What is the most common method for absorption of electrolytes?

Question

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Answer 1

***************Iron **************************
http://www.siumed.edu/mrc/research/nutrient/gi42sg.html
Iron balance differs from that of other trace elements in that it is regulated primarily by absorption, not excretion. Because the body's ability to excrete iron is very limited, intestinal iron uptake is closely restricted to about 1 mg, which is the amount usually excreted daily in the urine and feces. This is a small fraction (0.03%) of the total body iron content. Relatively large amounts are lost, of course, during menstruation. The exact amount absorbed is determined by many factors, which may be classified as luminal, epithelial and corporeal.
Usually, more than 90% of the fluid entering the small intestine is absorbed, so that about one litre reaches the large intestine. There, further absorption occurs, only 100 to 200 millilitres of water being excreted each day in formed stools. Any change in the two-directional flow of water and electrolytes in the small intestine (i.e., increased secretion, decreased absorption, or both) results in either reduced net absorption or net secretion and causes an increased volume of fluid to enter the large intestine. When this exceeds its limited absorptive capacity, diarrhoea occurs.