Rectus Sheath anatomy definition & function
Rectus Sheath anatomy definition & function . This is an aponeurotic sheath covering the rectus
abdominis. It has two walls, anterior and posterior.
It is complete, covering the muscles from end to end.
Its composition is variable as described below.
It is firmly adherent to the tendinous intersections of the rectus muscle.
1. It is incomplete, being deficient above the costal
margin and below the arcuate line.
2. Its composition is variable as described below.
3. It is free from the rectus muscle.
Fusion of all the aponeurosis in the midline. It is called as Linea alba. It is called linea semilunaris, it extends from tip of 9th costal cartilage to pubic tubercle.
Details about the formation of the walls are as follows
Above the costal margin
Anterior wall : External oblique aponeurosis.
Posterior wall : It is deficient, the rectus muscle rests directly on the 5th, 6th and 7th costal cartilages.
Between the costal margin and the arcuate line
Anterior wall: External oblique aponeurosis and anterior lamina of the aponeurosis of the internal oblique.
Posterior wall: Posterior lamina of the aponeurosis of the internal oblique and aponeurosis of the transversus muscle. Midway between the umbilicus and the pubic symphysis, the posterior wall of the rectus sheath ends in the arcuate line or linea semicircularis or fold of Douglas. The line is concave downwards.
Below the arcuate line
Anterior wall : Aponeuroses of all the three flat muscles of the abdomen. The aponeuroses of the transversus and the internal oblique are fused, but the external oblique aponeurosis remains separate.
Posterior wall: It is deficient. The rectus muscle rests on the fascia transversalis.
1 The rectus abdomlrls is the chief and largest content.
2 The pyramidalis (if present) lies in front of the lower part of the rectus abdominis.
1. The superior epigastric artery enters the sheath by
passing between the costal and xiphoid origins of
the diaphragm. It crosses the upper border of the
transversus abdominis behind the seventh costal
cartilage. It supplies the rectus abdominis muscle and anastomoses with the inferior epigastric artery.
2. The inferior epigastric artery enters the sheath by
passing in front of the arcuate line.
1. The superior epigastric aena comitantes accornpany its artery and join the vena comitantes of internal thoracic vein.
2. The inferior epigastric oena comitantes accornpany its artery and join the external iliac vein.
These are the terminal parts of the lower six thoracic nerves, including the lower five intercostal nerves and the subcostal nerves
1. It checks bowing of rectus muscle during its contraction and thus increases the efficiency of the muscle.
2. It maintains the strength of the anterior abdominal wall.
New concept to Rectus sheath
Rectus sheath is formed by decussating fibres from
three abdominal muscles of each side. Each forms a
bilaminar aponeurosis at their medial borders. Fibres from all three anterior leaves run obliquely upwards, while the posterior fibers run obliquely downwards at right angles to anterior leaves.
Anterior sheath of rectus
Both leaves of external oblique aponeurosis and anterior leaf of internal oblique aponeurosis.
Posterior leaf of aponeurosis of internal oblique and
both leaves of aponeurosis of transversus abdominis. Fibres of each layer decussate to the opposite side of the sheath. Fibres also decussate between anterior and posterior sheaths. The three lateral abdominal muscles may be said to
be digastric with a central tendon in the form of linea alba.
Linea alba is a tendinous raphe between xiphoid
process above to symphysis pubis and pubic crest
below. Above the umbilicus the linea alba is broader. Superficial fibres of linea alba are attached to symphysis pubis, while deep fibres are attached behind rectus
abdominis to posterior surface of pubic crest.
So this is all about Rectus Sheath anatomy definition & Function