Lec13 - Calcium Homeostasis First Let’s Take a Look at...

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Unformatted text preview: Calcium Homeostasis First, Let’s Take a Look at This Diagram…… Homeostasis of Calcium Where Do I Get My Calcium? % 70 inorganic matrix composed of Calcium Salts in Hydroxyapatite Ca 10 (PO4) 6 (OH) 2 . The skeleton is resevoir for the minerals Calcium (and phosphorous). Resorption: the process of dissolving bone and releasing its minerals into the blood for other uses. The OSTEOCLAST secretes ACID PHOSPHATASE or sometimes HCL to digest bone matrix. Secreted by lysosomes. Resorption and Remodeling Resorption Osteoclasts do this using HCL and ACID PHOSPHATASE to dissove bone matrix Remodeling Ostoblasts do this Collagen fibers and hydroxyapatite matrix Its Role in Calcium Homeostasis VITAMIN D T The vitamin That Works Like a hormone How Does “D” Compare To Hormones? Vitamin D3 is not secreted by a classical endocrine gland, the active form of the hormone is released from the kidney and acts at distant sites or locally. Each of the forms of vitamin D is hydrophobic, and is transported in blood bound to carrier proteins. Only a very remains in a free form in the circulation and has a serum t1/2 of about 5 hours small proportion of vitamin D To Make Me D, Warm Me Up and Hydroxylate Me..3X! So..Exposure to Sun and Then, Fortified Foods….Give Us the D We Need How Does Vitamin D Facilitate Calcium Absorption in the Intestines?? IN THE INTESTINE It facilitates intestinal absorption of calcium, as well as stimulates absorption of phosphate and magnesium ions. In the absence of vitamin D, dietary calcium is not absorbed at all efficiently. Vitamin D stimulates the expression of a number of proteins involved in transporting calcium from the lumen of the intestine, across the epithelial cells and into blood. The vitamin D form, 1,25- dihydroxcholecalciferol [1,25(OH)2D3] , 1. stimulates the synthesis of the epithelial calcium channels in the plasma membrane calcium pumps , and 2. induces the formation of the calbindins . Vitamin D...
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Lec13 - Calcium Homeostasis First Let’s Take a Look at...

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