Session 11: Anatomy of the Thyroid Gland & Head and Neck Cancers Flashcards
Vertebral location of the thyroid gland.
C5 to T1
Explain the anatomical position of the thyroid in relation to other structures.
Lies posterior to the sternohyoid and sternohyoid muscles.
It wraps around the cricoid cartilage and superior tracheal rings.
Found inferior to the thyroid cartilage and the gland is in the visceral compartment of the neck along with the trache, oesophagus and the pharynx.
The compartment is bound by pretracheal fascia.
During development where does the thyroid gland initially form?
Near the base of the tongue in the primitive pharynx.
It then descends down the neck to lie in its adult anatomical position.
As the thyroid gland descends during development, what does it move through?
The thyroglossal duct.
What happens to the thyroglossal duct?
It will normally fuse and regress.
What happens in case the duct doesn’t fuse correctly?
It may happen in around 50% individuals that the distal portion of the duct contines as a pyramidal lobe.
This becomes an extra piece of thyroid tissue but has no clinical consequence.
What are thyroglossal cysts?
If other portions of the duct persist that is not the distal portion.
How do thyroglossal cysts present?
As a mass in the midline of the neck.
Can be excised surgically.
Anterolateral structures to the thyroid gland.
Sternothyroid
Superior belly of omohyoid
Sternohyoid
Posterolateral structures to the thyroid gland.
Carotid sheath with common carotid, internal jugular vein and the vagus nerve.
Posteromedial structures to the thyroid gland.
Larynx
Trachea
Pharynx
Oesophagus
External laryngeal nerve
Recurrent laryngeal nerve
Blood supply of the thyroid gland.
Superior and inferior thyroid arteries.
From what and where does the superior thyroid artery arise?
First branch of the external carotid artery.
After it arises it descends toward the thyroid gland.
What does the superior thyroid artery supply?
Superior and anterior portions of the thyroid gland.
What does the inferior thyroid artery arise from?
The thyrocervical trunk which is a branch of the subclavian artery.
Then travels superomedially to reach the inferior pole of the thyroid.
What does the inferior thyroid artery supply?
The posteroinferior aspect of the gland.
What is the thyroid ima artery?
In 10% of people there is an extra artery called the thyroid ima artery.
Comes from the brachiocephalic trunk of the arch of the aorta.
Venous drainage of the thyroid.
Superior, middle and inferior thyroid veins which form a venous plexus.
What does the inferior, middle and superior thyroid veins draini into?
Superior and middle -> internal jugular veins
Inferior -> brachiocephalic vein
Innervation of the thyroid gland.
Branches derived from the sympathetic trunk.
These nerves do not control the endocrine secretion as they are controlled by the pituitary gland.
Common sites for cancer in head and neck.
Lip/oral cavity
Pharynx
Larynx
Thyroid
What is most common type of cancer in head and neck?
Squamous cell carcinoma (90%)
Risk factors of head and neck cancers.
Alcohol
Tobacco (including chewing tobacco)
Age (older patients)
Male
Betel nut chewing
Dental hygiene
Long term exposeure to sunglight or sunbeds
