Phayrngeal Region Endocrine GlandsSlide 2Slide 3Slide 4Regulation of CaSlide 6Slide 7Slide 8Ca balanceSlide 10Slide 11Phayrngeal Region Endocrine GlandsParathyroidControl of Calcium HomeostasisPhayrngeal Region Endocrine Glands•Calcitonin–Produced in the intrafollicular cells of the thyroid–Produced by C-cells that are present in the thyroid, thymus, and parathyroid–Chemistry•Single chain protein 32 amino acids•Entire molecule required for biological activity3-12Phayrngeal Region Endocrine Glands•Calcitonin–Function•Lowers circulating Ca+•Targets bone, kidney, gut–Lowers ca by»Blocking absorption in the gut»Promoting its excretion in the kidney»Depositing it on the bone3-22Phayrngeal Region Endocrine Glands•Calcitonin•Regulation and secretion–No neural or neuroendocrine regulation–Calcium level is the most important regulator–Other hormones stimulate it CCK, gastrin3-22Regulation of Ca3-229.5 mg %11 mg %[Ca+]PTH CTNormal Ca levelPhayrngeal Region Endocrine Glands•Parathyroid•Anatomy•Embedded in surface of thyroid•Removal leads to death•Chief cells make PTH•Parathormone–Single chain 84 amino acids–Active core of 34 AA’s3-8Phayrngeal Region Endocrine Glands•Parathormone–Functions»Maintains Ca in body»Essential for life»Not stored, used readily»Supports all functions requiring Ca»muscular and nervous function»Bone structure»Blood clotting»2nd messenger systems»Egg shells3-22Phayrngeal Region Endocrine Glands•Parathormone–Mechanisms•Increase or decrease:» deposition in bone»Absorption in kidney and GI tract•Primary control–Calcitonin, vitamin D3, PTH•Secondary control–Adrenal steroids, thyroid3-22Ca balance•Total body Ca = 1.0-1.5Kg Ca–Tissues = 12g–Body fluids =1g (50% bound)–99% is in the bone!•Bone is a major Ca reservoir–1% readily availible–99% slowly availableCa balance•Pathways–Gut–Kidney–Liver–Ovary–Hormones•PTH, Calcitonin,Vitamin D3Ca balance•Vitamin D3•Works primarily on GI tract•Secondarily on the Bone–Source = Diet and Sunlight–PTH and Vitamin D are intimately related–Precursor is cholesterol–Fig 9.6,