left lobe of thyroid gland

The left lobe of the thyroid gland is one of the two lateral lobes that compose the butterfly-shaped thyroid gland, located in the lower anterior neck. The thyroid gland consists of a right lobe and a left lobe, connected by a midline structure called the isthmus. Each lobe lies on either side of the trachea, just below the Adam's apple (thyroid cartilage), extending from approximately the level of C5 superiorly to T1 inferiorly. Each lobe has an average length of approximately 50-60 mm, and the entire gland typically weighs around 25-30 grams.

Anatomical relationships: The left lobe, like the right, is enveloped by the visceral fascia and is covered anteriorly and laterally by the strap muscles (sternothyroid, sternohyoid, and the superior belly of the omohyoid). It is attached to the laryngotracheal complex by the anterior suspensory ligament and the posterior suspensory ligament (ligament of Berry), which connects it to the cricoid cartilage and the first and second tracheal rings.

The blood supply derives from the superior and inferior thyroid arteries.

Asymmetry between lobes: The right lobe is generally larger than the left lobe.