QS Study

The thyroid is an endocrine gland, situated in the lower part the front and sides of the neck. Grossly, the gland appears brownish-red and the left and right lobes are connected by an isthmus.

Parts

  1. Right lobe.
  2. Left Lobe.
  3. Isthmus.
  4. Pyramidal lobe (Sometime found)

Dimensions

  • Each lobe: 5 cm x 2.5 cm x 2.5 cm.
  • Isthmus: 1.2 cm x 1.2 cm.
  • Weight: 25 gm.

Location: It situated in front and at the sides of trachea opposite 5th, 6th, 7th cervical and 1st thoracic vertebrae in the neck region.

Gross Anatomy

The thyroid gland is situated opposite C5 and T1 vertebra in the anterior neck region. The main purpose of this organ is to produce, store and secrete the iodine-based hormones triiodothyronine (T3) and thyroxine (T4). There is some degree of variability in the mass of the gland, mainly between males and females. The exception to the sex dichotomy of thyroid size is between the ages of eight months to the onset of menarche. The thyroid is the butterfly or “H”-shaped and is composed of two lobes, each with a superior and inferior pole, connected by an isthmus. Each lobe measures approximately 4 cm in length. 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 superficial surface is overlapped by the neck muscles whereas the deep surface is related with the larynx and trachea, pharynx and oesophagus and parathyroid glands.

Gross Anatomy of Thyroid Gland 1

Fig: Gross Anatomy of the Thyroid Gland

Capsules of the thyroid

  1. The true capsule is the peripheral condensation of the connective tissue of the gland.
  2. The false capsule is derived from the pretracheal of the deep cervical fascia.
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