The Thyroid Gland is a butterfly-shaped gland found in the lower front part of the neck. Its lobes (the butterfly wings) wrap around the trachea and are connected at the centre by an Isthmus. The thyroid gland’s primary function is to secrete hormones that regulate our metabolic rate, protein synthesis and growth. These notes will outline the Anatomy of the Thyroid Gland for nursing and health care students.
Anatomy of the Thyroid Gland Part 1: Structure
As we mentioned above, the thyroid gland is nicknamed the butterfly-shaped organ, and this is because it has two lobes on either side and a narrow tissue in the midline known as the Isthmus. Each lobe spans up to 5cm long and 3cm wide, with the average weight ranging from 25-30g, making it the largest endocrine gland in our body. The thyroid gland is typically larger in women, and its size increases during pregnancy.
Location wise, the thyroid is found anterior to the trachea (in front of the trachea), and the lobes span from the thyroid cartilage down to the fourth or sixth tracheal rings. The gland is attached to the cricoid and thyroid cartilages through Berry’s ligament, allowing it to shift position during swallowing.
Anatomy of the Thyroid Gland Part 2: Blood, Lymph and Nerve Supply
Roughly 30mL of blood flows through the thyroid gland every minute, almost five times as much as the blood that flows through the liver. So in comparison, the thyroid gland receives an extensive supply of blood. It has four different blood supplies; the primary blood supply comes from the Superior Thyroid Artery, but it also receives blood from one of the branches of the:
External Carotid Artery
Inferior Thyroid Artery
Once the blood circulates the thyroid gland, it leaves through the Superior and Middle Thyroid Veins, both of which drain into the Internal Jugular Vein.
Regarding lymphatic drainage, the bulk of it passes through the Prelaryngeal Lymph Nodes found over the Isthmus, and the rest goes through the Pretracheal and Paratracheal Lymph Nodes.
Lastly, the thyroid gland receives sympathetic nerves through the superior, middle and inferior cervical ganglion. And it also gets parasympathetic nerves through the superior laryngeal nerve and the recurrent laryngeal nerve.
Now that you’ve understood the Anatomy of the Thyroid Gland, we can hop over to the next topic, the Physiology of the Thyroid Gland.