Muscularis externa

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Muscularis externa
longitudinal muscle
myenteric plexus
circular muscle
submucosal plexus
Transverse section of ureter.
Latin tunica muscularis
Dorlands/Elsevier t_22/12832129

Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]

The muscular coat (or muscular layer, or muscular fibers, or muscularis propria, or muscularis externa) is a region of muscle in many organs in the vertebrate body, adjacent to the mucous membrane. It is responsible for gut movement such as peristalsis.

It usually has two distinct layers of smooth muscle:

  • inner and "circular"
  • outer and "longitudinal"

However, there are some exceptions to this pattern.

  • In the stomach, there are three layers to the muscularis externa.
  • In the upper esophagus, part of the externa is skeletal muscle, rather than smooth muscle.

The inner layer of the muscularis externa forms a sphincter at two locations of the alimentary canal:

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This article was originally based on an entry from a public domain edition of Gray's Anatomy. As such, some of the information contained herein may be outdated. Please edit the article if this is the case, and feel free to remove this notice when it is no longer relevant.