10 self-study: hyoid muscles + thyroid Flashcards
boundaries of anterior triangle?
anterior: midline
posterior: anterior SCM
superior: inferior mandible
apex: jugular notch of manubrium
roof: subcutaneous tissue of platysma (muscle in superficial cervical fascia)
floor: pharynx, larynx, thyroid
borders of carotid triangle?
superior: posterior belly of digastric
medial: superior belly of omohyoid
lateral: anterior border SCM
how can carotid pulse be felt?
by pressing lightly against the anterior tubercle of the transverse process of C6
where is carotid sinus? innervation? function?
dilation of proximal ICA glossopharyngeal nerve (CN IX) detect changes in arterial BP by baroreceptors (carotid sinus + aortic arch = baroreceptors)
where is the carotid body? innervation? function?
small, oval red mass of TISSUE, sits just ABOVE CCA bifurcation (superior to carotid sinus)
glossopharyngeal nerve (CN IX)
monitors pO2 via peripheral chemoreceptors (O2 levels in blood)
(carotid body + aortic arch = chemoreceptors)
contents of carotid sheath?
common carotid artery (medial)
IJV (lateral)
vagus nerve (posterior)
function of the hyoid bone?
provides attachment for suprahyoid muscles superior and infrahyoid muscle inferiorly
function of hyoid muscles?
move + stabillise hyoid bone (therefore larynx) during chewing, swallowing and speaking
what are the suprahyoid muscles?
mylohyoid
geniohyoid
stylohyoid
digastric
where are the suprahyoid muscles?
hyoid to cranium
function of suprahyoid muscles?
support hyoid - allowing tongue to function
elevate hyoid and larynx in relation to swallowing and (muscle) tone production (helps oesophageal sphincter to open)
where do suprahyoid muscles arise?
mandible from floor of mouth
what are infrahyoid muscles also known as?
strap muscles
function of infrahyoid muscles?
depress + stabilise hyoid bone during swallowing + speaking
infrahyoid muscles?
sternohyoid
omohyoid
sternothyroid
thyrohyoid
innervation of infrahyoid muscles?
C1-3: sternohyoid, omohyoid, sternothyroid (cervical plexus)
thyrohyoid: hypoglossal nerve (CN XII)
why does a goitre not extend upwards?
STERNOthyroid covers the lateral lobe of thyroid cartilage
and attaches to an oblique line
what happens to the infrahyoid muscles during thyroidectomy?
infrahyoid muscles retracted to side as they lie immediately anterior to thyroid gland
what is the anterior cervical region?
contains carotid system of arteries, has branches of CCA + terminal branches
where does the CCA bifurcate?
superior border of thyroid cartilage (C4)
where does the ICA enter cranium?
through carotid canal as it has no branches in the neck
what does the ECA supply?
most structures of external cranium (with supraorbital arteries)
where does the ECA run?
embedded within parotid gland to give off terminal branches: maxillary + superficial temporal
non-terminal branches of ECA?
(inferior to superior): posterior auricular artery superior thyroid artery ascending pharyngeal artery lingual artery facial artery occipital artery
venous drainage of H+N?
mainly IJV
what is the main nerve of the anterior cervical region?
hypoglossal nerve (CN XII) motor innervation of tongue
course of travel of hypoglossal nerve (CN XII)
enters submandibular triangle deep to posterior belly of digastric to supply intrinsic + extrinsic (4/5) muscles of tongue
palatoglossus by vagus
where is the thyroid gland?
deep to sternothyroid and sternohyoid (infrahyoid) muscles
in anterior neck at C5-T1
how is the thyroid gland in relation to other structures?
wraps around the cricoid cartilage
sits inferior to larynx
each lobe extends up to oblique line (inferior) of thyroid cartilage (just below C5 + C6)
where is the cricoid cartilage?
inferior to thyroid cartilage at C6
what is the thyroid gland bounded by?
pretracheal fascia
what is contained within the pretracheal fascia?
trachea
oesophagus
pharynx
thyroid
why does the thyroid move up during swallowing?
pre-tracheal fascia attaches thyroid to trachea + larynx
larynx elevates during swallowing (suprahyoid muscles)
pulling pre-trachea fascia with it and therefore thyroid
(suprahyoid –> hyoid –> larynx –> pre-tracheal fascia –> thyroid)
posterior thyroid attached to cricoid cartilage by thickening of pretracheal fascia (ligament of berry / suspensory ligament)
what does the thyroid gland consist of?
2 lobes anterolaterally to larynx + trachea
central isthmus over trachea (bifurcates during descent from foramen cecum)
where do thyroid swellings grow? why? what can it lead to?
posteriorly
(pre-tracheal) fascia forms outer false capsule of thyroid
the posterior aspect is thin and not well defined
can compress oesophagus causing dysphagia
blood supply of thyroid
thyroid = highly vascularised, secretes hormones directly into blood
superior + inferior thyroid arteries (Extensive ANASTOMOSES)
where is superior thyroid artery from? supply?
1st branch of ECA, descends to superior pole of gland and divides into anterior + posterior branches
where are the inferior thyroid arteries from? supply?
thyrocervical trunk (from subclavian artery) supplies inferior + posterior poles of gland
innervation of thyroid gland?
branches form sympathetic trunk
do NOT control endocrine secretion
what regulates the hormone release of thyroid gland?
pituitary gland
which structure runs close to the superior thyroid artery?
external branch of superior laryngeal nerve runs posterior to superior thyroid artery
where do the left and right recurrent laryngeal nerve hook?
left: under arch of aorta
right: around right subclavian artery
course of travel of recurrent laryngeal nerves?
from respective vagus nerves, descend into chest, ascending back up into neck (pass between trachea and oesophagus, underneath thyroid) to innervate larynx
(can be compressed in goitre? thyroid pathologies - hoarseness of voice, also larynx pathologies)
venous drainage of trachea?
from superior thyroid (drains to IJV) middle thyroid (drains to IJV) inferior thyroid vein (drain into brachiocephalic vein)
where are the parathyroid glands located?
lie external to the thyroid capsule (pre-tracheal fascia) on posterior of thyroid gland
(normally 4 separate glands)
