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The gastrointestinal tract (GI tract, digestive tract, alimentary canal) is the tract or passageway of the digestive system that leads from the mouth to the anus/cloaca.The GI tract contains all the major organs of the digestive system, in humans and other animals, including the esophagus, stomach, and intestines.
The digestive system is supplied by the celiac artery. The celiac artery is the first major branch from the abdominal aorta , and is the only major artery that nourishes the digestive organs. There are three main divisions – the left gastric artery , the common hepatic artery and the splenic artery .
His own opinion was that digestion was aided by a chemical reagent, or "ferment", within the body, such as inside the stomach. Harré suggests that van Helmont's theory was "very near to our modern concept of an enzyme". [10] Van Helmont proposed and described six different stages of digestion. [11]
Digestion is a form of catabolism that is often divided into two processes based on how food is broken down: mechanical and chemical digestion. The term mechanical digestion refers to the physical breakdown of large pieces of food into smaller pieces which can subsequently be accessed by digestive enzymes .
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.
Every day, seven liters of fluid are secreted by the digestive system. This fluid is composed of four primary components: ions, digestive enzymes, mucus, and bile. About half of these fluids are secreted by the salivary glands, pancreas, and liver, which compose the accessory organs and glands of the digestive system.
Digestive enzymes take part in the chemical process of digestion, which follows the mechanical process of digestion. Food consists of macromolecules of proteins, carbohydrates, and fats that need to be broken down chemically by digestive enzymes in the mouth , stomach , pancreas , and duodenum , before being able to be absorbed into the ...
The cephalic phase of digestion is the stage in which the stomach responds to the mere sight, smell, taste, or thought of food. About 20% of total acid secretion occurs before food enters the stomach.