Neck: posterior triangle Flashcards
boundaries of anterior triangle?
roof: investing cervical fascia
anterior: line from symphysis menti to sternal notch
posterior: SCM
superior: inferior margin of mandible
floor: viscera of neck
What are the suprahyoid muscles?
digastric m.
stylohyoid
mylohoid
what are the “strap” muscles?
sternohyoid
sternothyroid
thyrohyoid
omohyoid
digastric muscles
two bellied muscle with intermediate tendon, tethered to hyoid via fascial sling
O: anterior: mandible
posterior: mastoid notch
I: hyoid bone via fascial sling
A: elevates hyoid bone and base of tongue; with hyoid fixed via infrahyoid musculature is assists in opening mouth
N: ant: mylohyoid n (CN V3)
post: digastric branch of facial n. (CN VII)
stylohoid
O: styloid process
I: hyoid bone
A: elevates and retracts hyoid and base of tongue allowing for swallowing
N: digastric branch of facial n (CN VII)
mylohyoid
O: both sides of mandible
I: midline raphe from symphysis menti to hyoid bone
A: depresses hyoid and larynx
N: ansa cervicalis
sternohyoid
O: sternum
I: hyoid
A: depresses hyoid and larynx
I: ansa cervicalis
which two muscles are deep strap muscles and superficial strap muscles?
superficial: sternohyoid, omohyoid
deep: sternothyroid, thyrohyoid
sternothyroid:
O: sternum
I: thyroid cartilage
A: depresses larynx
I: ansa cervicalis
thyrohyoid:
O: thyroid cartilage
I: hyoid
A: depresses hyoid and tongue when larynx is fixed from below; elevates larynx when hyoid is fixed from above
I: C1 from hypoglassal n.
omohyoid
- two bellied muscle with tendon sling attached to clavicle
O: superior: hyoid
inferior: superior margin of scapula
I: infrahyoid fascia to clavicle and first rib
A: stabilizes, retracts and depresses hyoid and larynx
N: ansa cervicalis
what does thyroid gland do?
endocrine gland:
- follicular cells secrete thyroxin (controls metabolic rate)
- parafollicular “C” cells: secrete calcitonin which decreases circulating Ca2+ levels
anatomy of thyroid gland?
- located posterior to sternohyoid and sternothyroid muscles
- extends from thyroid cartilage to 6th tracheal ring
- two lobes are attached by an isthmus
- surrounded by pretracheal fascia
pyramidal lobe
may exist at junction of isthmus with left lobe extending superiorly toward hyoid. this lobe marks the descend o fthe thyroid primordium.
- in absence of pyramidal lobe, ectopic glandular tissue may remain active along this route and may form thyroglossal duct cysts
what arteries supply the thyroid gland?
- superior thyroid a.
- superior laryngeal a. anterior and posterior branch - inferior thyroid a.
- thyroid ima artery (only 10%)
superior thyroid a.
branch from external carotid a.
- superior laryngeal a: pierces thyrohyoid membrane with internal laryngeal n (vagus) to provide branches to interior of larynx
- anterior branch. supply anterior portion of thyroid gland, anastamose with opposite counterpart
- posterior branch: supply posterior of gland and anastamose with branches of inferior thyroid artery
- anterior branch
- posterior branch
inferior thyroid artery
branch of thyrocervical trunk (1st part of subclavian artery)
- ascends along anterior scalene muscles
- goes behind carotid sheath and symp trunk at level of thyroid cartilage
- anastamoses with posterior branches of superior artery
thyroid ima artery
variable unpaired branch of brachiocephalic coming directly from aortic arch
- in 10% of pop
- ascends the ventral surface of trachea to gain thyroid isthemus
- anastamoses with inferior thyroid aa.
- note: care must be taken in tracheostomy midline incisions if it is present
how does thyroid drain?
1/2: superior/middle thyroid vv. drain to right and left IJV
3. inferior thyroid vv. BOTH drain to left subclavian v. (as well as thyroid ima v. if it is present)
lymphatic drainage of thyroid?
lymph from thyroid first drains to judtavisceral nodes: prelaryngeal, paratracheal and pretracheal lymph nodes which are lcoated midline
- lymph then drains to superior deep cervical nodes from upper half, and inferior deep cervical nodes
- all lymph ultimately drains to DEEP CERVICAL LYMPH NODES
how is the thyroid innervated?
- preganglionic symp fibers come from T1-4
- postganglionic symp fibers travel from superior, middle and cervicothoraciv ganglia via sympathetic cardiac nerves
anatomy of parathyroid glands?
- 2-6 flattened ovoid bodies on dorsal surface of thyroid.
- secrete PTH which is imp. for balancing skeletal calcium levels
- shares thyroid gland blood supply
*note: removal of PTH leads to tetany and death
Trachea
continuation of airway below cricoid cartilage and larynx
- composed of incomplete cartilaginous rings that are closed posteriorly by trachealis muscle (ANS muscle that regulates tracheal diameter)
- blood supply: inferior thyroid aa.
- venous drainage: inferior thyroid vv.
- lymph drainage: juxtavisceral nodes (pre and para tracheal and inferior deep cervical nodes)
Esophagus
extends from cricoid cartilage and descends to the left
- covered posteriorly by pre-vertebral fascia
- blood supply: inferior thyroid aa. and vv.
- lymph: drained by paratracheal and inferior deep cervical lymph nodes
