The rectus abdominis muscle, ( la, straight abdominal) also known as the "abdominal muscle" or simply the "abs", is a paired straight
muscle.
It is a paired muscle, separated by a midline band of
connective tissue called the
linea alba. It extends from the
pubic symphysis
The pubic symphysis is a secondary cartilaginous joint between the left and right superior rami of the pubis of the hip bones. It is in front of and below the urinary bladder. In males, the suspensory ligament of the penis attaches to the pubi ...
,
pubic crest
Medial to the pubic tubercle is the pubic crest, which extends from this process to the medial end of the pubic bone.
It gives attachment to the conjoint tendon, the rectus abdominis, the abdominal external oblique muscle, and the pyramidalis mu ...
and
pubic tubercle
The pubic tubercle is a prominent tubercle on the superior ramus of the pubis bone of the pelvis.
Structure
The pubic tubercle is a prominent forward-projecting tubercle on the upper border of the medial portion of the superior ramus of the ...
inferiorly, to the
xiphoid process
The xiphoid process , or xiphisternum or metasternum, is a small cartilaginous process (extension) of the inferior (lower) part of the sternum, which is usually ossified in the adult human. It may also be referred to as the ensiform process. Bo ...
and
costal cartilages
The costal cartilages are bars of hyaline cartilage that serve to prolong the ribs forward and contribute to the elasticity of the walls of the thorax. Costal cartilage is only found at the anterior ends of the ribs, providing medial extension.
...
of ribs V to VII superiorly. The proximal attachments are the pubic crest and the pubic symphysis. It attaches distally at the costal cartilages of ribs 5-7 and the xiphoid process of the sternum.
The rectus abdominis muscle is contained in the
rectus sheath
The rectus sheath, also called the rectus fascia,. is formed by the aponeuroses of the transverse abdominal and the internal and external oblique muscles. It contains the rectus abdominis and pyramidalis muscles.
Structure
The rectus sheat ...
, which consists of the
aponeuroses
An aponeurosis (; plural: ''aponeuroses'') is a type or a variant of the deep fascia, in the form of a sheet of pearly-white fibrous tissue that attaches sheet-like muscles needing a wide area of attachment. Their primary function is to join muscl ...
of the lateral abdominal muscles. The outer, most lateral line, defining the rectus is the
linea semilunaris
The linea semilunaris (also semilunar line or Spigelian line) is a curved tendinous intersection found on either side of the rectus abdominis muscle.
Structure
The linea semilunaris corresponds with the lateral border of the rectus abdominis m ...
. Bands of
connective tissue traverse the rectus abdominis, separating it into distinct muscle bellies. In the abdomens of people with low body fat, these muscle bellies can be viewed externally. They can appear in sets of as few as two to as many as twelve, although, six is the most common.
Structure
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.
[Abdomen, in Moore, K.L., Dalley, A.F., Agur, A.M.R. (eds). 2014. Clinically Oriented Anatomy: Seventh Edition. Lippincott Williams & Wilkins. Philadelphia. PA. pg:191.]
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.
Size
It is typically around 10 mm thick., although, some athletes can have a rectus up to 20 mm thick.
Typical volume is around 300 cm³ in non-active individuals and 500 cm³ in athletes.
Blood supply
The rectus abdominis has many sources of arterial blood supply. Classification of the vascular anatomy of muscles: First, the
inferior epigastric artery
In human anatomy, inferior epigastric artery refers to the artery that arises from the external iliac artery. It anastomoses with the superior epigastric artery. Along its course, it is accompanied by a similarly named vein, the inferior epig ...
and vein (or veins) run superiorly on the posterior surface of the rectus abdominis, enter the
rectus fascia
The rectus sheath, also called the rectus fascia,. is formed by the aponeuroses of the transverse abdominal and the internal and external oblique muscles. It contains the rectus abdominis and pyramidalis muscles.
Structure
The rectus sheath ...
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.
Nerve supply
The muscles are innervated by
thoraco-abdominal 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 (or thoracicoabdomin ...
, these are continuations of the T7-T11
intercostal nerves and pierce the anterior layer of the
rectus sheath
The rectus sheath, also called the rectus fascia,. is formed by the aponeuroses of the transverse abdominal and the internal and external oblique muscles. It contains the rectus abdominis and pyramidalis muscles.
Structure
The rectus sheat ...
. Sensory supply is from the 7-12
thoracic nerves
A spinal nerve is a mixed nerve, which carries motor, sensory, and autonomic signals between the spinal cord and the body. In the human body there are 31 pairs of spinal nerves, one on each side of the vertebral column. These are grouped into t ...
.
Variation
The
sternalis muscle
The sternalis muscle is an anatomical variation that lies in front of the sternal end of the pectoralis major parallel to the margin of the sternum. The sternalis muscle may be a variation of the pectoralis major or of the rectus abdominis.
Struc ...
may be a
variant form of the
pectoralis major or the rectus abdominis. Some fibers are occasionally connected with the
costoxiphoid ligaments
The costoxiphoid ligaments (chondroxiphoid ligaments) are inconstant strand-like fibrous bands that connect the anterior and posterior surfaces of the seventh costal cartilage, and sometimes those of the sixth, to the front and back of the xiphoid ...
, and the side of the
xiphoid process
The xiphoid process , or xiphisternum or metasternum, is a small cartilaginous process (extension) of the inferior (lower) part of the sternum, which is usually ossified in the adult human. It may also be referred to as the ensiform process. Bo ...
.
Function
The rectus
abdominis is an important
postural muscle. It is responsible for flexing the
lumbar spine
The lumbar vertebrae are, in human anatomy, the five vertebrae between the rib cage and the pelvis. They are the largest segments of the vertebral column and are characterized by the absence of the foramen transversarium within the transverse p ...
, 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
Respiration may refer to:
Biology
* Cellular respiration, the process in which nutrients are converted into useful energy in a cell
** Anaerobic respiration, cellular respiration without oxygen
** Maintenance respiration, the amount of cellul ...
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).
Clinical significance
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
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. Cau ...
is an accumulation of blood in the sheath of the rectus abdominis muscle. It causes
abdominal pain
Abdominal pain, also known as a stomach ache, is a symptom associated with both non-serious and serious medical issues.
Common causes of pain in the abdomen include gastroenteritis and irritable bowel syndrome. About 15% of people have a m ...
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
Anticoagulants, commonly known as blood thinners, are chemical substances that prevent or reduce coagulation of blood, prolonging the clotting time. Some of them occur naturally in blood-eating animals such as leeches and mosquitoes, where the ...
,
coughing,
pregnancy
Pregnancy is the time during which one or more offspring develops (gestation, gestates) inside a woman, woman's uterus (womb). A multiple birth, multiple pregnancy involves more than one offspring, such as with twins.
Pregnancy usually occur ...
,
abdominal surgery
The term abdominal surgery broadly covers surgical procedures that involve opening the abdomen (laparotomy). Surgery of each abdominal organ is dealt with separately in connection with the description of that organ (see stomach, kidney, liver, etc ...
and
trauma
Trauma most often refers to:
* Major trauma, in physical medicine, severe physical injury caused by an external source
* Psychological trauma, a type of damage to the psyche that occurs as a result of a severely distressing event
*Traumatic i ...
. 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.
On
abdominal examination
An abdominal examination is a portion of the physical examination which a physician or nurse uses to clinically observe the abdomen of a patient for signs of disease. The physical examination typically occurs after a thorough medical history i ...
, people may have a
positive
Positive is a property of positivity and may refer to:
Mathematics and science
* Positive formula, a logical formula not containing negation
* Positive number, a number that is greater than 0
* Plus sign, the sign "+" used to indicate a posi ...
Carnett's sign
In medicine, Carnett's sign is a finding on clinical examination in which (acute abdomen, acute) abdominal pain remains unchanged or increases when the muscles of the abdominal wall are tensed. For this part of the abdominal examination, the patien ...
.
Most hematomas resolve without treatment, but they may take several months to resolve.
Other animals
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.
Additional images
File:Gray399.png, Diagram of sheath of rectus
File:Illu trunk muscles.jpg, Muscles of the trunk
File:2018-10-07 MAG Training at 2018 Summer Youth Olympics (Martin Rulsch) 21.jpg, Gymnast Félix Dolci
Félix Dolci (born 5 May 2002) is a Canadian male artistic gymnast. He is the 2019 Junior World Champion on rings. He has been a member of the Canadian national team since 2017.
Early life
Dolci was born in Saint-Eustache, Québec in 2002 ...
, who has a visible rectus abdominis
File:2018-10-05 WAG Training at 2018 Summer Youth Olympics (Martin Rulsch) 410.jpg, Gymnast Nazlı Savranbaşı, who has a visible rectus abdominis
See also
*
Divarication of rectus abdominis muscles
References
External links
* – "Muscles of the anterior
chest wall with the pectoralis major muscles removed."
* – "Thoracic Wall: The Anterior Thoracic Wall"
* – "Incision and reflection of the
external abdominal oblique muscle."
* – "Incision and reflection of the
internal abdominal oblique
The abdominal internal oblique muscle, also internal oblique muscle or interior oblique, is an Abdomen#Muscles, abdominal muscle in the abdominal wall that lies below the external oblique muscle and just above the transverse abdominal muscle.
Str ...
muscle."
* – "Anterior Abdominal Wall: The Rectus Abdominis Muscle"
*
*
{{DEFAULTSORT:Rectus Abdominis Muscle
Muscles of the torso
Spine flexors