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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 human gastrointestinal tract consists of the esophagus, stomach, and intestines, and is divided into the upper and lower gastrointestinal tracts. [3] The GI tract includes all structures between the mouth and the anus , [ 4 ] forming a continuous passageway that includes the main organs of digestion, namely, the stomach , small intestine ...
English: The gastrointestinal tract, also called the digestive tract, alimentary canal, or gut, is the system of organs within multicellular animals that takes in food, digests it to extract energy and nutrients, and expels the remaining waste.
The gastrointestinal wall of the gastrointestinal tract is made up of four layers of specialised tissue. From the inner cavity of the gut (the lumen) outwards, these are the mucosa, the submucosa, the muscular layer and the serosa or adventitia. The mucosa is the innermost layer of the gastrointestinal tract.
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 .
In the human digestive system, a bolus (a small rounded mass of chewed up food) enters the stomach through the esophagus via the lower esophageal sphincter. The stomach releases proteases (protein-digesting enzymes such as pepsin ), and hydrochloric acid , which kills or inhibits bacteria and provides the acidic pH of 2 for the proteases to work.
Most of the studies of the digestive tract were done on animals and the results were compared to human structures. [ 7 ] The junction between the small intestine and the colon, called the ileocecal valve , is so small in some animals that it was not considered to be a connection between the small and large intestines.
Upper and lower human gastrointestinal tract. The human gastrointestinal tract is around 9 metres (30 feet) long. Food digestion physiology varies between individuals and upon other factors such as the characteristics of the food and size of the meal, and the process of digestion normally takes between 24 and 72 hours.