Submitted by: Submitted by kag0m37
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Category: Science and Technology
Date Submitted: 08/16/2011 08:25 AM
Parathyroid Gland
Location & Definition
* Small yellowish brown, ovoid structures
* 6 x 3-4 x 1-2 mm
* Weighs 50mg
* Related posterior border of thyroid gland within its fascial (fibrous) capsule
* Stimulates the activityof osteoclasts
* Chief cells that produce parathyroid hormone/ parathormone
* parathyroid hormone/ parathormone
* Stimulates osteoclastic activity in bone thus, mobilizing bone calcium
* Increases calcium levels in blood
* Secretion of parathyroid hormone is controlled by calcium levels in the blood
* Stimulates absorption of dietary calcium from small intestine
* Also, stimulates reabsorption of calcium in proximal convulated tubules of the kidney
* Strongly diminishes the reabsorption of phosphate in the proximal tubules of kidney disease
* 4 in number = 2 superior, 2 inferior
Embryological Development
* Endoderm
* 3rd and 4th pharyngeal arches/pouch
* Proliferation of entodermal cells of the 3rd pharyngeal arch/pouch = inferior parathyroid gland pair (Parathyroid III)
* Proliferation of entodermal cells of the 4th pharyngeal arch/pouch = superior parathyroid gland pair (Parathyroid IV)
* Earliest stages, consists of solid mass of clear cells (chief cells)
* Late Childhood, oxyphil cells (acidophilic) appear
* Oxyphil cells – thought to be non-functioning chief cells
* Conditions
* Absence and Hypoplasia of Parathyroid Glands
* Incomplete development or agenesis is demonstrated in individuals with idiopathic hypoparathyroidism.
* Ectopic Parathyroid Glands
* Finding of the parathyroid tissue in the superior mediastinum of the thorax
* If the parathyroid glands remain attached to the thymus, they may be pulled inferiorly into the lower part of the neck or thoracic cavity.
* Explains the variable position of the inferior parathyroid glands in...