Muscles of the Abdominal Wall

Muscles of the Abdominal Wall

• External oblique muscle: originates from inferior eight ribs, inserts into linea alba and iliac crest, and acts to compress abdomen and flex vertebral column; also laterally flexes vertebral column (especially lumbar vertebrae) when acting singly; innervated by lower seven intercostal nerves and iliohypogastric nerves.
• Internal oblique muscle: originates from iliac crest and inguinal ligament, inserts into linea alba and cartilage of 8-10 ribs, and acts to compress abdomen; innervated by last three intercostal nerves, iliohypogastric, and ilioinguinal nerves.
• Transverse abdominis muscle: originates from iliac crest, inguinal ligament, and lower ribs, inserts into linea alba and pubic bone, and acts to compress abdomen; innervated by last five intercostal nerves, iliohypogastric, and ilioinguinal nerves.
• Rectus abdominis muscle: originates from pubic crest and symphysis pubis, inserts into xiphoid process and cartilage of fifth to seventh ribs, and acts to compress abdomen.
• Quadratus lumborum muscle: originates from iliolumbar ligament and iliac crest, inserts into inferior border of last rib and transverse process of vertebrae (L1-L4), and acts to compress abdomen, aid in defecation, urination, and forced exhalation, and flex vertebral column (especially lumbar vertebrae); innervated by last six intercostal nerves and lumbar nerves.

Muscles of the Back

• The muscles of the back play an important role in maintaining upright body posture.
• The muscles of the back can be grouped into several groups on either side of the vertebral column, extending from the occiput to the sacrum.
• The upper muscles extend the neck, while the lower muscles, including the erector spinae, straighten the spine.
• In the lumbar region, the muscles form a large aponeurosis called the lumbar fascia.