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Specimen Image

Image removed.Structure[edit]

Features[edit]

Image removed.

 

The thyroid gland surrounds the cricoid and tracheal cartilages and consists of two lobes. This image shows a variant thyroid with a pyramidal lobe emerging from the middle of the thyroid.

The thyroid gland is a butterfly-shaped organ composed of two lobes, left and right, connected by a narrow tissue band, called an "isthmus".[4] It weighs 25 grams in adults, with each lobe being about 5 cm long, 3 cm wide, and 2 cm thick and the isthmus about 1.25 cm in height and width.[4] The gland is usually larger in women than in men, and increases in size during pregnancy.[4][5]

The thyroid is near the front of the neck, lying against and around the front of the larynx and trachea.[4] The thyroid cartilage and cricoid cartilage lie just above the gland, below the Adam's apple. The isthmus extends from the second to third rings of the trachea, with the uppermost part of the lobes extending to the thyroid cartilage and the lowermost around the fourth to sixth tracheal rings.[6] The infrahyoid muscles lie in front of the gland and the sternocleidomastoid muscle to the side.[7] Behind the outer wings of the thyroid lie the two carotid arteries. The trachea, larynx, lower pharynx and esophagus all lie behind the thyroid.[5] In this region, the recurrent laryngeal nerve[8] and the inferior thyroid artery pass next to or in the ligament.[9] Typically, four parathyroid glands, two on each side, lie on each side between the two layers of the thyroid capsule, at the back of the thyroid lobes.[4]

The thyroid gland is covered by a thin fibrous capsule,[4] which has an inner and an outer layer. The inner layer extrudes into the gland and forms the septa that divide the thyroid tissue into microscopic lobules.[4] The outer layer is continuous with the pretracheal fascia, attaching the gland to the cricoid and thyroid cartilages[5] via a thickening of the fascia to form the posterior suspensory ligament of thyroid gland, also known as Berry's ligament.[5] This causes the thyroid to move up and down with the movement of these cartilages when swallowing occurs.[5]

Specimen Number
17