifting heavy weights, during forceful defecation or parturition (childbirth).
An abdominal muscle strain, also called a pulled abdominal muscle, is an injury to one of the muscles of the abdominal wall. A muscle strain occurs when the muscle is stretched too far. When this occurs the muscle fibers are torn. Most commonly, a strain causes microscopic tears within the muscle, but occasionally, in severe injuries, the muscle can rupture from its attachment.
A rectus sheath hematoma is an accumulation of blood in the sheath of the rectus abdominis muscle. It causes abdominal pain with or without a mass. The hematoma may be caused by either rupture of the epigastric artery or by a muscular tear. Causes of this include anticoagulation, coughing, pregnancy, abdominal surgery and trauma. With an ageing population and the widespread use of anticoagulant medications, there is evidence that this historically benign condition is becoming more common and more serious. [8]
On abdominal examination, people may have a positive Carnett's sign.
Most hematomas resolve without treatment, but they may take several months to resolve.
The rectus abdominis is similar in most vertebrates. The most obvious difference between animal and human abdominal musculature is that in animals, there are a different number of tendinous intersections.
The linea alba is a strong fibrous midline structure of the anterior abdominal wall situated between the two recti abdominis muscles. The umbilicus (navel) is a defect in the linea alba through which foetal umbilical vessels pass before birth. The linea alba is formed by the union of aponeuroses that collectively make up the rectus sheath. The linea alba attaches to the xiphoid process superiorly, and to the pubic symphysis inferiorly. It is narrow inferiorly where the two recti abdominis muscles are in contact with each other posterior to it, and broadens superior-ward from just inferior to the umbilicus.
Abdominal muscles cover the anterior and lateral abdominal region and meet at the anterior midline. These muscles of the anterolateral abdominal wall can be divided into four groups: the external obliques, the internal obliques, the transversus abdominis, and the rectus abdominis.
The inguinal ligament, also known as Poupart's ligament or groin ligament, is a band running from the pubic tubercle to the anterior superior iliac spine. It forms the base of the inguinal canal through which an indirect inguinal hernia may develop.
The transverse abdominal muscle (TVA), also known as the transverse abdominis, transversalis muscle and transversus abdominis muscle, is a muscle layer of the anterior and lateral abdominal wall, deep to the internal oblique muscle. It is thought by most fitness instructors to be a significant component of the core.
The pyramidalis muscle is a small triangular muscle, anterior to the rectus abdominis muscle, and contained in the rectus sheath.
The transversus thoracis muscle, also known as triangularis sterni, lies internal to the thoracic cage, anteriorly. It is usually a thin plane of muscular and tendinous fibers, however on athletic individuals it can be a thick 'slab of meat', situated upon the inner surface of the front wall of the chest. It is in the same layer as the subcostal muscles and the innermost intercostal muscles.
The abdominal internal oblique muscle, also internal oblique muscle or interior oblique, is an abdominal muscle in the abdominal wall that lies below the external oblique muscle and just above the transverse abdominal muscle.
The abdomen is the front part of the torso between the thorax (chest) and pelvis in humans and in other vertebrates. The area occupied by the abdomen is called the abdominal cavity. In arthropods, it is the posterior tagma of the body; it follows the thorax or cephalothorax.
In human anatomy, the inferior epigastric artery is an artery that arises from the external iliac artery. It is accompanied by the inferior epigastric vein; inferiorly, these two inferior epigastric vessels together travel within the lateral umbilical fold The inferior epigastric artery then traverses the arcuate line of rectus sheath to enter the rectus sheath, then anastomoses with the superior epigastric artery within the rectus sheath.
In human anatomy, the superior epigastric artery is a terminal branch of the internal thoracic artery that provides arterial supply to the abdominal wall, and upper rectus abdominis muscle. It enters the rectus sheath to descend upon the inner surface of the rectus abdominis muscle. It ends by anastomosing with the inferior epigastric artery.
In human anatomy, the superior epigastric veins are two or more venae comitantes which accompany either superior epigastric artery before emptying into the internal thoracic vein. They participate in the drainage of the superior surface of the diaphragm.
also known as superior tendon of abdominal cavity.
The arcuate line of rectus sheath is a line of demarcation corresponding to the free inferior margin of the posterior layer of the rectus sheath inferior to which only the anterior layer of the rectus sheath is present and the rectus abdominis muscle is therefore in direct contact with the transversalis fascia. The arcuate line is concave inferior-wards.
The rectus sheath is a tough fibrous compartment formed by the aponeuroses of the transverse abdominal muscle, and the internal and external oblique muscles. It contains the rectus abdominis and pyramidalis muscles, as well as vessels and nerves.
The anterior divisions of the seventh, eighth, ninth, tenth, and eleventh thoracic intercostal nerves are continued anteriorly from the intercostal spaces into the abdominal wall; hence they are named thoraco-abdominal nerves.
The rectus abdominis muscle is crossed by three fibrous bands called the tendinous intersections or tendinous inscriptions. One is usually situated at the level of the umbilicus, one at the extremity of the xiphoid process, and the third about midway between the two.
The aponeurosis of the abdominal external oblique muscle is a thin but strong membranous structure, the fibers of which are directed downward and medially.
Diastasis recti, or rectus abdominis diastasis, is an increased gap between the right and left rectus abdominis muscles. The increased distance between the muscles is created by the stretching of the linea alba, a connective collagen sheath created by the aponeurosis insertions of the transverse abdominis, internal oblique, and external oblique. This condition has no associated morbidity or mortality. Physical therapy is often required to repair this separation and surgery is an option for more severe cases. Standard exercise rarely results in complete healing of the separated muscles.
The following outline is provided as an overview of and topical guide to human anatomy:
A surgical incision is a cut made through the skin and soft tissue to facilitate an operation or procedure. Often, multiple incisions are possible for an operation. In general, a surgical incision is made as small and unobtrusive as possible to facilitate safe and timely operating conditions and recovery.