The parathyroid glands are endocrine glands
30 mgs each
Lie on the posterior surface of the thyroid gland.
Two superior parathyroids lying about 1cm above the point where the inferior thyroid artery enters the thyroid.
The two inferior parathyroids lie 1cm below.
There is variation in the number and location of glands.
Situated within the fibrous capsule of the thyroid (intracapsular), or outside it (extracapsular).
Inferior thyroid artery
Superior thyroid artery
Thyroid ima artery
Venous drainage into the plexus of veins : the superior, middle and inferior thyroid veins.
Thyroid branches of the cervical sympathetic ganglia
The superior parathyroids are derived from
The inferior parathyroids from
Development begins fifth or sixth week of development.
The inferior glands form above the superior glands but descend below them.
The glands are made up of four types of cell:
1. Chief cells - these are the cells which secrete the parathyroid hormone (PTH).
2. Oxyphil cells - these have a secretory function but their precise role is not clear.
3. Adipose tissue - these are fat cells which add bulk to the glands.
4. Fibrovascular stroma - this is fibrous tissue that gives form to the glands containing the capillaries supplying them with blood.
Accidental removal during total thyroidectomy - parathormone deficiency
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