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Anterior Abdominal Muscles

The anterior abdominal muscles are part of the abdominal wall musculature. They tense the anterior abdominal wall together with the lateral abdominal muscles. There are two muscles in the anterior abdominal wall, as follows:

  • rectus abdominis
  • pyramidalis

Out of the two muscles, the rectus abdominis is the only active one in humans, helping to tense the abdominal wall and moving the trunk, while the pyramidalis is rudimentary. This article will describe the two muscles of the anterior abdominal wall, together with their innervation and functions.

Key Facts about the Rectus Abdominis Muscle
Origin

Pubis

Insertion 5th to 7th costal cartilage and the xiphoid process
Innervation Intercostal nerves
Function Flexion the trunk, vertebral column stabilization, abdominal wall tensioning, increase intra-abdominal pressure, breathing
Clinical Hyperlordosis, hernias

Anatomy

The anterior abdominal muscles consist of:

  • Rectus abdominis muscle: originates from the pubis (between the pubic tubercle and symphysis) and inserts at the 5th to 7th costal cartilage and the xiphoid process of the sternum. Thereby it passes through the rectus sheath, a tendinous muscle envelope built by the aponeurosis of the lateral abdominal muscles. The rectus abdominis muscle has 3-4 horizontal tendinous intersections which are adhered to the anterior layer of the rectus sheath giving it its multi-bellied appearance (“washboard stomach”). These are traces of the segmental arrangement during embryogenesis (metamerism). The innervation is carried by the lower intercostal nerves.
  • Pyramidalis muscle: runs diagonally from the pubis (ventral to the insertion of the rectus abdominis muscle) within the rectus sheath to the linea alba. It is innervated by the subcostal nerve (12th intercostal nerve).

Function

The main tasks of the rectus abdominis muscle and the lateral abdominal muscles are the: 

  • movement of the trunk
  • stabilization of the vertebral column
  • tensioning of the abdominal wall
Recommended video: Rectus abdominis muscle
Origin, insertion, innervation and function of the rectus abdominis muscle.

They are responsible for the abdominal press, increasing the intra-abdominal pressure (e.g. during defecation or vomiting). Furthermore, they support the exhalation by pulling down the thorax through their contraction (expiratory breathing muscles). In particular, the rectus abdominis muscle does a ventral flexion (flexion of the trunk or erection of the pelvis) and thus is an important antagonist of the intrinsic back muscles.

Recommended video: Pyramidalis muscle
Origin, insertion, innervation and function of the pyramidalis muscle

The pyramidalis is a rudimentary muscle and relates to the pouch muscle of monotremes (e.g. hedgehog, duckbill) and marsupials (e.g. koala, kangaroo). Its original function, tensioning of the linea alba, does not play a role in higher mammals anymore.

Clinical Aspects

Abdominal muscles stabilize the vertebral column together with the back musculature. If they are poorly developed they cannot keep up to the antagonistic force of the back muscles. In the long term, this leads to hyperlordosis of the lumbar vertebral column and anterior pelvic tilt.

The tension of the abdominal muscles counters the weight of the internal abdominal organs. In case of overload (e.g. obesity, pregnancy) the increased intra-abdominal pressure can cause a hernial opening of the abdominal wall through which viscera (guts) may protrude. Predisposed weaknesses are often areas with few muscles such as the linea alba (epigastric hernia), the navel (umbilical hernia) and the inguinal ligament (inguinal hernia). On the contrary there is no hernial opening in diastasis recti, a condition where the rectus sheaths spread apart from the linea alba.

Anterior Abdominal Muscles - want to learn more about it?

Our engaging videos, interactive quizzes, in-depth articles and HD atlas are here to get you top results faster.

Sign up for your free Kenhub account today and join over 852,397 successful anatomy students.

“I would honestly say that Kenhub cut my study time in half.” – Read more. Kim Bengochea Kim Bengochea, Regis University, Denver

Show references

References:

  • M. Schünke/E. Schulte/U. Schumacher: Prometheus – LernAtlas der Anatomie – Allgemeine Anatomie und Bewegungssystem, 2.Auflage, Thieme Verlag (2007), S.152-155
  • M. Schünke: Funktionelle Anatomie – Topographie und Funktion des Bewegungssystems, 1.Auflage, Thieme Verlag (2000), S.192-206
  • H. Lippert: Lehrbuch Anatomie, 8.Auflage, Urban & Fischer Verlag/Elsevier (2011), S.179-182
  • C. Gegenbauer: Lehrbuch der Anatomie des Menschen, Band 3, Salzwasser Verlag (2012, Nachdruck des Originals von 1899), S.402-403

Author & Layout:

  • Achudhan Karunaharamoorthy
  • Christopher A. Becker

Illustrators:

  • Rectus abdominis muscle - ventral view - Yousun Koh
  • Pyramidalis muscle - ventral view - Yousun Koh
© Unless stated otherwise, all content, including illustrations are exclusive property of Kenhub GmbH, and are protected by German and international copyright laws. All rights reserved.

Related Atlas Images

Muscles of the ventral trunk

Main muscles of the trunk

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