Calcium Balance and Reproduction I

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Calcium Balance and Reproduction I

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University of Southern California
Bisc 307l - General Physiology
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BISC 307L 1st Edition Lecture 19 Current Lecture Calcium Balance  Hormones that Regulate Body Calcium o o There are 3 that regulate  1. Parathyroid hormone +  released from the parathyroid glands embedded in posterior view of thyroid gland  essential for life  *function to raise plasma Ca2+  2. Calcitriol (or vitamin D3) +  steroid hormone  made from vitamin D (made in skin or dietary)  liver cells take this vitamin D and convert it to intermediate and kidney takes this intermediate and converts it into calcitriol  *raises plasma Ca2+  3. Calcitonin (-)  made by C cells in the thyroid gland  *lowers plasma Ca2+  Calcium Balance o o Top white area: small intestine  Source of new calcium added to the body (by absorption of dietary calcium)  Two fates:  Stays in small intestine and excreted  Or absorbed into extracellular tissue o Bone at left:  Bone is important reservoir for calcium  Calcium can be taken from the EC fluid and deposited in the bones  This causes new bone formation- the cells that do this are called osteoblasts  Osteoclasts break down the bone and liberate calciummoves calcium back into ECF o Right: Kidney  Calcium is filtered in the kidney tubule  Can be not reabsorbed and passes in the urine or it can be reabsorbed and put back into the ECF o Parathyroid hormone: 3 ways to raise calcium plasma  1.strongly stimulates bone reabsorption (activity of osteoclasts in freeing calcium  2. Reabsorption of calcium back into the blood in kidney  this also lowers plasma phosphate

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