Individuals who live in locations with limited exposure to sunlight can have abnormal bone development due to an inability to absorb calcium and phosphate ions from the small intestine. Why does a limited exposure to sunlight cause abnormal bone development?A. Cholecalciferol, or vitamin D3, is necessary for the normal absorption of calcium and phosphate ions. Vitamin D3 is made by cells in the epidermis due to exposure to sunlight. Without enough exposure to sunlight, the body won't produce enough vitamin D3B. People are more depressed in areas with limited sunlight, and depression can cause abnormal development of bones. C. People exercise less in areas where there is limited sunlight. This lack of exercise can cause abnormal development of bones. D. People sleep more in areas of limited sunlight.

A. Cholecalciferol, or vitamin D3, is necessary for the normal absorption of calcium and phosphate ions. Vitamin D3 is made by cells in the epidermis due to exposure to sunlight. Without enough exposure to sunlight, the body won't produce enough vitamin D3

Explanation:

Hydroxyapetite  is the organic mineral  in  the bone that maintain  the  mechanical strengthening of the bone, by interacting with collagen fibres.  Calcium and Phosphate ions  are the two major components of this  bone materials. Generally 90%of bone is calcium , while 80% is phosphate.  Phosphate stimulate growth of  Oesteocytes. And the latter is important for bone mineralization. Together they maintain bone mineralization and maintenance,thereby preventing bone resorption.

Absorption of  Ca and P. into the blood stream to reach the bones cells is conducted by Vit D. Dietary supply is not the only route through which  Vit D get to the blood stream. Exposure of the skin to UVB rays of the early morning sunlight is another route.

Vitamin D plays major  role in absorption of Ca and P in the body.

Vit. D is  naturally synthesized in humans when the skin is exposed to  early morning sunlight  (UVB). It is usually produce in inactive forms,and undergoes hydroxylation( i.e addition of hydroxyl group -OH) in the liver to  be biologically active .

Its active forms acts on the epithelial cells of the intestinal wall to facilitate calcium absorption into the blood stream  to reach the bone cells .it also stimulate absorption of Phosphate.

Since these two minerals ensures, mechanical strength, prevention of bone resorption,  there availability in the bone must be maintained by Vit, D supply from exposure to sunlight.

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