The parathyroid glands are 4 small glands embedded in the thyroid gland that contain spherical cells. They secrete parathyroid hormone which regulates blood calcium levels by increasing calcium levels when they are low, as calcium is important for muscle contraction, blood clotting, and nerve impulse transmission.

1. Parathyroid

2.  4 small glands embedded in the posterior surface of
each thyroid gland lobe.
 Surrounded by connective tissues capsules.
 Cell are spherical.

3.  Parathyroid hormone (PTH)
 Secretion is regulated by blood calcium level.
 Main function PTH – increases when blood calcium is
important for:
(a)Muscle contraction
(b)Blood clotting
(c)Nerve impulse transmission