Thyroid and Parathyroid Anatomy Flashcards
What vertebral level is the thyroid positioned?
Between C5 and T1 vertebrae
What is the structure of the gland itself
Butterfly shaped gland
R and L lobe joined by a central isthmus
Surrounded by fibrous connective tissue capsule that sends septa deep within gland that supports glandular tissue
wraps around the trachea
What is the histology of the thyroid tissue
Simple cuboidal glandular epithelial cells forming lobules with a central colloid
have tight occluding junctions between cells
presence of surrounding parafollicular C cells produce calcitonin small role in managing hypercalcemia
What are the anterior and anterolateral relations of the thyroid gland?
most superficial R & L sternohyoid muscles
superior belly of the R & L omohyoid
R & L thyrohyoid muscles
R & L sternothyroid muscles
Where is the isthmus
Why can you only palpate the isthmus?
Located between the second and third tracheal rings C6 and C7
What are the other relations of the thyroid gland?
Sits anterior to the trachea and oesophagus
Laterally is the carotid sheath
Left and right recurrent laryngeal nerves that ascend to larynx trachea and oesophagus superiorly to the posteromedial aspect of the thyroid gland
What is the arterial supply of the thyroid
Left and right Inferior thyroid arteries
Stem from the left and right thyrocervical trunks arising from the subclavian arteries
supply the posterioinferior aspect of the gland
Left and right superior thyroid arteries that stem from the external carotid artery and
What is the venous drainage?
Superior thyroid veins (R&L) drain superior pole
Middle thyroid veins (R&L) drain middle of lobes
Both drain into the internal jugular vein
Inferior thyroid veins (R&L) drain into the brachiocephalic veins
What is significant about surrounding nervous innervation to the larynx?
R and L vagus nerve passes down in the carotid sheath and then sends out a branch
Right recurrent laryngeal nerve passes under the right subclavian artery and travels superiorly in close association with the inferior thyroid artery to the posteromedial aspect of the thyroid
Left recurrently laryngeal loops under the arch of the aorta and rises superiorly exactly like the right recurrent laryngeal
What is the embryology of the thyroid gland?
Form early in development lots of development dependant on thyroid hormones
Starts as thyroid primordium in a region known as the foramen caecum on the pharyngeal floor
Descends through the thyroglossal duct inferiorly to its position inferior to the larynx
the thyroglossal duct usually obliterates completely. Cells can be left in the duct which form painless cysts
What fasical envelope is the thryoid located in and with what other strucutures?
The pretracheal fascia
with the trachea and oesophagus
What is a thyroidectomy and then what is a near total thyroidectomy?
Thyroidectomy is removal of the whole thyroid gland i
Near total thyroidectomy is slightly more preservative and is done to protect the left and right recurrent laryngeal nerves as well as the parathyroid glands
What is the thyroid ima artery
Present in 10% of people small unpaired thyroid artery that rises from the brachiocephalic trunk
must be considered when performing procedures in the midline of the neck as is a potential source of bleeding
Why might someone have stridor or a hoarse voice after thyroid surgery
There has been damage to the left of right recurrent laryngeal nerves
Why might someone have tetany following a thryroidectomy
There was removal of the parathyroid glands meaning there is no PTH produced therefore the person has hypocalcemia
