Title: Digestive system – Histology
Headings: 12
Digestive system

12 Digestive system
Four layers of digestive tract walls
Mucosa
Submucosa
Muscularis externa
Adventitia
Regional histology of the digestive tract
Esophagus
Stomach
Small intestine
Large intestine
Region
Histological characteristics
Esophagus
Stomach
Small Intestine
Large Intestine

Content: Gastric glands and gastric pits of gastric mucosa. Small intestine
The small intestine is a long tube that extends from the stomach to the junction with the large intestine (a.k.a colon.) The major functions of the small intestine are digestion, secretion, and absorption. The small intestine is divided into three segments: duodenum,
jejunum
ileum. The mucosa of the small intestine has some adaptations to the functions it serves. It is heavily creased into the structures that increase the surface area where the nutrients are digested and absorbed. These adaptations include intestinal folds called the plicae circulares, villi, and microvilli. The plicae circulares are folds of mucosa and submucosa that extend into the intestinal lumen. They encircle the entire intestine and are visible without a microscope, so they will not be discussed here.