The most structurally different and functionally important part of the digestive tract.

composition

Dense connective tissue connecting mucosa and muscle layer

Contains arterioles, venules and lymphatic vessels

There are esophageal glands and duodenal glands in the submucosa of the esophagus and duodenum, respectively.

The mucosa and part of the submucosa of the esophagus, stomach, small intestine, and large intestine protrude into the digestive tract to form folds - expanding the surface area

Except for the upper part of the esophagus and the lower part of the anal canal, which are skeletal muscles, most of the rest are smooth muscles.

Generally divided into two layers: inner ring and outer longitudinal layer.

The stomach is thick and can be divided into three layers: internal oblique, middle ring, and external longitudinal layers.

fiber membrane

Serosa

Predisposed sites for esophageal cancer

epithelium

lamina propria

muscularis mucosa

loose connective tissue

Esophageal gland ducts penetrate the mucosa and open into the esophageal lumen

More lymphocytes can be seen around the esophageal glands, and lymph nodes are occasionally seen.

inner loop

outside vertical line

The upper third of the esophagus is skeletal muscle

The lower third is smooth muscle

The middle third is a mixture of skeletal muscle and smooth muscle

The circular muscles at the upper and lower ends of the esophagus thicken to form the upper and lower esophageal sphincters.

fiber membrane

There are criss-crossing shallow grooves on the surface, dividing the mucosa into many gastric cells.

The surface is covered with irregular holes, called gastric pits

epithelium

lamina propria

muscularis mucosa

finer connective tissue

Contains larger blood vessels, lymphatic vessels and nerves

internal diagonal

Central

outside vertical line

Serosa

epithelium

lamina propria

muscularis mucosa

There are larger blood vessels and lymphatic vessels in the submucosal connective tissue

The submucosal layer of the duodenum contains biductal and alveolar duodenal glands, also known as Brenner's glands

Small intestinal epithelial and glandular secretions are called intestinal fluid, which is slightly alkaline

Except for the posterior wall of the duodenum, which is fibrous membrane, the rest is serosa

Mucous membrane

submucosa

Muscle layer

adventitia

The lumen is small and irregular

The lamina propria contains abundant lymphoid tissue, forming lymphatic nodules that protrude into the submucosa, leaving the muscularis mucosa incomplete.

Important organ of mucosal immune function

Muscle layer

serous membrane

anal column

At the dentate line, the single-layer columnar epithelium suddenly changes into non-keratinized stratified squamous epithelium, and the intestinal glands and mucosal muscles disappear.

Below the white line is keratinized stratified squamous epithelium, which contains more melanin.

Apocrine and sebaceous glands are present in the lamina propria

The connective tissue of the submucosa contains a rich venous plexus

Muscle layer