Parathyroid Gland
What regulates parathyroid hormone?
Blood calcium levels - NOT the pituitary gland.
Small, polygonal cells with a centrally located nucleus, about the size of a RBC.
Chief (principal) cells
the more numerous of the cells, and are responsible for regulating the synthesis, storage and secretion of large amounts of PTH
Chief (principal) cells
Each parathyroid gland is surrounded by
a thin connective tissue capsule that separates it from the thyroid. called the STROMA
what color are the parathyroid glands?
dark tan to yellowish
Shape and arrangement of parathyroid glands
ellipsoid, a few millimeters in diameter, and arranged in two pairs constituting the superior and inferior parathyroid glands.
The glands receive their blood supply from
the inferior/superior thyroid arteries. Networks of fenestrated blood capillaries are found throughout.
The septae are called
trabeculae
What is the function of the oxyphilic cells?
We don't know - Function UNKNOWN.
The parenchyma, or functional tissue of the parathyroid gland is made of what types of cells?
1) Chief (principal) cells 2) Oxyphilic Cells
Size of a parathyroid gland
6x1x2mm
The connective tissue is more evident in the adult, with the development of fat cells that increase with age and ultimately consistute as much as
70% of the gland
Adipose Tissue which may be up to
70% of the gland in aged individuals
What is the function of parathyroid hormone?
Acts to INCREASE blood calcium levels
Why must care be taken during a thyroidectomy?
Care must be taken during thyroidectomy to leave some functioning parathyroid tissue. If the glands are totally removed, death will ensue because muscles, including the laryngeal and other respiratory muscles, go into tetanic contraction as the blood calcium level falls.
Where are parathyroid glands found?
Embedded in the posterior surface of the thyroid gland
How do the oxyphilic cells stain?
Heterochromatic nucleus with intensely eosinophilic cytoplasm due to large #s of mitochondria. NO secretory grancules.
Function of the parathyroid gland
Increase blood Ca++ via Parathyroid Hormone (NB:opposite of calcitonin from the Clear Cells)
Oxyphilic Cells
Large cells found singly or in clumps
Chief (principal) cells
Major cell type; arranged in cords Secrete Parathyroid hormone (PTH)
What does the parathyroid gland produce?
One hormone - the parathyroid hormone
a minor portion and are not known to have a secretory role
Oxyphilic Cells
are found singly or in small clusters; the cells are more rounded, considerably larger than the principal cells
Oxyphilic Cells
Gross Anatomy of the Parathyroid Gland
Two pairs (superior/inferior on posterior surface of thyroid Embedded in CT capsule of Thyroid Ellipsoid, 6x1x2mm Number and location may vary
PTH acts on
osteoclasts, renal tubule cells, indirectly on intestinal epithelial cells
small endocrine glands closely associated with the thyroid
parathyroid glands
Septa extend from the capsule into the gland to divide it into
poorly defined lobes
Parathyroid gland is derived from
portions of 3rd and 4th pharyngeal pouches. Parathyroid glands develop from the endodermal cells derived from the third and fourth pharyngeal pouches.
what cells are more numerous?
principal cells