Abdominal Muscle Anatomy
Original Editor - Anne Millar
- 1 Introduction
- 2 External Abdominal Oblique
- 3 Internal Abdominal Oblique
- 4 Transversus Abdominis
- 5 Rectus Abdominis
- 6 References
The abdominal muscles form the anterior and lateral abdominal wall and consist of the external abdominal obliques, the internal abdominal obliques, the rectus abdominis and the transversus abdominis . Acting together these muscles form a firm wall that protects the viscera and they help to maintain erect posture. In addition the contraction of these muscles helps in expiration and to increase the intra-abdominal pressure such as in sneezing, coughing, micturating, defecating, lifting and childbirth.
External Abdominal Oblique
The external abdominal obliques are supplied by the lower six thoracic nerves and the iliohypogastric and ilioinguinal nerves.
Both sides acting together, the external abdominal obliques flex the vertebral column by drawing the pubis towards the xiphoid process. Acting unilaterally it results in ipsilateral side flexion and contralateral rotation of the trunk.
Internal Abdominal Oblique
The internal abdominal obliques are innervated by the lower six thoracic nerves and the iliohypogastric and ilioinguinal nerves.
Acting unilaterally, contraction of the internal oblique results in ipsilateral side flexion and rotation of the trunk. It acts with the external oblique muscle of the opposite side to achieve this torsional movement of the trunk. It also acts to compress the abdominal viscera, pushing them up into the diaphragm, resulting in a forced expiration.
The transversus abdominus muscle is innervated by the lower six thoracic nerves and the iliohypogastric and ilioinguinal nerves.
Contraction of the transversus abdominis has a corset like effect , narrowing and flattening the abdomen. It's primary function is to stabilise the lumbar spine and pelvis before movement of the lower and /or upper limbs occur.
The rectus abdominis muscle is innervated by the lower six thoracic nerves.
The rectus abdominis is an important postural muscle. With a fixed pelvis, contraction results in flexion of the lumbar spine . When the ribcage is fixed contraction results in a posterior pelvic tilt. It also plays an important role in forced expiration and in increasing intra-abdominal pressure.
- Drake RL, Vogyl AW, Mitchell AW. Gray's anatomy for students. 3rd edition. Philadelphia: Churchill Livingstion Elsevier; 2015. 282p.
- Gray H. Grays Anatomy. 37th ed. Edinburgh: Churchill Livingstone, 1989.
- Mantle J, Haslam J, Barton S. Physiotherapy in Obstetrics and Gynaecology. 2nd Ed. Edinburgh: Butterworth Heinemann, 2004
- Drake RL, Vogyl AW, Mitchell AW. Gray's anatomy for students. 3rd edition. Philadelphia: Churchill Livingstion Elsevier; 2015. 286p
- Wikipedia. Internal Abdominal Obliques. http://en.wikipedia.org/wiki/Abdominal_internal_muscle
- Wikipedia. Transversus Abdominis. http://en.wikipedia.org/wiki/Transversis_abdominis_muscle
- Lee D. The Pelvic Girdle. 2nd Ed. Edinburgh: Churchill Livingstone, 1999.
- Wikipedia. Rectus Abdominis. http://en.wikipedia/org.wiki/Rectus_abdominis_muscle
- Anatomy Zone. Muscles of the Anterior Abdominal Wall-3D Anatomy Tutorial. Available from: http://www.youtube.com/watch?v=mvOajxO8mXO [last accessed 11/07/15]