General structure of the digestive tract wall

Many people who have irregular diets will suffer from stomach problems, and among the symptoms of stomach problems, the most common is indigestion. Many cases of indigestion in the human body are due to problems with the digestive tract, which requires everyone to understand the internal structure of our body, especially the structure of the digestive tract wall. So, what is the general structure of the digestive tract wall?

Digestive tract

The digestive system consists of the digestive tract and digestive glands. Its main function is to physically and chemically digest food, breaking down large molecules into small molecules such as amino acids, monosaccharides, glycerides, etc. After absorption, it meets the body's growth and metabolism needs. The digestive tract is a continuous tube from the mouth to the anus, which is divided into the mouth, pharynx, esophagus, stomach, small intestine and large intestine. The wall structures of these organs have certain common stratification patterns, and each has its own characteristics that are adapted to its function.

1. General structure of the digestive tract

The digestive tract (except the oral cavity and pharynx) is divided into four layers from inside to outside: mucosa, submucosa, muscularis, and adventitia.

(I) Mucous membrane

The mucosa (tunica mucosa) is composed of epithelium, lamina propria and muscularis mucosa. It is the part with the greatest structural differences and the most important function among all sections of the digestive tract.

1. Epithelium The type of epithelium varies depending on the location. The two ends of the digestive tract (mouth, pharynx, esophagus and anus) are lined with stratified squamous epithelium, which mainly serves the protective function; the rest of the body is lined with single-layer columnar epithelium, which mainly serves the digestion and absorption function. The epithelium is connected to the glands within the tube wall.

2. Lamina propria The lamina propria is a loose connective tissue that contains many cells and fibers and is rich in blood vessels and lymphatic vessels. The gastrointestinal lamina propria is also rich in glandular or lymphoid tissue.

3. Muscularis mucosa The muscularis mucosa is a thin layer of smooth muscle. Its contraction can make the mucosa active, promote the discharge of glandular secretions and blood circulation in the lamina propria, and facilitate the absorption of substances.

(ii) Submucosa

The submucosa (tela submucosa) is composed of loose connective tissue and contains larger blood vessels and lymphatic vessels. In the submucosal layer of the esophagus and duodenum are the esophageal glands and duodenal membranes, respectively. There is also a submucosal plexus in the submucosal layer, which is composed of multipolar neurons and unmyelinated nerve fibers, which can regulate the contraction of mucosal muscles and the secretion of glands. The mucosa and submucosa in the esophagus, stomach, and small intestine protrude into the lumen to form plicas.

(III) Muscle layer

Except for the muscular layer (tunica muscularis) at the upper esophagus and anus, which is skeletal muscle, most of the rest is smooth muscle. The muscular layer is generally divided into two layers: the inner circular layer and the outer longitudinal layer, between which there is the intermuscular nerve plexus, which has a structure similar to the submucosal nerve plexus and can regulate the movement of the muscular layer.

(IV) Outer membrane

The outer membrane (tunica adventitia) is composed of a thin layer of connective tissue called fibrosa. It is mainly distributed in the esophagus and the terminal part of the large intestine and has no obvious boundary with the surrounding tissue. The serosa is composed of a thin layer of connective tissue and mesothelium. It is found in the stomach, most of the small intestine and large intestine within the peritoneum. Its surface is smooth, which facilitates gastrointestinal activity.