Page 547 - Atlas of Histology with Functional Correlations

CHAPTER 14 Digestive System Part II:

Esophagus and Stomach

GENERAL PLAN OF DIGESTIVE SYSTEM

—AN OVERVIEW

The digestive (gastrointestinal) tract is a long hollow tube extending from the

esophagus to the rectum. It includes the esophagus, stomach, small intestine
(duodenum, jejunum, and ileum), large intestine (colon), and rectum. The wall of
the digestive tube shows four distinct layers that represent the basic histologic
organization of the entire tract. These layers are the mucosa, submucosa,
muscularis externa, and serosa (or adventitia). Because the digestive tract

performs different functions during the digestive processes, the morphology of
these layers exhibits variations. These are primarily evident in the epithelium and
indicate the specific functions for each section of the tract.

Mucosa

The mucosa is the innermost layer of the digestive tube that consists of a lining
epithelium and glands that extend into the underlying layer of loose connective

tissue called the lamina propria. A thin inner circular and an outer longitudinal
layer of smooth muscle, called the muscularis mucosae, form the outer
boundary of the mucosa.

Submucosa

The submucosa is located inferior to the mucosa. It consists of dense irregular
connective tissue with numerous blood and lymph vessels and a submucosal
(Meissner) nerve plexus that contains postganglionic parasympathetic neurons.
The neurons and axons of the submucosal nerve plexus control the motility of

the mucosa and secretory activities of mucosal glands. In the initial portion of

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