Digestive System Organs: Relationships

A.    Relationship of Digestive Organs to the Peritoneum

1.     The visceral peritoneum covers the external surfaces of most of the digestive organs, and the parietal peritoneum lines the body wall of the abdominopelvic cavity.

2.     The peritoneal cavity is located between the visceral and parietal peritoneum and is filled with serous fluid.

3.     Mesentery is a double layer of peritoneum that extends to the digestive organs from the body wall. It allows blood vessels, lymphatics, and nerves to reach the digestive organs, and holds the organs in place as well as stores fat.

4.     Retroperitoneal organs are found posterior to the mesentery, lying against the dorsal abdominal wall [most of pancreas and parts of the large intestine].

B.    The splanchnic circulation serves the digestive system and includes those arteries that branch off the abdominal aorta to serve the digestive organs and the hepatic portal circulation [hepatic, splenic, and left gastric arteries of the celiac trunk and the superior &inferior mesenteric arteries]

C.    Histology of the Alimentary Canal

1.     Mucosa is the innermost, moist, epithelial membrane that lines the entire digestive tract. It secretes mucus, digestive enzymes, and hormones; absorbs digestive end products into the blood; and protects against infectious disease.

2.     Submucosa is a moderately dense connective tissue layer containing blood and lymphatic vessels, lymphoid follicles, and nerve fibers.

3.     Muscularisexterna typically consists of smooth muscle and is responsible for peristalsis and segmentation.

4.     Serosa, the protective outer layer of the intraperitoneal organs, is the visceral peritoneum.

D.    The alimentary canal has its own nerve supply made up of enteric neurons that communicate widely with each other to regulate digestive activity.