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Pyramidalis muscle: want to learn more about it?

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Pyramidalis muscle

Pyramidalis muscle (Musculus pyramidalis)

Pyramidalis is a paired triangular muscle of the anterior abdominal wall found on each side of the linea alba. According to the narrowest anatomical classification, pyramidalis belongs to the anterior abdominal muscles, together with the rectus abdominis muscle. However, in a broader picture that takes the functional anatomy into account, these two muscles comprise the anterolateral abdominal wall along with the lateral abdominal muscles; external oblique, internal oblique and transversus abdominis muscles.

Pyramidalis muscle tenses the linea alba, which is an action that doesn't have a significant function when occurring on its own. However, acting together with the rest of the abdominal muscles, pyramidalis muscle contributes to a variety of abdominal wall functions, such as increasing the intra abdominal pressure when necessary (e.g. labor, forced expiration, defecation).

Key facts about the pyramidalis muscle
Origin Pubic crest, pubic symphysis
Insertion Linea alba
Action Tenses linea alba 
Innervation Subcostal nerve (T12) 
Blood supply Inferior epigastric artery

This article will discuss the anatomy and function of pyramidalis muscle.

Origin and insertion

Pyramidalis muscle originates from the pubic symphysis and pubic crest. The part of the muscle originating from the symphysis arises by ligamentous fibers, while the bony attachment arises by tendinous fibers. The muscle belly narrows down as it courses superiorly and inserts to the linea alba, halfway between the umbilicus and pubis.

Relations

Pyramidalis muscle lies within the rectus sheath, a multilayered fascial compartment composed of the aponeuroses of the external abdominal oblique, internal abdominal oblique and transversus abdominis muscles. Within the sheath, pyramidalis lies superficially to the inferior part of rectus abdominis muscle.

Innervation

Pyramidalis is innervated by the subcostal nerve, which is the anterior ramus of spinal nerve T12.

Blood supply

Blood supply to the pyramidalis muscle comes from branches of the inferior epigastric artery.

Function

Pyramidalis muscle tenses the linea alba. The muscle usually contracts together with the other abdominal muscles, contributing to contracting the abdominal wall and increasing the positive abdominal pressure. 

These actions play a dual role. The first is as an important defense mechanism, whereby contraction of the abdominal muscles physically protects the abdominal organs. The second is to support certain physiological processes such as forced respiration, singing, micturition and defecation.

Pyramidalis muscle: 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 1,299,304 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:

  • Cael, C. (2010). Functional anatomy: Musculoskeletal anatomy, kinesiology, and palpation for manual therapists. Philadelphia, PA: Wolters Kluwer Health/Lippincott, Williams & Wilkins.
  • Moore, K. L., Dalley, A. F., & Agur, A. M. R. (2014). Clinically Oriented Anatomy (7th ed.). Philadelphia, PA: Lippincott Williams & Wilkins.
  • Netter, F. (2019). Atlas of Human Anatomy (7th ed.). Philadelphia, PA: Saunders.
  • Palastanga, N., & Soames, R. (2012). Anatomy and human movement: structure and function (6th ed.). Edinburgh: Churchill Livingstone.
  • Standring, S. (2016). Gray's Anatomy (41tst ed.). Edinburgh: Elsevier Churchill Livingstone.

Illustrations:

  • Pyramidalis muscle (Musculus pyramidalis) - Yousun Koh
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