Neck Region

Question 1

Thyroid Gland— location, extent, parts.

Answer 1

It’s an endocrine gland, located in the front and sides of the lower part of neck, opposite the C5 -C7 and T1 vertebral levels. It embraces the upper part of trachea.
Each lobe extends from the middle of the thyroid cartilage to the 5th Tracheal ring, while isthmus extends from the 2nd-4th tracheal rings.

Parts
2 lateral lobes and an isthmus which joins the two lobes across the midline.
Each lobe has
-An apex
-A base
-3 surfaces: Medial, lateral , posterolateral
-2 borders: Anterior and Posterior

Isthmus has

• 2 surfaces : Anterior and posterior
• 2 borders : Superior and Inferior

Question 2

Blood supply of Thyroid gland?

Answer 2

Arterial Supply
1. Superior Thyroid artery (branch of Ext carotid).-Supplies upper 2/3rd of lobe and upper half of isthmus.
Divides into ant and post branches near apex. Anterior branch anastomoses with its fellow from opp. side at the upper border of isthmus.
Posterior branch descends along posterior border and anastomoses with Ascending branch of inf thyroid artery.

2. Inferior thyroid artery (branch of Thyrocervical truck which arises from Subclavian artery)— supplies lower 1/3rd of lobe and lower half of isthmus.
3. Lowest thyroid artery (branch of Brachiocephalic trunk)
4. Accessory thyroid branches of esophageal and tracheal arteries

Venous drainage:

1. Superior thyroid veins - drain into IJV (internal jugular vein)
2. Middle thyroid veins - drain into IJV
3. Inferior thyroid veins- drain into Left brachiocephalic vein
4. Fourth vein of Kocher- emerges between middle and inferior veins and drains into IJV

Question 3

Why do thyroid swellings move with degluttition?

Answer 3

The false capsule of thyroid gland is derived from the pretracheal layer of deep cervical fascia which splits to enclose the gland and gets attached to the oblique line of thyroid cartilage and to the arch of cricoid cartilage.

A fibrous band called ligament of Berry derived from this fascia connects the capsule of the lateral lobe to the cricoid cartilage.

When traced above, the pretracheal fascia is attached to the hyoid bone.

Thus capsule of thyroid gland is attached to laryngeal cartilage and also hyoid bone, which moves up and down during swallowing.
Therefore, the thyroid gland moves up and down during swallowing.

This helps to clinically distinguish between thyroid swelling and other swellings of neck.