Surgical anatomy of the thyroid gland. Flashcards
Where does the sternocleidomastoid muscel attache?
base of the head to the clavicle
Where does the thyroid gland lie?
It lies in the anterior triangle
more specifically in the muscular triangle below the hyoid bone and medial to the omohyoid muscle
The investing fascia splits aroud what muscles?
it splits and fully surrounds almost every muscle in the outter neck
the prevertebral layer of fascia is over what muscles?
it overlies the deep muscles of the neck
the carotid sheet overlies which structures?
it overlies the common carotid, vagus nerves, and internal jugular veins
What structures does the pretracheal layer of faschia surround?
the thyroid, the trachea and esophagus, and the internal jugular vein
how many infrahyoid muscles are there?
there are 4 infrahyoid muscles -
- omohyoid muscle
- sternohyoid muscle (sternum to hyoid)
- thyrohyoid muscle (deep)
- Sternothyroid muscle (deep)
*these are often refered to as the ‘strap muscles’
what nerve supplies the hyroid muscles?
the Ansa Cervicalis (C1,2,3) spinal cord levels -
the loop of the ansa cervicalis lies wehre?
overlies the carotid muscles in the fascia
Which muscle gets it’s innervation dirrectly from the C1 (not through the ansa)
The thyrohyoid muscle - supplied by C1 fibers not through the ansa
The ansa supplies the muscle from top to bottom? Or from bottom up?
from bottom up the uscle - so if you have to cut the muscle, it’s best to cut more superiorly
What is the thyroid gland?
It is a ductless gland (distributes through the blood) endocrine - that is butterfly shapped with two lobes on the opposite sides with a midline in between
Where does the thyroid gland sit?
two lateral lobes - oblique line of thyroid cartilage - 2X1X1
what percent of people have a pyramidal lobe?
21% - have a bit of thyroid tissue that spreads superior to the isthmus of the thymus gland -
Where does the thymus gland start embryologically?
from the foramen cecum - then it descends infront of the hyoid bone, then down further into the bottom of the neck - travels a few inches from its original placement on the tongue
if someone has a pyramindal lobe of the thyroid gland, what might you see when the patient sticks their tongue out?
You could potentially see a little cyst that moves when the patient moves their tongue - medially along the edge of the embryological development
the thyroidf gland is covered in what fascia?
covered in pretracheal fascia - so it moves with swallowing - also, if it moves with the tongue, then there could be a remnant on the tongue
What lies laterally to the thyroid gland?
carotid fascia - so the thyroid gland is limited both laterally and superiorly - which is why large goitres often enlarge inferiorly - could extend retrosternally and squeeze the trachea - or it could constrict the trachea/weaken the trachea
What is the blood supply to the thyroid gland?
3 arteries
- superior thyroid (from external Carotid)
- inferior thyroid( from SubClavian - 1stpart)
- 10% of people have the thyroid ima artery ( mosly comes form the arch of aorta or braciocephalic) - normally runs to the isthmus
3 veins
- superior (internal jugular)
- middl e( internal jugula)
- Inferior (left brachiocephalic)
What are the nearby nerves of the thyroid gland?
extranal laryngeal nerve runs really close to the superior thyroid artery *this means you want to tie the artery off as close as possible to the thyroid gland to prevent damage to these nerves
- recurrent laryngeal nerve (supplies every single muscle in the larynx- so if they’re damaged you have a rough time breathing) runs close to the inferior thyroid artery
With the laryngeal nerve and the infrathyroid artery - where do we tie off the artery?
we tie them off further away from the thyroid b/c they converge closer to the thyroid gland (exact opposite from the strucutres on the opposite side )
What are the posteromedial relations of the thyroid gland?
2 cartilages = thyroid and cricoid
2 muscles = cricothyroid and inferior constrictor
2 tubes - trachea and oesophagus
2 nerves = recurrent laryngeal and external laryngeal
where do the parathyroid glands sit?
they sit behind the parathyroid and they sit in fat - they are invovled in calcium metabolism and if you have a tumour here you could have hypercalcaemia (bone issues, kidney stones, etc) -
*really hard to differentiate what is fat and what is parathyroid*
why do we place ‘removable’ stitches in a thyroid gland surgery?
because post op bleeidng could compress the trachea - so you wnat to be able to remove it quickly to reduce pressure
What should you monitor after a thyroid gland surgery?
calcium level - to ensure no damage to the parathyroid glands behind the thyroid glands.
