Presentation
Parathyroid glands
There are four, oval-shaped endocrine glands embedded in the posterior surface of the thyroid gland.
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Two superior glands: located near the superior pole of the thyroid gland at the junction of cricoid and thyroid cartilages.
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Two inferior glands: located in the area between the inferior poles of the thyroid lobes and the superior mediastinum.
- Function: secretion of PTH in response to low calcium serum levels
- Arterial supply: Inferior thyroid arteries
- Venous drainage: Thyroid venous plexus
Different cells of the parathyroid glands:
- Chief cells: secretion of parathyroid hormone
- Oxyphil cells
- Adipocytes
Effects of parathyroid hormone (PTH):
Calcium:
- Increases blood calcium levels by directly stimulating osteoclasts to break down bone.
- Promotes calcium reabsorption by the kidneys
- Increases gastrointestinal calcium absorption by activating vitamin D
Phosphate
- Inhibits proximal tubular reabsorption of phosphorus