Neck: Area under the SCM Flashcards
what is contained in carotid sheath?
common and internal jugular aa.
internal jugular v.
vagus. n
superior root of ansa cervicalis (inferior root is on its lateral surface)
where are things located in the carotid sheath?
- within the sheath the artery is medial and anterior, vein is lateral and posterior
- vagus n. descends posterior groove between the two vessels
- ansa cervicalis
common carotid aa.
- left side is longer than the right side and comes directly off of aorta
- right side originates at brachiocephalic split from arch of aorta
- splits into internal and external carotid aa.
- has no branches, though sometimes the superior thyroid a. will slide down to common carotid during development
carotid sinus
located at dilated distal common carotid and proximal internal carotid; pressure receptor
- increase in P = decrease in HR
carotid body
located at the carotid bifurcation; chemoreceptor
- senses changes in O2
- decrease in O2=> increase in rate and depth of respiration
internal carotid artery
- enters base of skull at carotid canal
- has no branches before the brain
- in brain it supplies the orbit and the brain
external carotid artery : 8 branches?
- gives off first four branches near the bifurcation:
1. superior thyroid
2. ascending pharyngeal a.
3. lingual a.
4. facial a. - ascends and crosses laterally by posterior belly of digastric and stylohyoid where gives off two more branches:
5. occipital a.
6. posterior auricular a. - terminates near neck of mandible:
7. maxillary a.
8. superficial temporal a.
how do surgeons gain access to carotid bifurcation?
access via carotid triangle: anterior border of SCM, post. border of sup. belly of omohyoid, inferior border of post. belly digastric
- this approach can be used to remove atherosclerotic plaque “ carotid endarterectomy”
superior thyroid a.
1st branch - courses along superior medial margin of thyroid gland, gives off: superior laryngeal a. anterior branch posterior branch
ascending pharyngeal a.
2
- arises from medial aspect of externa carotid usually near bifurcation
- travels straight to base of skull
lingual artery
#3 usually arises opposite greater horn of hyoid - passes deep to hypoglossus muscle to enter tongue and give branches
facial a.
#4 may arise off common trunk with lingual a. - courses obliquely and around inferior border of mandible at anterior edge
occipital a.
#5 passes posteriorly to external carotid artery at inferior border of posterior belly of digastric to pass between transverse process of atlas and mastoid process - pierces cervical fascia where trapezius and SCM come togetherto enter the scalp
Note: hypoglassal n. crosses the occipital a. at its origin from external carotid
posterior auricular a.
passes psoteriorly to external carotid a. at superior border of posterior belly of digastric to course posterior to auricle
what are two final branches of external carotid a?
maxillary and superficial temporal aa.
internal jugular vv.
- largest v. of head and neck
- receives blood from brain, face, neck via dural venous sinuses
- begins as superior jugular bulb at jugular foramen
- as it descends the carotid sheath it lies superiorly and posterolaterally.
- ends in inferior bulb where it joins subclavian v. to form brachiocephalic v.
what does vagus nerve supply?
CN X
SVE, SVA, GVA, GSA, GVE-P: largest cranial n.
- PS to heart, lungs and digestive (GVE-P)
- motor to striated muscles of pharynx, palate, larynx, prox 1/3 esophagus (SVE)
- general sensation (GVA) to carotid body epiglottis, larynx, resp. system and GI
- special sensation (GSA) to external ear, TM and posterior cranial fossa dura mater
- special taste to epiglottic portion of tongue (SVA)
where does vagus originate and course?
- originates at medulla
- exits skull via jugular foramen
- courses in carotid sheath, in between carotid a. and IJV
- while in retropharyngeal region it communicates with CN IX, XI, and XII and spinal nerves C1 and C2
what are branches of the vagus nerve?
- meningeal branch (goes to dura of posterior cranial fossa, gives GSA)
- auricular : (GSA) - to pinna and auditory canal and TM
- pharyngeal: (SVE) muscles of pharynx and soft palate
- nerve to carotid body: (GVA): from chemoreceptors
- superior laryngeal n.
- cervical cardiac branches
- recurrent laryngeal n
superior laryngeal n.
- passes obliquely from superior portion of vagus to larynx traveling medial to carotid sheath
- provides internal branch (SVA, GVA, GVE-P)- and external branch (SVE)
external branch of laryngeal n.
(SVE)- courses lateral to pharynx and larynx on inferior constrictor muscle along with superior thyroid artery. courses medially at thyroid cartilage to innervate cricothyroid muscle and inferior constrictor muscle.
internal branch of laryngeal n.
(SVA, GVA, GVE-P)- pierces the thyrohyoid membrane to provide sensory fibers (taste and general sensation) and PS to the base of tongue (mucous glands), epiglottic and internal portion of larynx above true vocal fold
cervical cardiac branches
branches of vagus nerve (GVE-P, GVA)
- superior cardiac nn: arise near origin of superior laryngeal n. and descend medial to carotid sheath
- inferior cardiac nn: arise from vagus in root of neck near first rib
- both superior cardiac nn.and rt inferior cardiac nn. form the deep cardiac plexus. left inferior cardiac n. joins the superficial cardiac plexus.
recurrent laryngeal n.
(SVE, GVE-P, GVA) - recurs near root of neck
- on right side recurs around subclavian, on left it recurs around the aortic arch at the ligamentum arterioosum
- both will go to the larynx
- motor innervation to larynx (SVE)
- secretory mucous (GVE-P)
- sensory to mucosa inferior to vocal folds (GVA)
