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Inner oblique abdominal muscle
Last reviewed: 23.04.2024
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The internal oblique abdominal muscle (m. Obhquus internus abdominis) is located inside of the outer oblique abdominal muscle, forming the second layer of abdominal wall muscles. The muscle begins on the intermediate line of the iliac crest, the lumbosacral fascia and the lateral half of the inguinal ligament.
Bunches of the posterodrainer part of the muscle go from bottom to top and attach to the cartilages of the lower ribs, having the same direction with the beams of the internal intercostal muscles. The lower fascicles of the muscle fan outwardly and upwardly and move into a wide aponeurosis along a line drawn down from the cartilage X of the rib to the pubic bone. At the level of this line, the aponeurosis of the inner oblique muscle of the abdomen is split into two plates, covering the rectus abdominis at the front and back. The lower part of the aponeurosis is a continuation of that part of the muscle that begins on the lateral half of the inguinal ligament.
The bundles of the lower part of the muscle, together with the beams separating from the transverse abdominal muscle, are part of the spermatic cord and form the muscle that lifts the egg (m. Cremaster).
Function: with bilateral reduction, the inner oblique abdominal muscles flex the spine. With a one-sided contraction along with the external oblique muscle of the abdomen of the opposite side, the inner oblique abdominal muscle turns the trunk towards it, lowers the rib. With a strengthened chest lifts the pelvis.
Innervation: intercostal nerves (ThVI-ThXII), ilio-hypogastric (ThXII-LI) and ilio-inguinal (LI) nerves.
Blood supply: posterior intercostal arteries, upper and lower epigastric arteries, muscular-diaphragmatic artery.
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