This is the Rectus Abdominis
AKA  “Abdominal Muscles” and “Abs”

Origins:

  • the superior edge of the pubis bone
  • the pubic symphysis in the pelvis.

Insertions:

  • The inferior edges of the costal cartilages of the fifth through seventh ribs
  • The xiphoid process of the sternum.

Actions:

  • performs the important task of flexing the torso and spine in the abdominal region.
    • It does this by pulling the rib cage closer to the pelvis.
  • The rectus abdominis can also tense to contract the abdomen without moving the torso, as in sucking in one’s gut.
  • Assists in breathing.
    • when forcefully exhaling, as seen after exercise as well as in conditions where exhalation is difficult such as emphysema.
  • It also helps in keeping the internal organs intact and in creating intra-abdominal pressure, such as when exercising or lifting heavy weights, during forceful defecation (bowel movements) or childbirth.

What Gives the “Abs” Their Shape?

  • Bands of connective tissue called the Tendinous Intersections traverse the Rectus Abdominis, which separates this parallel muscle into distinct muscle bellies.
  • Between the rectus abdominis muscles is a thick mass of white fibrous connective tissue called the Linea Alba that unites the abdominal muscles of the left and right sides.
  • The outer, most lateral line, defining the “abs” is the Linea Semilunaris (attachment sites for the external oblique and the transverse abdominis).

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