Mucosa

The mucosa, which lines the lumen of the GI tract, is the absorptive and major secretory layer. It consists of a simple columnar epithelium supported by the lamina propria, a thin layer of areolar connective tissue containing numerous lymph nodules, which are important in protecting against disease (fig. 18.3b). External to the lamina propria is a thin layer of smooth muscle called the muscularis mucosae. This is the muscle layer responsible for the numerous small folds in certain portions of the GI tract. These folds greatly increase the absorptive surface area. Specialized goblet cells in the mucosa secrete mucus throughout most of the GI tract.

Artery

Mesentery

Artery

Mesentery

Mucosa Submucosa

Muscularis externa

Muscularis Interna Externa

Plica circularis

Myenteric plexus

Submucosal plexus

Lymph nodule

Lacteal

Epithelium

Plica circularis

Mucosa Submucosa

Longitudinal muscle

Circular muscle

Muscularis externa

Myenteric plexus

Submucosal plexus

Lymph nodule

Lacteal

Epithelium

■ Figure 18.3 The layers of the digestive tract. (a) An illustration of the major tunics, or layers, of the small intestine. The insert shows how folds of mucosa form projections called villi in the small intestine. (b) An illustration of a cross section of the small intestine showing layers and glands.

The Digestive System Submucosa

The relatively thick submucosa is a highly vascular layer of connective tissue that serves the mucosa. Absorbed molecules that pass through the columnar epithelial cells of the mucosa enter into blood and lymphatic vessels of the submucosa. In addition to blood vessels, the submucosa contains glands and nerve plexuses. The submucosal plexus (Meissner's plexus) (fig. 18.3ft) provides an autonomic nerve supply to the muscu-laris mucosae.

Essentials of Human Physiology

Essentials of Human Physiology

This ebook provides an introductory explanation of the workings of the human body, with an effort to draw connections between the body systems and explain their interdependencies. A framework for the book is homeostasis and how the body maintains balance within each system. This is intended as a first introduction to physiology for a college-level course.

Get My Free Ebook


Responses

  • duane
    Is the mucosa of the small intestine thick or thin?
    7 years ago
  • michael
    Is the connective tissue of the mucosa called?
    6 years ago

Post a comment