Session 11: Self-Study Flashcards
How do we test the function of the thyroid gland?
Thyroid function tests TSH, T3 and T4 levels
What is the first-line imaging choice when investigating thyroid pathology like thyroid goitre or lump?
Ultrasound
Where are the parathyroid glands in relation to the thyroid gland? How many are there, and what is their function?
Two paired endocrine glands positioned behind left and right lobes of the thyroid gland. Usually 4 in total. It is found within the fascia surrounding the thyroid gland but are separate. Produce PTH and calcitonin that is key in the regulation of calcium levels.
What is a pyramidal lobe?
A third thyroid lobe due to persistent remnant of the thyroglossal duct which develops into thyroid gland tissue. This is failure of fusion of the distal part of the thyroglossal duct.
Why does the thyroid gland move up on swallowing?
Ensheathed in the pretracheal fascia which attaches to the hyoid bone. The hyoid bone elevates on swallowing and so will the thyroid gland. The posterior surface of the thyroid gland is also attached to the cricoid cartilage and trachea by a suspensory ligament. When the larynx elevates on swallowing so will the thyroid gland. Neck lumps that move with swallowing can be localised to the thyroid gland.
What collection of muscles lie anteriorly the thyroid gland?
Infrahyoid muscles. They act to stabilise the larynx during its movement during swallowing alongside the suprahyoids.
What is a thyroid ima and where might it be found? Why might this cause difficulties for surgical access to the airway?
An artery present in a very small proportion of people. If it is present it can arise from the brachiocephalic trunk or arch of aorta. It will ascend in front of the trachea to the isthmus. It presence may prove problematic if accessing the trachea for a surgical airway or during thyroidectomy. It can be a source of rapid bleeding if damaged and when cut can retract behind the mediastinum so difficult to reach and ligate.
Which veins drain the thyroid gland and to which main vessels do they subsequently drain?
Superior and middle thyroid veins drain to IJV. Inferior thyroid vein drain to the left brachiocephalic vein.
From which main arteries do each of the vessels arise (sup and inf thyroid arteries)?
Sup - first branch of the external carotid artery Inf - thyrocervical trunk from subclavian
What are the nerves lying in close proximity to these arteries? What would be a consequence of their injury?
External branch of the sup laryngeal nerve supplying motor to the cricothyroid muscle is in close proximity to the superior thyroid artery. The inferior thyroid artery is in close proximity to the recurrent laryngeal nerve which supplies the motor to all the muscles of the larynx except cricothyroid muscle.
A 25 year old woman visited her GP because of a swelling just beneath her hyoid bone. She informed the doctor that although the swelling was painless, she was worried because it seemed to be getting larger. The doctor referred her to the hospital where further examination revealed that the swelling was a fluid-filled soft tissue mass that moved up when the patient swallowed and stuck her tongue out. No other neck masses or lymphadenopathy were present. Lab tests showed absence of radioactive iodine in the swelling. What is the most probable cause of the swelling? Explain your answer, particularly in relation to the clinical findings.
Thyroglossal duct cyst. The lump is fluid-filled and move up on both swallowing AND tongue protrusion. It is painless and also no radioactive iodine reaching it meaning it is discontinuous with the actual thyroid gland.
Why might you be concerned about lymphadenopathy in the neck, particularly in the context of a neck swelling?
Most often due to an infectious causes or secondary to malignancy spreading. Deep cervical lymph nodes receive drainage directly from head and neck structures deep in the neck so a neck lump could be the first sign of pathology of an underlying HNC.
What cervical nerve roots contribute to the cervical plexus?
Anterior rami of C1-C4
What is the ansa cervicalis; what roots of the plexus contribute to this and is it motor/sensory or mixed?
Loop of nerves formed by C1-C3 nerve roots. Entirely muscular and gives off supply to the infrahyoid muscles.
What anatomical structure does the ansa cervicalis overlie anteriorly?
Anterior on or in the carotid sheath