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Phayrngeal Region Endocrine Glands

Phayrngeal Region Endocrine Glands. Parathyroid Control of Calcium Homeostasis. Phayrngeal 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

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Phayrngeal Region Endocrine Glands

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  1. Phayrngeal Region Endocrine Glands Parathyroid Control of Calcium Homeostasis

  2. Phayrngeal 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 activity 3-12

  3. Phayrngeal 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 bone 3-22

  4. Phayrngeal Region Endocrine Glands • Calcitonin • Regulation and secretion • No neural or neuroendocrine regulation • Calcium level is the most important regulator • Other hormones stimulate it CCK, gastrin 3-22

  5. Regulation of Ca PTH CT Normal Ca level 3-22 9.5 mg % 11 mg % [Ca+]

  6. Phayrngeal 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’s 3-8

  7. Phayrngeal 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 shells 3-22

  8. Phayrngeal 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, thyroid 3-22

  9. Ca 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 available

  10. Ca balance • Pathways • Gut • Kidney • Liver • Ovary • Hormones • PTH, Calcitonin,Vitamin D3

  11. Ca 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, 9.8

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