Anatomy of the Thyroid Flashcards
what are the components of the thyroid?
2 lateral lobes (right and left) and an isthmus (narrow connecting band between lobes)
where do the lobes of the thyroid attach?
lateral aspects of the thyroid and cricoid cartilage
what is the isthmus and where is it found?
band connecting 2 lobes of thyroid
sits in front of 2nd and 3rd cartilages of trachea
how would an enlarged or lump in the thyroid move during swallowing and why?
will move superiorly then inferiorly with the larynx during swallowing
due to close relationship with larynx and trachea
what is a goitre?
enlarged gland
where are the 4 parathyroid glands located?
posterior surfaces of lateral lobes of thyroid
what is the pyramidal lobe?
a third lobe of the thyroid which is present in some people
originates from one lobe (usually left) and attaches superiorly to the thyroid cartilage but can extend up to hyoid bone in some
where does the thyroid gland originate?
midline epithelial proliferation at the junction between the anterior 2/3rds and posterior 1/3rd of the tongue (foramen caecum)
where does the thyroid move to during development?
migrates inferiorly form the foramen caecum to the area of the larynx/trachea while remaining attached to the tongue via the thyroglossal duct
when does the thyroid reach its final position?
week 7 of deveopment
what forms compartments in the neck?
invaginations of deep fascia
what is the platysma and what nerve innervates it?
thin muscle in superficial fascia of the neck which controls facial expression and supplied by facial nerve (cringe muscle)
what are the fascial compartments of the neck?
prevertebral (deep) fascia
investing fascia
2 carotid sheaths
pretracheal fascia
what is contained within the prevertebral fascia?
posterior compartment
postural neck muscles
cervical vertebrae
what is contained within the investing fascia?
encloses all the other neck fascial compartment and 2 pairs of muscles
- trapezius
- sternocleidomastoid
what is contained within the carotid sheaths?
located anterolaterally vagus nerves deep cervical lymph nodes carotid arteries internal jugular vein
what is contained within the pretracheal fascia?
anterior and central oesophagus trachea thyroid gland strap muscles recurrent laryngeal nerves
what are the 2 main muscles in the neck and where do they attach?
trapezius - attaches to spine of scapula and lateral end of clavicle
sternocleidomastoid - sternal head attachment = manubrium of sternum, clavicular head attachment = medial end of clavicle
- both pass superiorly to attach to the mastoid process of temporal bone
where are the carotid sheaths?
deep to investing fascia and located anterolaterally in the neck either side of thyroid
where do the carotid sheaths attach?
superiorly = base of skull around jugular foramen and entrance to carotid canal
what is the function of the carotid sheaths?
blend with mediastinal fascia
enclose internal jugular vein, common and internal carotids, vagus nerve and deep cervical lymph nodes
blood supply to the thyroid?
inferior thyroid artery (branch off subclavian)
superior thyroid (branch off external carotid)
thyroid ima sometimes present (can come off brachiocephalic trunk or common carotid)
venous drainage of thyroid?
superior thyroid and middle thyroid veins (drain into internal jugular veins) inferior thyroid (drain into brachiocephalic viens) then into IVC etc
lymphatic drainage of thyroid?
deep cervical lymph nodes (superior and inferior)
pretracheal and paratracheal nodes (on trachea)
right = deep cervical nodes drain into right lymphatic duct and then to right venous angle
left = deep cervical nodes drain into thoracic duct then into left venous angle
describe course of the vagus in the neck
branch from medulla oblongata
exits skull via jugular foramen
descends through carotid sheath
course of vagus in thorax?
descends through chest
- right = lateral to trachea
- left = left side of aortic arch
both travel posterior to lung hilum and attached to the oesopahgus
right/left recurrent laryngeal nerves?
right = loops around right subclavian left = loops around arch of aorta
connection between right subclavian and arch of aorta?
same embryological origin - 4th aortic arch artery
what are strap muscles?
thin long muscles in the neck
what are the superficial strap msucles?
sternohyoid
omohyoid
what are the deep strap muscles?
thyrohyoid
sternothyroid
surgical approaches to thyroid gland?
thyroidectomy
endoscopy assisted thyroidectomy
endoscopic trans-axillary approach
endoscopic trans-breast approach
regions of the neck
anterior triangle - between mandible, jugular notch and SCM
posterior triangle - between trapezius, clavicle and SCM
what separates the anterior and posterior triangle of the neck?
sternocleidomastoid
what are langers lines?
lines of tension/cleavage lines
where is a classical thyroidectomy incision made?
collar incision made through skin and platysma within langer line
incision just superior to clavicles and jugular notch
what can injury to the recurrent nerve cause?
paralysis of the vocal cord
unilateral injury = hoarseness/weak voice, cough
bilateral = aphonia, inability to close rima glottidis to prevent aspiration or to produce a cough
what nerve innervates the trapezius and sternocleidomastoid?
spinal accessory nerve (CN 11)
venous drainage in the neck?
external jugular vein runs within superficial fascia and drains into subclavian
anterior jugular vein runs in superficial fascia and drains into external jugular
course of vagus in the abdomen?
both vagus nerves pass through the diaphragm with the oesophagus then divide into terminal branches on surface of stomach
supply abdominal organs with parasympathetic axons to the distal midgut
where do the inferior thyroid veins lie?
on the anterior surface of the trachea and thyroid
what is ectopic thyroid tissue?
thyroid tissue outside the gland
can be located anywhere in the migratory path
what does the right recurrent laryngeal nerve do?
provides somatic motor supply to most of the skeletal muscles that move the right vocal cord (same with left)
