Thyroid Gland Anatomy Flashcards
what are the two sections of the neck?
posterior and anterior triangles
what is the posterior border of the posterior triangle?
trapezius
what is the anterior border of the posterior triangle?
posterior border of the sternocleidomastoid
what is significant about the sternocleidomastoid?
it is the border between the posterior and anterior triangles
how many heads does the sternocleidomastoid have?
2
what are the two heads of the sternocleidomastoid?
clavicular and sternal head
what is significant about the laryngeal prominence of the thyroid cartilage?
gives an idea of where the thyroid is
what spinal nerve supplies the sternocleidomastoid and trapezius?
spinal nerve 11-spinal accessory nerve
where does the trapezius attach inferiorly?
the spine of the scapula and the lateral end of the clavicle
where is the external jugular vein?
superficial fascia superficial to the sternocleidomastoid
what does the external jugular vein drain into?
subclavian vein
where is the anterior jugular vein?
superficial fascia
what does the anterior jugular vein drain into?
external jugular vein
where does the sternal head of the sternocleidomastoid attach?
manubrium of sternum
where does the clavicular head of the sternocleidomastoid attach?
medial end of clavicle
where do both heads of the sternocleidomastoid attach superiorly?
mastic process of the temporal bone
what is important about the facial compartments of the neck?
important for spread of infection
what is the skin important for?
prevents drying out
where is the platysma?
superficial fascia, immediately deep to the skin
what is the platysma?
slender muscle
what group of muscles do the platysma muscles belong to?
muscles of facial expression
what is the platysma innervated by?
cranial nerve 7-facial nerve
what are the 4 fascial compartments called?
innervating, prevertebral (deep), carotid sheaths, pretracheal
what does the investing fascia enclose?
all other neck fascia and the trapezius and sternocleidomastoid
what does the prevertebral (deep) fascial compartment enclose?
postural neck muscles and cervical vertebrae
where is the prevertebral compartment located?
posteriorly
what does the carotid sheath enclose?
common carotid artery, internal jugular vein, deep cervical lymph nodes and vagus nerve
where are the carotid sheaths located?
anterolaterally in the neck, posterolaterally too the thyroid
what does every neuromuscular bundle contain?
lymph nodes
what does the pretracheal fascia enclose?
oesophagus, trachea, thyroid, strap muscles, recurrent laryngeal nerves
what does the thyroid wrap around?
anterior part of trachea
where is the pretracheal fascia located?
anteriorly
where is the retropharyngeal space located?
between pretracheal and prevertebral fascial compartments
what is significant about the retropharyngeal space?
it runs right down to the mediastinum so infection can easily spread
where do the carotid sheaths attach superiorly?
base of skull around the jugular foramen and entrance to carotid canal
what are the four strap muscles called?
sternohyoid, omohyoid, sternothyroid and thyrohyoid
what is the most superficial strap muscle?
sternohyoid
what does omo mean
shoulder
where does the inferior belly of the omohyoid attach?
scapula
what is the fascial sling?
attaches the intermediate tendon of the omohyoid to clavicle
where does the thyroid gland begin development?
a midline epithelial proliferation at junction between anterior 2/3 and posterior 1/3 of tongue
where does the thyroid gland then migrate?
inferiorly whilst remaining attached to tongue via thyroglossal duct
when does the gland reach its final position in relation to the larynx/trachea?
7th week
how many lobes does the thyroid consist of?
2 (left and right)
what connects he two lobes.?
isthmus
where does the isthmus lie anatomically?
anterior to 2nd and 3rd cartilage
wha happens with a goitre during swallowing?
moves superiorly then inferiorly with larynx
how many parathyroid glands are there?
4
where are parathyroid glands located?
posterior surface of thyroid gland, lateral lobes, often embedded in the thyroid
how likely is a pyramidal lobe?
28-55%
what is the pyramidal lobe?
remnant of the thyroglossal duct
often just a band of fibrous tissue, can be ligamentous or can have ectopic thyroid remnants too
where do most pyramidal lobes attach?
superiorly to thyroid cartilage
how many arteries supply the thyroid?
2
what are the arteries supplying the thyroid?
superior and inferior thyroid arteries
where does the superior thyroid artery come from?
1st branch of the external carotid artery
where does the inferior thyroid artery come from?
continuation of thyrocervical trunk which is a branch of the subclavian artery
where does the subclavian artery come from?
brachiocephalic
what else does the brachiocephalic give rise to?
common carotid
where do the inferior thyroid artery supply?
lower lobes
what is a third artery that can supply the thyroid?
variable, thyroidialema
where does the thyroidialema come from?
brachiocephalic trunk o can come right from arch of aorta
how many thyroid veins are there?
three
superior, middle and inferior
where does the superior thyroid vein drain into?
internal jugular vein
where does the inferior vein drain into?
brachiocephalic veins
what is significant about the brachiocephalic veins?
because the left is much longer usually left and right inferior thyroid veins drain into the left brachiocephalic
where is lymph returned via and to on the left side?
thoracic duct to left venous angle
where is lymph returned via and to on the right side?
right lymphatic duct to right venous angle
where does the vagus nerve emerge from?
medulla oblongata
where does the vagus never exit the cranium via?
jugular foramen
where does the vagus never emerge in?
carotid sheaths
what does vagus mean?
vague and wandering
where does the vagus nerve from the oesophageal plexus?
posterior to lung hilum and around oesophagus
where do the vagus nerves pass through the diaphragm?
with oesophagus in oesophagus hiatus
where do the right subclavian artery and arch of aorta both originate from embryonically?
4th aortic arch artery
where does the left vagus nerve link under to become left recurrent laryngeal nerve?
arch of aorta
where does the right vagus nerve link under to become the right recurrent laryngeal nerve?
right subclavian artery
where do the recurrent laryngeal nerves go back to?
larynx
where is the classic thyroidectomy incision?
collar incision made in natural skin creases in direction of Langer lines
superior to clavicles and jugular notch
made through skint to platysma
what can the strap muscles also be called?
infrahyoid muscles (because they are inferior to hyoid bone
where do the recurrent laryngeal nerves ascend in?
groove beween trachea anteriorly and oesophagus posteriorly
on the right in particular it is also very close to the inferior thyroid arteries
what is the risk with ligating inferior thyroid veins?
can damage the recurrently laryngeal nerves
how can the risk of damaging the recurrent laryngeal nerves be avoided?
ligate more laterally
why mobilise the thyroid anteriorly?
to dissect parathyroid glands and their blood supply free from posterior surface of thyroid gland
what does the right recurrent laryngeal nerve do?
provides somatic motor supply to most skeletal muscles that move right vocal cord (intrinsic muscles of larynx)
what can damage of the recurrent laryngeal nerve result in?
paralysis of vocal cord
what does unilateral injury of the recurrent laryngeal nerve cause?
hoarseness or weakness of voice and a weak cough
what does a bilateral injury of the recurrent laryngeal nerve cause?
aphonia (inability to produce sound) and the inability to close the rima glottidis (opening between vocal cords) to prevent aspiration, produce a good cough as this requires closure of the rima glottidis
