Abdominal muscles

The anterior and lateral walls of the abdominal cavity are formed by three paired broad abdominal muscles, their tendon extensions, and the rectus abdominis muscles with their fasciae. The muscles and fasciae of the abdominal walls form the abdominal press, which protects the viscera from external influences, exerts pressure on them and holds them in a certain position, and also participates in the movements of the spine and ribs. The posterior wall of the abdominal cavity includes the lumbar spine, as well as the paired large lumbar and square lumbar muscles. The lower wall is formed by the iliac bones, muscles and fasciae of the pelvic floor - the pelvic diaphragm and the urogenital diaphragm.

The abdominal muscles and the fascia covering them form the muscular basis of the lateral, anterior and posterior walls of the abdominal cavity. According to the topography and the place of origin and attachment, the abdominal muscles can be divided into lateral, anterior and posterior.

Muscles of the lateral walls of the abdominal cavity

The lateral walls of the abdominal cavity are formed by three paired broad muscles: the external oblique abdominal muscle, the internal oblique abdominal muscle, and the transverse abdominal muscle. Arranged in layers, the bundles of these muscles run in different directions. In the external and internal oblique abdominal muscles, the muscle bundles cross each other at an angle of approximately 90°, and the bundles of the transverse abdominal muscle are oriented horizontally.

The external oblique muscle of the abdomen (m. obliquus extemus abdominis) is the most superficial and extensive of the abdominal muscles. It begins with large teeth on the outer surface of the eight lower ribs. The upper five teeth of the muscle enter between the teeth of the anterior serratus muscle, and the lower three - between the teeth of the latissimus dorsi muscle.

External oblique muscle of the abdomen

The internal oblique muscle of the abdomen (m. obhquus internus abdominis) is located inside the external oblique muscle of the abdomen, forming the second layer of muscles of the abdominal wall. The muscle begins at the intermediate line of the iliac crest, the lumbothacral fascia and the lateral half of the inguinal ligament.

Internal oblique muscle of the abdomen

The transverse abdominal muscle (m. transversus abdominis) forms the deepest, third layer in the lateral sections of the abdominal wall. The bundles of the transverse abdominal muscle are located horizontally, passing from behind to the front and medially.

Transverse abdominal muscle

Muscles of the anterior abdominal wall

The rectus abdominis muscle (m. rectus abdominis) is a flat, long, ribbon-shaped muscle located on the side of the midline. It is separated from the same muscle on the opposite side by the white line of the abdomen. The muscle begins with two tendinous parts - on the pubic bone (between the pubic symphysis and the pubic tubercle) and the pubic ligaments.

Rectus abdominis muscle

The pyramidal muscle (m. pyramidalis) has a triangular shape, is located in front of the lower part of the rectus abdominis muscle. The muscle begins at the pubic symphysis. The fibers of the muscle are directed from the bottom up and are woven into the white line of the abdomen. (Sometimes the muscle is absent.)

Pyramidal muscle

Muscles of the posterior abdominal wall

The quadratus lumborum muscle (m. quadratus lumborum) is located lateral to the transverse processes of the lumbar vertebrae. It originates on the iliac crest, the iliolumbar ligament, and the transverse processes of the lower lumbar vertebrae. It is attached to the lower edge of the 12th rib and the transverse processes of the upper lumbar vertebrae.

Quadratus lumborum muscle

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