Gastrointestinal wall

From the inner cavity of the gut (the lumen) outwards, these are the mucosa, the submucosa, the muscular layer and the serosa or adventitia.

When viewed under the microscope, the gastrointestinal wall has a consistent general form, but with certain parts differing along its course.

It surrounds the cavity (lumen) of the tract and comes into direct contact with digested food (chyme).

Goblet cells secrete mucus, which lubricates the passage of food along and protects the intestinal wall from digestive enzymes.

The villi contain a lacteal, a vessel connected to the lymph system that aids in the removal of lipids and tissue fluids.

In the large intestines, villi are absent and a flat surface with thousands of glands is observed.

Underlying the epithelium is the lamina propria, which contains myofibroblasts, blood vessels, nerves, and several different immune cells, and the muscularis mucosa which is a layer of smooth muscle that aids in the action of continued peristalsis and catastalsis along the gut.

The gut has intrinsic peristaltic activity (basal electrical rhythm) due to its self-contained enteric nervous system.

This structure consists of connective tissue covered by a simple squamous epithelium, called the mesothelium, which reduces frictional forces during digestive movements.

They blend into the surrounding tissue and are fixed in position (for example, the retroperitoneal section of the duodenum usually passes through the transpyloric plane).

This is called esophagitis, gastritis, duodenitis, ileitis, and colitis depending on the parts affected.

Crohn's disease may produce inflammation in all layers in any part of the gastrointestinal tract and so can result in transmural fistulae.

[7] Segmental or diffuse gastrointestinal wall thickening is most often due to ischemic, inflammatory or infectious disease.