The parathyroid gland is located on the posterior surface of the thyroid gland and consists of four glands, two superior glands derived from the fourth pharyngeal pouch and two inferior glands from the third pouch. The gland contains two cell types: principal cells that secrete parathyroid hormone to increase blood calcium levels by acting on bones and kidneys, and oxyphil cells of unknown function.

1. PARATHYROID GLAND
Dr. R. Kalliecharan

2. Location and Histology
• Is located on posterior surface of
Thyroid
• Composed of 1 pr of superior glands
(which arise from endoderm of 4th
pharyngeal pouch) and 1 pr of inferior
glands (from 3th pharyngeal pouch ).
• Histology---2 cell types

3. Cell Types
• 1) Principal (Chief) cells secrete PTH
• ( parathyroid hormone)
• 2) Oxyphil cells –function unknown,
has acidophilic cytoplasm, many mito.
And pyknotic nuclei.

6. Chief Cells
• Low Ca++ in blood causes PTH secretion from
chief cells
• PTH acts on osteoclasts via osteoblasts to
increase Ca++ in blood from bone
• PTH acts on Kidneys to(a) ↑ Ca++ in blood
• And(b) cause the formation of Vit D (calcitriol)
which ↑ intestinal absorption of Ca++