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Gastrointestinal physiology is the branch of human physiology that addresses the physical function of the gastrointestinal (GI) tract.The function of the GI tract is to process ingested food by mechanical and chemical means, extract nutrients and excrete waste products.
It breaks down both red and white blood cells that are spent. This is why it is sometimes known as the 'graveyard of red blood cells'. [23] A product of this digestion is the pigment bilirubin, which is sent to the liver and secreted in the bile. Another product is iron, which is used in the formation of new blood cells in the bone marrow. [5]
These intestinal lining cells can then either store the iron as ferritin, which is accomplished by Fe 2+ binding to apoferritin (in which case the iron will leave the body when the cell dies and is sloughed off into feces), or the cell can release it into the body via the only known iron exporter in mammals, ferroportin.
The dual function of excretory systems is the elimination of the waste products of metabolism and to drain the body of used up and broken down components in a liquid and gaseous state. In humans and other amniotes ( mammals , birds and reptiles ), most of these substances leave the body as urine and to some degree exhalation, mammals also expel ...
The transcellular (through the cells) and paracellular (between the cells) routes control the passage of substances between the intestinal lumen and blood. The barrier formed by the intestinal epithelium separates the external environment (the contents of the intestinal lumen ) from the body [ 6 ] and is the most extensive and important mucosal ...
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.The GI tract contains all the major organs of the digestive system, in humans and other animals, including the esophagus, stomach, and intestines.
The liver and kidneys clear many substances from the blood (for example, in renal excretion), and the cleared substances are then excreted from the body in the urine and feces. [6] Aquatic animals usually excrete ammonia directly into the external environment, as this compound has high solubility and there is ample water available for dilution.
Underlying the epithelium is the lamina propria, which contains myofibroblasts, blood vessels, nerves, and several different immune cells, and the muscularis mucosa which is a layer of smooth muscle that aids in the action of continued peristalsis and catastalsis along the gut.