The muscular layer (muscular coat, muscular fibers, muscularis propria, muscularis externa) is a region of

muscle Muscle is a soft tissue, one of the four basic types of animal tissue. There are three types of muscle tissue in vertebrates: skeletal muscle, cardiac muscle, and smooth muscle. Muscle tissue gives skeletal muscles the ability to muscle contra ...

in many organs in the vertebrate body, adjacent to the submucosa. It is responsible for gut movement such as

peristalsis Peristalsis ( , ) is a type of intestinal motility, characterized by symmetry in biology#Radial symmetry, radially symmetrical contraction and relaxation of muscles that propagate in a wave down a tube, in an wikt:anterograde, anterograde dir ...

. 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 The stomach is a muscular, hollow organ in the upper gastrointestinal tract of Human, humans and many other animals, including several invertebrates. The Ancient Greek name for the stomach is ''gaster'' which is used as ''gastric'' in medical t ...

, there are three layers to the muscular layer. Stomach contains an additional oblique muscle layer just interior to circular muscle layer. * In the upper

esophagus The esophagus (American English), oesophagus (British English), or œsophagus (Œ, archaic spelling) (American and British English spelling differences#ae and oe, see spelling difference) all ; : ((o)e)(œ)sophagi or ((o)e)(œ)sophaguses), c ...

, part of the externa is ''

skeletal muscle Skeletal muscle (commonly referred to as muscle) is one of the three types of vertebrate muscle tissue, the others being cardiac muscle and smooth muscle. They are part of the somatic nervous system, voluntary muscular system and typically are a ...

'', rather than smooth muscle. * In the

vas deferens The vas deferens (: vasa deferentia), ductus deferens (: ductūs deferentes), or sperm duct is part of the male reproductive system of many vertebrates. In mammals, spermatozoa are produced in the seminiferous tubules and flow into the epididyma ...

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

gastrointestinal tract The gastrointestinal tract (GI tract, digestive tract, alimentary canal) is the tract or passageway of the Digestion, digestive system that leads from the mouth to the anus. The tract is the largest of the body's systems, after the cardiovascula ...

: * in the pylorus of the

, it forms the

pyloric sphincter The pylorus ( or ) connects the stomach to the duodenum. The pylorus is considered as having two parts, the ''pyloric antrum'' (opening to the body of the stomach) and the ''pyloric canal'' (opening to the duodenum). The ''pyloric canal'' ends a ...

. * in the

anal canal The anal canal is the part that connects the rectum to the anus, located below the level of the pelvic diaphragm. It is located within the anal triangle of the perineum, between the right and left ischioanal fossa. As the final functional s ...

, it forms the internal anal sphincter. In the colon, the fibres of the external longitudinal smooth muscle layer are collected into three longitudinal bands, the teniae coli. The thickest muscularis layer is found in the

(triple layered) and thus maximum peristalsis occurs in the stomach. Thinnest muscularis layer in the alimentary canal is found in the

rectum The rectum (: rectums or recta) is the final straight portion of the large intestine in humans and some other mammals, and the gut in others. Before expulsion through the anus or cloaca, the rectum stores the feces temporarily. The adult ...

, where minimum peristalsis occurs.

Function

The muscularis layer is responsible for the peristaltic movements and segmental contractions in and the alimentary canal. The Auerbach's nerve plexus (myenteric nerve plexus) is found between longitudinal and circular muscle layers, it starts muscle contractions to initiate

References

External links

* * * * — "Muscle Tissue: smooth muscle, muscularis externa" {{Authority control Membrane biology