thyroid anatomy Flashcards
where is the thyroid located
5th cervical to 1st thoracic vertebrae
2-4th tracheal rings
how big is the thyroid in adults
12-15mm
25-30g
when would the thyroid increase in size
pregnancy
menstruation
what is the parasympathetic nerve supply
vagus nerve
what is the sympathetic nerve supply
superior, middle, and inferior ganglia of sympathetic trunk
what is the arterial blood supply of the thyroid
superior and inferior thyroid arteries
where do the superior and inferior thyroid arteries originate
superior = branch of external carotid inferior = subclavian
what is the venous blood supply of the thyroid
superior, middle, and inferior thyroid veins
where do the superior, middle, and inferior thyroid veins originate
superior & middle = internal jugular
inferior = brachiocephalic veins
how is the thyroid gland attached
posterior suspensory ligament (aka berry ligament)
what does the thyroid consist of
2 lateral lobes (L & R) and an isthmus
what is the isthmus
narrow connecting band within the thyroid
where do the lobes attach
cricoid cartilages and to the trachea
where is the isthmus located
the 2nd & 3rd cartilages of the trachea
a lump within the gland will do what on swallowing
move superiorly then inferiorly with the larynx
how many parathyroid glands are there
4
where are the parathyroid glands located
the posterior surfaces of the thyroid gland’s lateral lobes
what is a pyramidal lobe
anatomical variant
where does a pyramidal lobe commonly originate from
left lateral lobe, may extend as far superiorly as the hyoid bone
where do most pyramidal lobes attach
superiorly to thyroid cartilage
where does the thyroid gland begin its development
as a midline epithelial proliferation at the junction between the anterior 2/3rds and the posterior 1/3rd of the tongue (aka foramen caecum in the adult)
how does the thyroid migrate during development
migrates inferiorly whilst remaining attached to the tongue via the thyroglossal duct
when does the thyroid reach its final position during development
7th week of development
where can Thyroglossal duct cysts or ectopic thyroid tissue be found
any position in the thyroid migratory path
what is a platysma
A skeletal muscle in the superficial fascia, extending from the collar bone to the angle of the jaw.
whats the innervation of the platysma muscles
CN VII (fascial nerve)
what group of muscles does the platysma muscles belong to
muscles of facial expression
how many fascial compartments are located within the neck
4
what are the 4 neck fascial compartments
prevertebral (deep) fascia
investing fascia
carotid sheaths x2
pretracheal fascia
where is the prevertebral (deep) fascia located
posteriorly within the neck (behind vertebra)
what is located within the prevertebral (deep) fascia
postural neck muscles
cervical vertebrae
what is the investing fascia
encloses ALL neck fascia
what muscles are located within the investing fascia
trapezius
sternocleidomastoid
where is the carotid sheaths located
anterolaterally (either side of the thyroid)
what is located within each carotid sheaths
vagus nerve
deep cervical lymph nodes
carotid arteries (common then internal)
internal jugular vein
where is pretracheal fascia located
anteriorly (around the thyroid)
what is located within pretracheal fascia
oesophagus trachea thyroid strap muscles recurrent laryngeal nerves
what are the carotid sheaths
bilateral “tubes”of deep fascia
where do the carotid sheaths attach (superiorly and anteriorly)
superiorly = base of the skull (around the jugular foramen & the entrance to carotid canal)
inferiorly = blend with the mediastinal fascia
what is the thyroid IMA artery
anatomical variant which lies centrally and supplies thyroid with material blood
what is the lymphatic drainage of the thyroid
superior & inferior deep cervical lymph nodes
tracheal lymph nodes
what are the tracheal lymph nodes that supply the thyroid
Pretracheal node
Paratracheal nodes
where does the RIGHT lymph nodes of the thyroid originate
Right lymphatic duct
to the
Right venous angle
where does the LEFT lymph nodes of the thyroid originate
Thoracic duct
to the
Left venous angle
how many strap muscles are there
4
name the 4 strap muscles
thyrohyoid
omohyoid
sternohyoid
sternothyroid
what are the 4 surgical approaches to the thyroid gland
Classical thyroidectomy = open surgery
Endoscopically assisted thyroidectomy
Endoscopic trans-axillary approach
Endoscopic trans-breast approach
describe a classical thyroidectomy incision
a “collar” incision just superior to the clavicles and jugular notch is made in a natural crease though skin and platysma
what nerve may be damaged during thyroid surgery
recurrent laryngeal
what does damage to the recurrent laryngeal result in
paralysis of vocal cords
what symptoms would you expect from recurrent laryngeal damage (unilateral and bilateral)
unilateral = “hoarseness” or weakness of the voice and a weak cough
bilateral = aphonia and inability to close the rima glottidis resulting in an inability to to prevent aspiration or to produce a good cough
what is aphonia
inability to produce sound
