MUSCLES OF THE ABDOMINAL WALL

MUSCLES OF THE ABDOMINAL WALL

There are six pairs of muscles that form the abdominal wall.from the surface inwards they are.

v  Rectus abdominis

v  External oblique

v  Internal oblique

v  Transversus abdominis

v  Quadratus lumborum

v  Psoas .

 The anterior abdominal wall is divided longitudinally by a very strong midline tendinous cord,the linea alba (meaning ‘white cord’) which extends from the xiphoid process of the sternum to the symphysis pubis.

The structure of the abdominal wall on each side of the linea alba is identical.

RECTUS ABDOMINIS.

This is the most superficial muscle.

It is broad and flat ,originating from the transverse part of the pubic bone then passing upwards to be inserted into the lower ribs and the xiphoid process of the sternum.

Medially the two muscles are attached to the linea alba.

EXTERNAL OBLIQUE

This muscle extends from the lower ribs downwards and forwards to be inserted into the iliac crest and by an aponeurosis,to the linea alba .

Internal oblique

This muscle lies deep to the external oblique.

Its fibres arise from the iliac crest and by a broad band of fascia from the spinous processes of the lumbar vertebrae.

The fibres pass upwards towards the midline to be inserted into the lower ribs and by an aponeurosis , into the linea alba. The fibres are at right angles to those of the external oblique.

TRANSVERSE ABDOMINIS

This is the deepest muscle of the abdominal wall.

The fibres arise from the iliac crest and the lumbar vertebrae and pass across the abdominal wall to be inserted into the linea alba by an aponeurosis.

The fibres are at right angles to those of the rectus abdominis.

Functions

The main function of the four pairs of muscles is to form the strong muscular anterior wall of the abdominal cavity.

When the muscles contract together they:

Ø  Compress the abdominal organs.

Ø  Flex the vertebral column in the lumbar region.

Ø  Contraction of the muscles on one side only bends the trunk towards that side.contraction of the oblique muscles on one side rotates the trunk.

INGUINAL CANAL

This canal is 2.5 to 4 cm long and passes obliquely through the abdominal wall.

It runs parallel to and immediately infront of the transversalis fascia and part of the inguinal ligament .

In the male it contains the spermatic cord and in the female, the round ligament.

It constitutes a weak point in the otherwise strong abdominal through which herniation may occur.