Origin: Pubic crest and the pubic symphysis
Insertion: The costal cartilages of ribs 5-7 and the xiphoid process of the sternum
Actions: Flexion of the vertebral column
Innervation: Thoracoabdominal nerves (T7 to T11) and subcostal (T12)
Blood Supply: Branches from the musculophrenic artery, the lower two or three posterior intercostal arteries, the subcostal artery and branches from the superficial epigastric artery.
Primary Actions of the Abdominis Rectus
1. Flexion of the thoracic spine when acting bilaterally
Agonists: None
Antagonists:
- Iliocostalis cervicis
- Iliocostalis thoracics
- Iliocostalis lumborum
- Longissimus cervicis
- Longissimus thoracics
- Spinalis thoracics
- Semispinalis cervicis
Note: Internal oblique, external oblique, and psoas major assist with flexion of the thoracic spine.
2. Flexion of the lumber spine when acting bilaterally
Agonists: None
Antagonists:
- Iliocostalis lumborum
- Longissimus thoracics
- Spinalis thoracics
Note: Internal oblique, external oblique, and psoas major assist with flexion of the thoracic spine.
Secondary Actions of the Rectus Abdominis
1. Assists with forced expiration
Agonists:
- Serratus posterior inferior
- Transversus Abdominis
Antagonists:
- Serratus posterior superior
- Levatores costarum breve
- Levatores costarum longi
Note: The internal and external obliques also assist with forced expiration.