Isthmus of Thyroid Gland
The structure indicated is the isthmus of the thyroid gland
The thyroid gland sits anteriorly in the neck, just inferior to the thyroid cartilage
. It is located deep to the overlying strap muscles
(sternohyoid, sternothyroid and omohyoid). It has two lateral lobes
connected in the centre by the isthmus
The isthmus lies over the 2nd
rings of the trachea
The lateral lobes extend from the lateral aspects of the thyroid cartilage down as far the 6th
ring of the trachea.
Occasionally a pyramidal lobe
is present, which is an upward extension of the isthmus, and is a remnant of the embryological development of the thyroid gland from its descent from the floor of the pharynx.
The thyroid gland is supplied by three arteries
- Superior thyroid artery
- Inferior thyroid artery
- Thyroid ima artery
The thyroid gland is drained by three veins
- Superior thyroid vein
- Middle thyroid vein
- Inferior thyroid veins
The parathyroid glands
sit on the deep surface of the lateral lobes. There are usually four, with a superior and inferior parathyroid gland lying on either side.