Muscularis externa

Template:Infobox Anatomy 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:

• in the pyloric stomach, it forms the pyloric sphincter
• in the anal canal, it forms the anal sphincter

Additional images

• 

  Wall of the ureter.

• 

  Layers of stomach wall.

• 

  Section of the human esophagus. Moderately magnified.

• 

  Section of duodenum of cat. X 60.

• 

  Vertical section of bladder wall.

External links

• Template:EMedicineDictionary
• Histology at nhmccd.edu
• Template:BiowebUW
• Template:BiowebUW
• Template:OklahomaHistology - "Duodenum"
• Template:UCDavisOrganology - "Mammal, whole system (LM, Low)"
• Template:UIUCHistologySubject
• Histology image: 11601ooa – Histology Learning System at Boston University - "Muscle Tissue: smooth muscle, muscularis externa"
• Histology image: 10802loa – Histology Learning System at Boston University - "Digestive System: Alimentary Canal - esophagus "