Muscularis externa

Muscularis externa

Muscular layer

Meissner's plexus
Circular muscle
Auerbach's plexus
longitudinal muscle
Serosa or Adventitia
Transverse section of ureter.
Latin tunica muscularis

The muscular coat (muscular layer, muscular fibers, muscularis propria, muscularis externa) is a region of muscle in many organs in the vertebrate body, adjacent to the submucosa 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 and colon, 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:

Additional images

External links

  • eMedicine Dictionary
  • Histology at
  • Muscularis externa of the colon
  • Smooth muscle layers of the gut
  • 52_05 - "Duodenum"
  • Digestive/mammal/system1/system7 - "Mammal, whole system (LM, Low)"
  • 23
  • 11601ooa - "Muscle Tissue: smooth muscle, muscularis externa"
  • 10802loa - "Digestive System: Alimentary Canal - esophagus "

This article incorporates text from a public domain edition of Gray's Anatomy.