Where is the duodenum located?

The duodenum is the most critical part of the human body. It is located between the abdomen and stomach. The duodenum is the largest and deepest part of the small intestine. The duodenum plays a critical role. If there is a disease in the duodenum, it will easily lead to some digestive problems, which is very harmful to the human body. Pay more attention to intestinal health.

Where is the duodenum located?

The duodenum is an organ between the stomach and the jejunum in the human body. The length of the duodenum in an adult is 20 to 25 cm, with a diameter of 4 to 5 cm. It is close to the posterior abdominal wall and is the shortest, largest, deepest and most fixed segment of the small intestine. The duodenum is C-shaped, enclosing the head of the pancreas, and can be divided into four parts: the bulbous part, the descending part, the horizontal part, and the ascending part.

composition

Observation specimen: Cross-section of duodenum (HE staining) The mucosa was stained purple-red by naked eye, and outward there were submucosa, muscularis and adventitia. The mucosa and submucosa protruded into the lumen to form annular folds.

Low-power and high-power observations show that the duodenal wall is divided into four layers from inside to outside.

1. Mucous membrane:

① Epithelium: It is a single-layer columnar epithelium, mainly composed of columnar cells, containing a small amount of goblet cells and endocrine cells. The free surface has a thin layer of red-stained linear structure as the striated border.

② Lamina propria: It is connective tissue, containing a large number of intestinal glands, abundant capillaries, lymphatic capillaries, nerves, scattered smooth muscle cells and lymphatic tissue. The small intestinal glands are single tubular glands that open between adjacent villi. The glandular epithelium is connected to the villus epithelium, and the cell composition is similar to that of the small intestinal epithelium. There are groups of Paneth cells distributed at the bottom of the small intestinal glands. Not easily visible in the specimen.

③ Mucosal muscularis: It is smooth muscle. Are the cross sections of muscle cells the same and how are they arranged? Small intestinal villi: It is a leaf-like structure formed by the lamina propria and epithelium protruding into the intestinal cavity. The mass-like structure free in the intestinal cavity is the cross section of the villi. Compared with the small intestinal glands, what are the characteristics of the villi? In the center of the villi, a larger lumen can be seen. The central milky duct composed of a single layer of endothelium is the capillary lymphatic vessel. There are scattered smooth muscle bundles around the duct.

2. Submucosa:

It is loose connective tissue containing larger blood vessels, lymphatic vessels and submucosal nerve plexus. The duodenum also contains mucous duodenal glands. The glandular epithelial cells are conical or columnar, the cytoplasm is stained blue or hollow reticular, the nucleus is oblate and close to the base, the alveolar cavity is small and irregular, and the duct passes through the mucosal muscle and opens at the bottom of the small intestinal gland or between adjacent villi. 3) Muscle layer: There are two layers of smooth muscle, the inner circular and the outer longitudinal. What are the sections on the cross section? Can the intermuscular nerve plexus be found in the connective tissue between the two layers of muscle?

3. Outer membrane:

It is a serous membrane composed of a thin layer of loose connective tissue and mesothelium. The small intestine (Smallintestine) starts from the pylorus at the top and connects to the cecum at the bottom. It is 5 to 7 meters long in adults and is divided into three parts: the duodenum, the jejunum, and the ileum. The duodenum is located between the stomach and the jejunum. Both the pancreatic duct and the common bile duct open into the duodenum. Therefore, it receives the infusion of gastric juice, pancreatic juice and bile, so the digestive function of the duodenum is very important. The duodenum is C-shaped, enclosing the head of the pancreas, and can be divided into four parts: the bulbous part, the descending part, the horizontal part, and the ascending part.

4. Ball Department:

The duodenal bulb, also known as the upper part, is about 5 cm long, starting from the pylorus of the stomach and moving to the right rear. At the posterior and inferior part of the gallbladder neck, it makes a sharp turn to become the descending part, and the turning point is the superior duodenal flexure. The duodenal bulb is a section of intestine about 2.5 cm near the pylorus. It has thin walls, smooth mucosal surface, and no or very few annular folds. This section is called the duodenal bulb. It is a high-incidence site for duodenal ulcers. However, in clinical statistics, duodenal ulcers will not turn into cancer.

5. Descending part:

The descending part of the duodenum is the second part of the duodenum, which is about 7-8 cm long. It descends from the superior duodenal flexure along the inner edge of the right kidney to the level of the third lumbar vertebra, bends to the left, and the turning point is the inferior duodenal flexure. The left side of the descending part is close to the head of the pancreas. The mucosa of this part has many annular folds. The common bile duct runs along the outside of the posterior inner wall, causing the mucosa to form a longitudinal bulge that is slightly convex toward the intestinal cavity, which is called the longitudinal wall of the duodenum. The lower end of the longitudinal fold is a round protrusion called the major duodenal papilla, which is the common opening of the common bile duct and pancreatic duct. The common bile duct and pancreatic duct form the hepatopancreatic ampulla here. There is a pot valve near the major duodenal papilla, which can close the common bile duct or pancreatic duct and cause corresponding diseases. Slightly above the major papilla, the minor duodenal papilla can sometimes be seen, which is the opening of the accessory pancreatic duct.