- Rectus abdominis
- The rectus abdominis is a paired group of longitudinal muscles found in the midline.
- They are separated by the linea alba and held in the rectus sheath as described above.
- Their origin is on the symphysis pubis and the pubic crest and the rectus abdominis runs to the xiphoid process and lower costal cartilage.
- There are also tendinous insertions between the muscle and the anterior rectus sheath found mainly above the arcuate line. These function to anchor the muscle to the anterior sheath.
- Function of the rectus abdominis is in locomotion and increasing intraabdominal pressure.
- The inferior epigastric artery supplies the lower portion of the muscle and enters the rectus sheath posteriorly at the arcuate line. This vessel anastomoses with the superior epigastric artery, which supplies the upper portion of the muscle.
- Nerve supply to the rectus abdominis is derived from the intercostal and lumbar nerves, which enter the rectus sheath laterally.
External oblique muscle
- The most superficial of the lateral abdominal muscles.
- It runs from its origin on the lower eight ribs to its insertion on the pubic crest, pubic tubercle, linea alba, and xiphoid process.
- This muscle functions mainly to assist respirations and increasing abdominal pressure. It has a minor role in locomotion.
- Its aponeurosis forms part of the anterior rectus sheath.
Internal oblique muscle
- This muscle is found deep to the external oblique.
- Its origin is on the lumbar fascia, iliac crest, and inguinal ligament.
- It inserts on the symphysis pubis, linea alba, lower ribs, and xiphoid process.
- The rectus sheath is partially formed by its aponeurosis, as mentioned previously.
- Its fibers run perpendicular to the external oblique’s fibers.
- It, too, functions mainly in respiration, increasing abdominal pressure, and locomotion.
- This muscle lies deep to the internal oblique.
- It arises from the lower costal cartilages, lumbar fascia, iliac crest, and inguinal ligament.
- Its insertion is found on the symphysis pubis, linea alba, and xiphoid process.
- Functions include respiration, increasing abdominal pressure, and locomotion.
- Its aponeurosis is part of the anterior and posterior rectus sheath, as mentioned.
A composite of the muscles of the anterior abdominal wall of the adult female. The superficial muscles are shown in the left side of the drawing, and the rectus abdominis and external and internal oblique muscles have been removed in the right side of the drawing.