Intestinal absorption minerals, discussion

The absorption of many minerals is affected by other compounds present in the intestinal lumen. As discussed in section 4.5.1, a number of reducing compounds can enhance the absorption of iron, and a number of chelating compounds enhance the absorption of other minerals. For example, zinc absorption is dependent on the secretion by the pancreas of a zinc-binding hgand (tentatively identified as the tryptophan metabolite picolinic acid). Failure to synthesize and secrete this zinc-binding ligand as a result of a genetic disease leads to the condition of acrodermatitis enteropathica— functional zinc deficiency despite an apparently adequate intake. 

In discussing the absorption of minerals, especially In the context of their biological availability. It Is Important to clarify three terms for the subdivisions of the absorptive process uptake refers to the entrance of the nutrient Into the mucosal cell from the intestinal lumen transfer refers to the passage of the nutrient out of the mucosal cell and transport refers to the removal of the nutrient from the vicinity of the Intestine to other parts of the organism. All three processes are essential for a dietary component, such as zinc, to achieve a nutritional role for the the organism. From the array of mechanisms thought... 

Now that the mechanism of action of vitamin D has been discussed, it will be easier to understand the morbid anatomy and the clinical aspect of rickets [18, 19]. Vitamin D deficiency leads to low calcium absorption through the intestinal tract, and thereby to deficient mineralization of bone matrix. When rickets develops in the young child, all bones soften with typical malformation. The long bones are curved, especially the tibia, which often acquires a saber-blade shape. The thorax is distorted as a result of scoliosis and kyphosis and enlargement of the lower part of the thoracic cage. The pelvic bones are often underdeveloped and lead to narrowing of the pelvic lumen, which may be responsible for dystocia of the female patient. The bones of the skull are soft and flattened and present an appearance described as crania tabes. 

There is rapid turnover of the cells of the intestinal mucosa epithelial cells proliferate in the crypts, alongside the cells that secrete digestive enzymes, and migrate to the tip of the villus, where they are shed into the lumen. The average life of an intestinal mucosal epithelial cell is about 48 hours. As discussed in section 4.5, this rapid turnover of epithelial cells is important in controlling the absorption of iron, and possible other minerals. 

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