L5.5.4: Abdominal Muscles

• ABDOMINAL MUSCLES

  [a] Rectus Abdominis

  [b] External Oblique

  [c] Internal Oblique

  [d] Transversus Abdominis

  
• Rectus Abdominis

  ○ Most superficial muscles of the abdomen

  ○ Run from the pubis to the rib cage enclosed in an aponeurosis

  ○ Functions:

  ■ Flex the vertebral column

  ■ Compresses the abdominal contents during defecation and childbirth (helps the mother push)

  ■ Involved in forced breathing
• External Oblique

  ○ Make up the lateral walls of the abdomen

  ○ Their fibers run downward and medially from the last 8 ribs and insert into the ilium

  ○ Functions:

  ■ Also flex the vertebral column

  ■ Rotate the trunk and bend it literally
• Internal Oblique

  ○ Deep to the external obliques

  ○ Their fibers run at right angles to those of the external obliques

  ○ Arise from the iliac crest and insert into the last 3 ribs

  ○ Function the same as external oblique
• Transversus Abdominis (seen on the posterior side of the abdomen)

  ○ Deepest muscle of the abdominal wall

  ○ Its fibers run horizontally across the abdomen

  ○ Arises from the lower ribs and iliac crest and inserts into the pubis

  ○ Compresses the abdominal contents like a wide belt