Organ Name: Stomach (gastr-, gastro-)

Where it’s located: Upper left side of the abdomen.

What System: Digestive System

Main Function: The stomach is a hollow, muscular organ that is an enlarged pouch section of the digestive system, shaped like a comma. It is made of layers of connective tissue, blood vessels, muscle fibers, nerves, and mucous membrane.The upper part of the stomach curves upward toward the diaphragm, the stomach then narrows in its lower part to the small-intestine. Stomach lining is made up of visible folds that run toward the exit of the stomach, which allows liquids to quickly flow through. Microscopically speaking, the mucous membrane has tons of tiny glands, and each one creates digestive enzymes, hydrochloric acid, mucus, and bicarbonate.
Simply explained, it takes in food from the esophagus, breaks it down, and passes it to the small intestine in small-scale portions. Inside the largest part of the stomach, or the body, food is mixed and broken into smaller pieces by acidic gastric juice and enzymes. These gastric juices are made up of hydrochloric acid, digestive enzymes, and other substances that are needed to absorb nutrient, with about three to four liters of these juices produced per 24 hour period. Additionally, the muscles can move around food vigorously, which can crush and grind solid parts of food. After the pre-digestion phase, the food is released at the exit of the stomach through to the small intestine.

Protective Bodies: The lower part of the rib cage protects the stomach, especially from the dorsal side.

Germ Layer: Endoderm layer gives rise to the stomach.

Major Arteries, Veins, or Nerves: the left and right gastric arteries, the left and right gastroepiploic arteries, the common hepatic artery, left and right gastric veins, the vagus nerve, the celiac ganglia, submucous plexus, thoracic splanchnic nerves, and the myenteric plexus.

Intraperitoneal or Retroperitoneal: Intraperitoneal.

Diseases:
Gastric Adenocarcinoma: Most of the cancers that occur in the stomach are gastric adenocarcinomas, which mean that the cancer is affecting the glands of the stomach and could be malignant. The cancer spreads by infecting the surrounding tissues and blood vessels of the stomach and other abdominal structures. This means that the cancer can spread through the blood to sites that are further away, most commonly the lungs and liver.

Gastrointestinal Stromal Tumors: Relatively uncommon tumors of the gastrointestinal tract (GI). These tumors originate in early forms of cells called interstitial cells of Cajal, found in the wall of the gastrointestinal tract. These are cells that are part of the autonomic nervous system, which help regulate the digestion of food. Not all of these tumors are malignant, some can be benign and not grow or spread to other parts of the body, or may only grow in one site.

Carcinoid Tumors: Cancer that can originate in the lungs, or anywhere on the GI tract, including the stomach. A gastrointestinal carcinoid tumor is a neuroendocrine tumor that act like the cells they are derived from, and can release hormonal substances into the bloodstream. Typically, this release into the bloodstream is what causes symptoms, like fast heartbeat, wheezing, diarrhea, and flushing of the skin, to arise. This is typically known as carcinoid syndrome. However, in most people with carcinoid tumors, the hormonal release is never high enough to cause symptoms to become clear.