Surgical anatomy of the thyroid gland.

Question 1

Where does the sternocleidomastoid muscel attache?

Answer 1

base of the head to the clavicle

Question 2

Where does the thyroid gland lie?

Answer 2

It lies in the anterior triangle

more specifically in the muscular triangle below the hyoid bone and medial to the omohyoid muscle

Question 3

The investing fascia splits aroud what muscles?

Answer 3

it splits and fully surrounds almost every muscle in the outter neck

Question 4

the prevertebral layer of fascia is over what muscles?

Answer 4

it overlies the deep muscles of the neck

Question 5

the carotid sheet overlies which structures?

Answer 5

it overlies the common carotid, vagus nerves, and internal jugular veins

Question 6

What structures does the pretracheal layer of faschia surround?

Answer 6

the thyroid, the trachea and esophagus, and the internal jugular vein

Question 7

how many infrahyoid muscles are there?

Answer 7

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’

Question 8

what nerve supplies the hyroid muscles?

Answer 8

the Ansa Cervicalis (C1,2,3) spinal cord levels -

Question 9

the loop of the ansa cervicalis lies wehre?

Answer 9

overlies the carotid muscles in the fascia

Question 10

Which muscle gets it’s innervation dirrectly from the C1 (not through the ansa)

Answer 10

The thyrohyoid muscle - supplied by C1 fibers not through the ansa

Question 11

The ansa supplies the muscle from top to bottom? Or from bottom up?

Answer 11

from bottom up the uscle - so if you have to cut the muscle, it’s best to cut more superiorly

Question 12

What is the thyroid gland?

Answer 12

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

Question 13

Where does the thyroid gland sit?

Answer 13

two lateral lobes - oblique line of thyroid cartilage - 2X1X1

Question 14

what percent of people have a pyramidal lobe?

Answer 14

21% - have a bit of thyroid tissue that spreads superior to the isthmus of the thymus gland -

Question 15

Where does the thymus gland start embryologically?

Answer 15

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

Question 16

if someone has a pyramindal lobe of the thyroid gland, what might you see when the patient sticks their tongue out?

Answer 16

You could potentially see a little cyst that moves when the patient moves their tongue - medially along the edge of the embryological development

Question 17

the thyroidf gland is covered in what fascia?

Answer 17

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

Question 18

What lies laterally to the thyroid gland?

Answer 18

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

Question 19

What is the blood supply to the thyroid gland?

Answer 19

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)

Question 20

What are the nearby nerves of the thyroid gland?

Answer 20

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

Question 21

With the laryngeal nerve and the infrathyroid artery - where do we tie off the artery?

Answer 21

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 )

Question 22

What are the posteromedial relations of the thyroid gland?

Answer 22

2 cartilages = thyroid and cricoid

2 muscles = cricothyroid and inferior constrictor

2 tubes - trachea and oesophagus

2 nerves = recurrent laryngeal and external laryngeal

Question 23

where do the parathyroid glands sit?

Answer 23

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*

Question 24

why do we place ‘removable’ stitches in a thyroid gland surgery?

Answer 24

because post op bleeidng could compress the trachea - so you wnat to be able to remove it quickly to reduce pressure

Question 25

What should you monitor after a thyroid gland surgery?

Answer 25

calcium level - to ensure no damage to the parathyroid glands behind the thyroid glands.