10 self-study: hyoid muscles + thyroid

Question 1

boundaries of anterior triangle?

Answer 1

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

Question 2

borders of carotid triangle?

Answer 2

superior: posterior belly of digastric
medial: superior belly of omohyoid
lateral: anterior border SCM

Question 3

how can carotid pulse be felt?

Answer 3

by pressing lightly against the anterior tubercle of the transverse process of C6

Question 4

where is carotid sinus? innervation? function?

Answer 4

dilation of proximal ICA
glossopharyngeal nerve (CN IX)
detect changes in arterial BP by baroreceptors 
(carotid sinus + aortic arch = baroreceptors)

Question 5

where is the carotid body? innervation? function?

Answer 5

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)

Question 6

contents of carotid sheath?

Answer 6

common carotid artery (medial)
IJV (lateral)
vagus nerve (posterior)

Question 7

function of the hyoid bone?

Answer 7

provides attachment for suprahyoid muscles superior and infrahyoid muscle inferiorly

Question 8

function of hyoid muscles?

Answer 8

move + stabillise hyoid bone (therefore larynx) during chewing, swallowing and speaking

Question 9

what are the suprahyoid muscles?

Answer 9

mylohyoid
geniohyoid
stylohyoid
digastric

Question 10

where are the suprahyoid muscles?

Answer 10

hyoid to cranium

Question 11

function of suprahyoid muscles?

Answer 11

support hyoid - allowing tongue to function

elevate hyoid and larynx in relation to swallowing and (muscle) tone production (helps oesophageal sphincter to open)

Question 12

where do suprahyoid muscles arise?

Answer 12

mandible from floor of mouth

Question 13

what are infrahyoid muscles also known as?

Answer 13

strap muscles

Question 14

function of infrahyoid muscles?

Answer 14

depress + stabilise hyoid bone during swallowing + speaking

Question 15

infrahyoid muscles?

Answer 15

sternohyoid
omohyoid
sternothyroid
thyrohyoid

Question 16

innervation of infrahyoid muscles?

Answer 16

C1-3: sternohyoid, omohyoid, sternothyroid (cervical plexus)

thyrohyoid: hypoglossal nerve (CN XII)

Question 17

why does a goitre not extend upwards?

Answer 17

STERNOthyroid covers the lateral lobe of thyroid cartilage

and attaches to an oblique line

Question 18

what happens to the infrahyoid muscles during thyroidectomy?

Answer 18

infrahyoid muscles retracted to side as they lie immediately anterior to thyroid gland

Question 19

what is the anterior cervical region?

Answer 19

contains carotid system of arteries, has branches of CCA + terminal branches

Question 20

where does the CCA bifurcate?

Answer 20

superior border of thyroid cartilage (C4)

Question 21

where does the ICA enter cranium?

Answer 21

through carotid canal as it has no branches in the neck

Question 22

what does the ECA supply?

Answer 22

most structures of external cranium (with supraorbital arteries)

Question 23

where does the ECA run?

Answer 23

embedded within parotid gland to give off terminal branches: maxillary + superficial temporal

Question 24

non-terminal branches of ECA?

Answer 24

(inferior to superior):
posterior auricular artery
superior thyroid artery
ascending pharyngeal artery
lingual artery
facial artery
occipital artery

Question 25

venous drainage of H+N?

Answer 25

mainly IJV

Question 26

what is the main nerve of the anterior cervical region?

Answer 26

``` hypoglossal nerve (CN XII) motor innervation of tongue ```

Question 27

course of travel of hypoglossal nerve (CN XII)

Answer 27

enters submandibular triangle deep to posterior belly of digastric to supply intrinsic + extrinsic (4/5) muscles of tongue palatoglossus by vagus

Question 28

where is the thyroid gland?

Answer 28

deep to sternothyroid and sternohyoid (infrahyoid) muscles | in anterior neck at C5-T1

Question 29

how is the thyroid gland in relation to other structures?

Answer 29

wraps around the cricoid cartilage sits inferior to larynx each lobe extends up to oblique line (inferior) of thyroid cartilage (just below C5 + C6)

Question 30

where is the cricoid cartilage?

Answer 30

inferior to thyroid cartilage at C6

Question 31

what is the thyroid gland bounded by?

Answer 31

pretracheal fascia

Question 32

what is contained within the pretracheal fascia?

Answer 32

trachea oesophagus pharynx thyroid

Question 33

why does the thyroid move up during swallowing?

Answer 33

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)

Question 34

what does the thyroid gland consist of?

Answer 34

2 lobes anterolaterally to larynx + trachea | central isthmus over trachea (bifurcates during descent from foramen cecum)

Question 35

where do thyroid swellings grow? why? what can it lead to?

Answer 35

posteriorly (pre-tracheal) fascia forms outer false capsule of thyroid the posterior aspect is thin and not well defined can compress oesophagus causing dysphagia

Question 36

blood supply of thyroid

Answer 36

thyroid = highly vascularised, secretes hormones directly into blood superior + inferior thyroid arteries (Extensive ANASTOMOSES)

Question 37

where is superior thyroid artery from? supply?

Answer 37

1st branch of ECA, descends to superior pole of gland and divides into anterior + posterior branches

Question 38

where are the inferior thyroid arteries from? supply?

Answer 38

``` thyrocervical trunk (from subclavian artery) supplies inferior + posterior poles of gland ```

Question 39

innervation of thyroid gland?

Answer 39

branches form sympathetic trunk | do NOT control endocrine secretion

Question 40

what regulates the hormone release of thyroid gland?

Answer 40

pituitary gland

Question 41

which structure runs close to the superior thyroid artery?

Answer 41

external branch of superior laryngeal nerve runs posterior to superior thyroid artery

Question 42

where do the left and right recurrent laryngeal nerve hook?

Answer 42

left: under arch of aorta right: around right subclavian artery

Question 43

course of travel of recurrent laryngeal nerves?

Answer 43

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)

Question 44

venous drainage of trachea?

Answer 44

``` from superior thyroid (drains to IJV) middle thyroid (drains to IJV) inferior thyroid vein (drain into brachiocephalic vein) ```

Question 45

where are the parathyroid glands located?

Answer 45

lie external to the thyroid capsule (pre-tracheal fascia) on posterior of thyroid gland (normally 4 separate glands)