Thyroid gland Flashcards
Arterial supply
The thyroid gland secretes hormones directly into the blood. Therefore it needs to be highly vascularised. Blood supply to the thyroid gland is achieved by two main arteries; the superior and inferior thyroid arteries. These are paired arteries arising on both the left and right.
The superior thyroid artery is the first branch of the external carotid artery. After arising, the artery descends toward the thyroid gland. As a generalisation, it supplies the superior and anterior portions of the gland.
The inferior thyroid artery arises from the thyrocervical trunk (which in turn is a branch of the subclavian artery). The artery travels superomedially to reach the inferior pole of the thyroid. It tends to supply the postero-inferior aspect.
In a small proportion of people (around 10%), there is an additional artery present; the thyroid ima artery. It comes from the brachiocephalic trunk of the arch of aorta, supplying the anterior surface and isthmus.
veinous drainage of the thyoid gland
Venous drainage is carried out by the superior, middle and inferior thyroid veins, which form a venous plexus. The superior and middle veins drain into the internal jugular veins, whereas the inferior drains into the brachiocephalic vein.
nerve innervation throid gland
The thyroid gland is innervated by branches derived from the sympathetic trunk. However, these nerves do not control endocrine secretion – release of hormones is regulated by pituitary gland.
desribe anatomical location of the thyroid gland
The thyroid gland is located in the anterior neck, spanning between the C5 and T1 vertebrae. It is an endocrine gland, divided into two lobes which are connected by an isthmus. It is said to have a butterfly shape.
It lies behind the sternohyoid and sternothyroid muscles, wrapping around the cricoid cartilage and superior tracheal rings. It is inferior to the thyroid cartilage of the larynx. The gland is in the visceral compartment of the neck, along with the trachea, oesophagus and pharynx. The compartment is bound by pretracheal fascia.
During development, the thyroid gland initially forms in the floor of the primitive pharynx, near the base of the tongue. It descends down the neck to lie in its adult anatomical position.
what type of gland is the thyroid
ENDOCRINE
