Muscularis externa

Muscular layer
Histological section of the ureter, showing the thick muscular layers surrounding the lumen.
Details
Latin	tunica muscularis
Dorlands /Elsevier	12832129
Anatomical terminology []

The muscular layer (muscular coat, muscular fibers, muscularis propria, muscularis externa) is a region of muscle in many organs in the vertebrate body, adjacent to the submucosa. It is responsible for gut movement such as peristalsis. The Latin, tunica muscularis, may also be used.

It usually has two layers of smooth muscle:

However, there are some exceptions to this pattern.

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

This article incorporates text in the public domain from the 20th edition of Gray's Anatomy (1918)