Muscular layer

Updated on Oct 04, 2024

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Latin tunica muscularis		Dorlands/Elsevier 12832129

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.

Structure

It usually has two 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.

In the vas deferens of the spermatic cord, there are three layers: inner longitudinal, middle circular, and outer longitudinal.

In the ureter the smooth muscle orientation is opposite that of the GI tract. There is an inner longitudinal and an outer circular layer.

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

in the pylorus of the stomach, it forms the pyloric sphincter

in the anal canal, it forms the internal anal sphincter

References

Muscular layer Wikipedia

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