Parathyroid glands

The Parathyroid Glands
The parathyroid glands (Fig. 1177) are small brownish-red bodies, situated as a rule between the posterior borders of the lateral lobes of the thyroid gland and its capsule.

parathyroid glands
[Gk. para, beside, akin to + thyra, a door]
Four endocrine glands, embedded in the surface of the thyroid gland, that secrete parathyroid hormone and raise blood calcium levels.
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The Parathyroid Glands
The parathyroid glands are 4 tiny structures embedded in the rear surface of the thyroid gland. They secrete parathyroid hormone (PTH) a polypeptide of 84 amino acids.

The endoderm forms tissues and organs associated with the digestive and respiratory systems. Many endocrine structures, such as the thyroid and parathyroid glands, are formed by the endoderm. The liver, pancreas, and gall bladder arise from endoderm.

In vertebrates, this innermost layer of cells goes on to form the linings of the gut (esophagus, stomach, intestines, rectum, colon), pharyngeal pouch derivatives (tonsils,thyroid, thymus, parathyroid glands), lungs, liver, gall bladder, pancreas.

In humans, first pair of pouches becomes a cavity of middle ear and auditory tube; second pair becomes tonsils, while third and fourth pairs become thymus and parathyroid glands. This makes sense only if fish are ancestral to other vertebrate groups.

See also: Class, Bone, Human, Embryo, Organ