The human digestive system consists of the gastrointestinal tract plus the accessory organs of digestion (the tongue, salivary glands, pancreas, liver, and gallbladder). Digestion involves the breakdown of food into smaller and smaller components, until they can be absorbed and assimilated into the body. The process of digestion has three stages: the cephalic phase, the gastric phase, and the intestinal phase. The first stage, the cephalic phase of digestion, begins with secretions from gastric glands in response to the sight and smell of food.
Gastrointestinal bleeding (GI bleed), also called gastrointestinal hemorrhage (GIB), is all forms of bleeding in the gastrointestinal tract, from the mouth to the rectum. When there is significant blood loss over a short time, symptoms may include vomiting red blood, vomiting black blood, bloody stool, or black stool. Small amounts of bleeding over a long time may cause iron-deficiency anemia resulting in feeling tired or heart-related chest pain. Other symptoms may include abdominal pain, shortness of breath, pale skin, or passing out.
Blood in stool or rectal bleeding looks different depending on how early it enters the digestive tract—and thus how much digestive action it has been exposed to—and how much there is. The term can refer either to melena, with a black appearance, typically originating from upper gastrointestinal bleeding; or to hematochezia, with a red color, typically originating from lower gastrointestinal bleeding.
Haematochezia is the passage of fresh blood through the anus path, usually in or with stools (contrast with melena). The term is from Greek αἷμα ("blood") and χέζειν ("to defaecate"). Hematochezia is commonly associated with lower gastrointestinal bleeding, but may also occur from a brisk upper gastrointestinal bleed. The difference between hematochezia and rectorrhagia is that, in the latter, rectal bleeding is not associated with defecation; instead, it is associated with expulsion of fresh bright red blood without stools.
Melena or melaena refers to the dark black, tarry feces that are associated with upper gastrointestinal bleeding. The black color and characteristic strong odor are caused by hemoglobin in the blood being altered by digestive enzymes and intestinal bacteria. Iron supplements may cause a grayish-black stool that should be distinguished from melena, as should black coloration caused by a number of medications, such as bismuth subsalicylate (the active ingredient in Pepto-Bismol), or by foods such as beetroot, black liquorice, or blueberries.
The duodenum (duː'wɑːdɪnəm , duːoʊ'diːnəm ) is the first section of the small intestine in most higher vertebrates, including mammals, reptiles, and birds. In mammals it may be the principal site for iron absorption. The duodenum precedes the jejunum and ileum and is the shortest part of the small intestine. In humans, the duodenum is a hollow jointed tube about long connecting the stomach to the middle part of the small intestine. It begins with the duodenal bulb and ends at the suspensory muscle of duodenum.
Hematemesis is the vomiting of blood. It can be confused with hemoptysis (coughing up blood) or epistaxis (nosebleed), which are more common. The source is generally the upper gastrointestinal tract, typically above the suspensory muscle of duodenum. It may be caused by ulcers, tumors of the stomach or esophagus, varices, prolonged and vigorous retching, gastroenteritis, ingested blood (from bleeding in the mouth, nose, or throat), or certain drugs. Hematemesis is treated as a medical emergency, with treatments based on the amount of blood loss.
The small intestine or small bowel is an organ in the gastrointestinal tract where most of the absorption of nutrients from food takes place. It lies between the stomach and large intestine, and receives bile and pancreatic juice through the pancreatic duct to aid in digestion. The small intestine is about long and folds many times to fit in the abdomen. Although it is longer than the large intestine, it is called the small intestine because it is narrower in diameter.
Upper gastrointestinal bleeding is gastrointestinal bleeding in the upper gastrointestinal tract, commonly defined as bleeding arising from the esophagus, stomach, or duodenum. Blood may be observed in vomit or in altered form as black stool. Depending on the amount of the blood loss, symptoms may include shock. Upper gastrointestinal bleeding can be caused by peptic ulcers, gastric erosions, esophageal varices, and rarer causes such as gastric cancer.
The jejunum is the second part of the small intestine in humans and most higher vertebrates, including mammals, reptiles, and birds. Its lining is specialized for the absorption by enterocytes of small nutrient molecules which have been previously digested by enzymes in the duodenum. The jejunum lies between the duodenum and the ileum and is considered to start at the suspensory muscle of the duodenum, a location called the duodenojejunal flexure. The division between the jejunum and ileum is not anatomically distinct.
