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Excretion is elimination of metabolic waste, which is an essential process in all organisms. In vertebrates, this is primarily carried out by the lungs, kidneys, and skin. [1] This is in contrast with secretion, where the substance may have specific tasks after leaving the cell.
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.
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 ...
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.
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]
Death has been known to occur in cases where defecation causes the blood pressure to rise enough to cause the rupture of an aneurysm or to dislodge blood clots (see thrombosis). Also, in releasing the Valsalva maneuver blood pressure falls; this, coupled with standing up quickly to leave the toilet, can result in a blackout. [citation needed]
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Hematochezia is similarly the passage of feces that is bright red due to the presence of undigested blood, either from lower in the digestive tract, or from a more active source in the upper digestive tract. Alcoholism can also provoke abnormalities in the path of blood throughout the body, including the passing of red-black stool. Hemorrhoids ...