Case 9 anatomy

Question 1

Structure of thyroid gland

Answer 1

Two lobes joined by a central isthmus. Surrounded by a pre-tracheal fissure which connects the thyroid to the trachea

Question 2

How to locate the thyroid gland

Answer 2

Not palpable unless pathology is present i.e. nodules. You can locate it by finding the laryngeal prominence / Adam’s apple then moving inferiorly.

Question 3

What is found within the pre-tracheal fissure

Answer 3

The recurrent laryngeal nerve, oesophagus, trachea and pharynx.

Question 4

Where does the thyroid gland sit

Answer 4

C5 - T1

Question 5

What is posterior to the thyroid gland

Answer 5

The four parathyroid glands which are responsible for calcium homeostasis

Question 6

Thyroid gland embryology

Answer 6

During development the thyroid is located at the base of the tongue at the foramen caecum. It moves down to its normal location through the thyroglossal duct

Question 7

Problems with thyroid gland development

Answer 7

The thyroglossal duct should close. If it doesn’t a thyroglossal cyst can form, this is a differential diagnosis for midline neck lump

Question 8

Blood supply to the thyroid gland

Answer 8

• The superior thyroid artery- a branch of the external carotid artery
• The inferior thyroid artery- a branch of the thyrocervical trunk from the subclavian artery.
Some people have a blood supply via the thyroid ima artery, most commonly a branch of the brachiocephalic trunk

Question 9

Venous drainage of the thyroid gland

Answer 9

Occurs through the superior, middle and inferior thyroid veins. The superior and middle thyroid veins drain into the internal jugular vein. The inferior thyroid vein drains into the brachiocephalic vein.

Question 10

Nervous supply to the thyroid gland

Answer 10

It is innervated by the sympathetic fibres from the superior, middle and inferior cervical ganglia. The recurrent laryngeal nerve (a branch of the vagus nerve) travels behind the thyroid to supply the laryngeal muscle.

Question 11

Lymphatic drainage of the thyroid gland

Answer 11

The lymph node group draining the thyroid includes the Perithyroid, Pre-laryngeal, the Pre-tracheal, Paratracheal, and the Superior and inferior deep cervical.

Question 12

Specialised cells in the thyroid gland

Answer 12

• Follicles- folicular cells surround a lumen
• Colloid is pooled in the follicular lumen and is the site of hormone production and storage
• C cells/parafollicular cells secrete calcitonin for calcium homeostasis
• There are capillaries surrounding the follicles in the extra cellular matrix (ECM)