Anatomy of GI Tract
During digestion, food is eliminated from the stomach after it travels through the pharynx, esophagus, stomach, and intestines to the rear of the body. The digestive tract is supported by a variety of accessory organs that secrete enzymes that break down food into its constituent nutrients. Salivary glands, liver, pancreas, and gallbladder are heavily involved in digestive function. During peristaltic movements of the muscular walls, food is propelled along the GIT.As it breaks down foods into nutrients, the gastrointestinal tract provides the body with energy. In order to be mechanically processed, food must be ingested first and moistened afterward. Another important component of digestion is the breakdown of fats, proteins, and carbohydrates in the stomach and small intestine, where chemical reactions happen. In the small intestine, smaller molecules are absorbed across the epithelium and are then transported to the bloodstream. Reabsorbing excess water is a key function of the large intestine. By way of defecation (passing of feces), the body excretes undigested material and secreted waste products.
When the gastrointestinal tract is afflicted by a disease or disorder, it cannot carry out these functions. A patient may also experience nausea, vomiting, diarrhea, malabsorption, constipation, or obstruction. Having digestive problems is very common.
Basic structure
The epithelium is the layer of cells lining the gastrointestinal tract. A tube in the mouth and the anus is in continuous communication with the outside world and is considered external to the body. The track has a similar structure with regional variations, even though each segment has its own unique functions.There are four layers to the wall:
Mucosa
Gastritis is the inflammation of the mucous membrane lining the inside of the stomach. Columnar epithelial cells covering the mucosa always secrete mucus. Mucus from the stomach serves as a lubricant that facilitates food movement within the stomach cavity as well as a protective layer that protects the stomach cavity's lining epithelium. Protective layers protect the stomach from being digested by its own protein-lyzing enzymes, and they are made possible by the secretion of bicarbonate from the underlying mucosa into the surface layer. Immediately adjacent to the epithelium, there is neutral pH7 (hydrogen ion concentration) and the pH level at the luminal level is more acidic (pH2). With the aid of a magnifying glass, one can observe small pits, known as foveolae gastrique, on the surface epithelium of the stomach. Approximately 58,000 to 65,000 gastric pits are found per square inch (59,000 to 100 pits) of the surface epithelium. Within each gastric pit, three to seven gastric glands secrete their contents. A layer of mucosa lies underneath the muscularis mucosae, which connects the mucosa to the stomach muscles.Submucosa
In the submucosa, which surrounds the muscles, fat, fibrous connective tissue, large vessels, and nerves are found. This nerve plexus is located at its outer margin and is called the submucosal plexus of the Meissner plexus.Muscularis Externa
Myenteric plexus separates the inner circle and outer longitudinal layer of quadriceps muscles. The food is mechanically broken down by contracting these muscles, then moved within the lumen by the movement of these muscles.Serosa/mesentery
The outer layer of the GIT consists of fat and mesothelium.Following are the components of the GI system:
- Oral cavity
- Stomach
- Large intestine
- Liver
- Oesophagus
- Gall bladder
- Salivary glands
- Small intestine
- Pancreas
Anatomy of stomach
Within the upper part of the abdominal cavity, just below the diaphragm, the stomach resides primarily under the diaphragm. There are three sections to the stomach:Cardia
The cardiac orifice (the opening from the esophagus into the stomach) is the area of the stomach surrounding the Cardioesophageal junction. Cardi-oesophageal junctional tumors usually affect the stomach.Fundus
In the left upper corner of the heart is an enlarged portion known as the fundus.Body of stomach
The corpus, or the body of the stomach, is the central portion.Pyloric antrum
Antrums are located below the duodenum, either distal or lower in the stomach. Pyloric sphincter controls the movement of chyme into the duodenum through the opening between the stomach and small intestine. A smaller omentum is situated near the abdominal wall near the stomach. The greater omentum also connects the stomach to the transverse colon and is located between the liver, spleen, and diaphragm.Functions of stomach
- During the period of 2 hours or more, food passes from the esophagus to the stomach and is temporarily stored.
- In the stomach, contractions, and relaxations of the muscle layers mix and break down food.
- complete the digestion of food.
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Ankur Choudhary is India's first professional pharmaceutical blogger, author and founder of pharmaguideline.com, a widely-read pharmaceutical blog since 2008. Sign-up for the free email updates for your daily dose of pharmaceutical tips.
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