Overview
It has a costal and a lumbar part. Its fleshy part covers the lateral abdominal wall and the caudoventral thorax; ventrally it continues as an aponeurosis that reaches the linea alba. The model shows the fleshy part.
Origin
- Costal part: lateral surfaces of the ribs from the fourth or fifth to the last, by digitations alternating with those of the serratus ventralis.
- Lumbar part: thoracolumbar fascia.
Insertion
Through its aponeurosis: linea alba, prepubic tendon and inguinal ligament.
Action
Compresses the abdomen (expiration, defecation, urination, parturition) and bends the trunk to the same side.
Innervation
Ventral branches of the caudal thoracic and cranial lumbar nerves.
Clinical relevance
Its aponeurosis contains the superficial inguinal ring, through which inguinal hernias can protrude.