4. Serosa / adventitia
Inner circular muscle
Outer longitudinal muscle
band (teniae coli)
General structure of the wall of the digestive tract.
can be divided into several basic tunics (layers) based on histologic organization. (1)
lamina propria, and muscularis mucosae. The epithelium is composed of simple columnar cells in most of the digestive tract, except
for stratiF ed squamous cells in the esophagus and anal canal. The lamina propria is a layer of loose connective tissue beneath the
epithelium. The muscularis mucosae is a thin layer of smooth muscle; it marks the boundary between the mucosa and the submucosa.
: dense irregular connective tissue with blood vessels, lymphatic vessels, and
submucosal plexuses (Meissner plexuses)
Mucous glands may be present in this layer. (3)
: two or three layers of smooth muscle. It may also include skeletal
muscle as in the esophagus. There are blood vessels and
myenteric (Auerbach) plexuses
that lie between the muscle layers. (4)
: The outermost layer is called
if it is composed of loose connective tissue with blood vessels and nerves passing
through and is covered by
. It is called
if covered by a layer of connective tissue without mesothelium lining.
The serosa covers organs within the abdominal or pelvic cavities (intraperitoneal), whereas the adventitia covers organs and serves
as a capsule and attachment between the organs or between an organ and the body wall (retroperitoneal).
Mucous glands and lymphatic nodules may be
3. Muscularis Externa
Inner circular muscle layer
Outer longitudinal muscle layer
Oblique muscle layer (stomach)
Serosa: outermost layer composed of connective
covered by mesothelium
Adventitia: outermost layer composed of connective
without mesothelium covering
Tunics (Layers) of the Digestive Tract