The lamina muscularis mucosae (or muscularis mucosae) is a thin layer (lamina
) of muscle
of the gastrointestinal tract
, located outside the lamina propria
, and separating it from the submucosa
. It is present in a continuous fashion from the esophagus
to the upper rectum
(the exact nomenclature of the rectum's muscle layers is still being debated). A discontinuous muscularis mucosae–like muscle layer is present in the urinary tract
, from the renal pelvis
to the bladder
; as it is discontinuous, it should not be regarded as a true muscularis mucosae.
In the gastrointestinal tract
, the term ''mucosa'' or ''mucous membrane
'' refers to the combination of epithelium
, lamina propria, and (where it occurs) muscularis mucosae.
[H.G. Burkitt et al., ''Wheater's Functional Histology, 3rd ed.'']
The etymology suggests this, since the Latin names translate to "the mucosa's own special layer" (''lamina propria mucosae'') and "muscular layer of the mucosa" (''lamina muscularis mucosae'').
The muscularis mucosae is composed of several thin layers of smooth muscle fibers
oriented in different ways which keep the mucosal surface and underlying gland
s in a constant state of gentle agitation to expel contents of glandular crypts
and enhance contact between epithelium and the contents of the lumen
Image:Gray1033.png|Section of the human esophagus. Moderately magnified.
Image:Gray1053.png|Section of mucous membrane of human stomach, near the cardiac orifice.
Image:Gray1082.png|Section of mucous membrane of human rectum. X 60.
Image:Illu stomach layers.jpg|Layers of stomach wall
Image:Gut wall.svg|General structure of the gut wall showing the Muscularis mucosa.
Stacey E. Mills — Histology for Pathologists: 3rd (third) Edition, page 670.
* — "Lung"
* - "Mammal, whole system (LM, Low)"