Introduction to the Digestive System

Various Names

The contents of your digestive tract are not in your body.  The gastrointestinal tract is a tube within a tube design.  Think of how a doughnut has a hole in it. Now take that doughnut and expand it so that there’s a really long tube running down the center of it. That is the basicA solution with a pH above 7, having a lower concentration of H⁺ ions. design of your GI tract period. We can call it the GI tract for short when taking notes. You might also see it called the alimentary canal.

Primary GI Tract Organs

The mouthThe opening of the digestive tract where food enters and mastication begins., pharynxThe muscular passageway connecting the mouth to the esophagus and larynx., and esophagusThe muscular tube that transports food from the pharynx to the stomach via peristalsis. are all above the diaphragm and specialized for different roles. We have the stomach, a J-shaped organ. All of these guts in here are the small intestine. The large intestine completes the digestive system. The appendixA small, finger-like pouch attached to the cecum, thought to play a role in immune function. hangs off like an afterthought. The rectumThe final section of the large intestine, where feces are stored before elimination. serves as a waiting room. The anusThe terminal opening of the digestive tract through which feces are expelled. is the opening to the outside. Between these compartments or regions of the GI tract below the diaphragm are muscular valves called sphincters.  So, it’s not just like a slide at the amusement park.

Accessory GI Tract Organs

Digestive accessory organs are the organs that contribute secretions to the digestive tract. Food does not move through them, but they have a contribution.  We’ve met the pancreasA gland that produces digestive enzymes and hormones like insulin and glucagon. before in the endocrine systemThe organ system consisting of glands that secrete hormones to regulate body functions. for its hormone secreting islets.  Now, we consider the surrounding acinar cellsThe basic structural and functional units of life. that secrete digestive enzymesProteins that speed up chemical reactions in the body..  The liverA large organ that produces bile, detoxifies blood, and stores nutrients. is one of the largest organs in the body, by weight. Some people say that it rivals the skinThe body’s largest organ, providing protection and regulation., which is actually quite large. The liver generally produces bileA digestive fluid produced by the liver and stored in the gallbladder; it helps emulsify fats for di. This bile descends through the tract. It gets stored in the gallbladderA small organ beneath the liver that stores and releases bile into the small intestine.. It is then injected into the small intestine. The liver also cleanses blood from the digestive tract.

Peritoneum

Surrounding your guts is a serous membrane, much like the pericardiumThe membrane surrounding the heart. surrounding the heart. Visualizing the serous membrane surrounding all the differently shaped GI tract organs is complicated. This membrane is called the peritoneumThe membrane lining the abdominal cavity and organs.. It encloses the peritoneal cavities. Most of the GI organs are in the peritoneum. However, a few organs are retroperitoneal Referring to organs located behind the peritoneum, such as the kidneys and pancreas.. These include the pancreas, the upper small intestine (duodenumThe first section of the small intestine where most digestion occurs; it receives chyme, bile, and p), and the rectum.

Mesenteries and Omenta

The peritoneum, being a double membrane, forms sheets called mesenteries. The mesenteries act like an apron of fat, with blood vessels and lymph vessels running through them. Mesenteries feed the small intestine, colon, and stomach with blood vessels, nerves, and lymphatics. Mesenteries connected to the stomach are called omentumA fold of peritoneum that contains fat and blood vessels, providing protection and support to abdomi, while those attached to the large intestine are called mesocolonsExtensions of the peritoneum that anchor parts of the large intestine to the abdominal wall..The peritoneum, being a double membrane, forms sheets called mesenteries. The mesenteries act like an apron of fat, with blood vessels and lymph vessels running through them. Mesenteries feed the small intestine, colon, and stomach with blood vessels, nerves, and lymphatics. Mesenteries connected to the stomach are called omentum, while those attached to the large intestine are called mesocolons.