Head and Neck, Session 2 Flashcards
Why is the left common carotid artery longer than the right?
left derived from arch of aorta, and so courses for about 2cm in superior mediastinum before entering neck, whereas right from brachiocephalic artery where bifurcates behind r sternoclavicular joint
what is the course of the common carotid artery defined as?
carotid line: defined by a line beginning below sternoclavicular joint and terminating midway between angle of mandible and mastoid process of temporal bone.
where does the external carotid artery divide into maxillary and superficial temporal branches?
at a level behind neck of mandible, within substance of parotid gland
here it is accompanied by the facial nerve and the retromandibular vein
reliable anatomical landmark for birfurcation on common carotid artery?
superior border of thyroid cartilage
carotids terminate midway between angle of mandible and mastoid process of temporal bone
where does the inferior thyroid artery originate from?
thyrocervical trunk- comes off subclavian artery
branches of external carotid artery?
superior thyroid lingual facial ascending pharyngeal occipital posterior auricular
terminal: superficial temporal
maxillary
clinical relevance of carotid triangle?
carotid pulse
access vagus and hypoglossal (XII) nerves
carotid end arterectomy, surgical approach to carotid artery or IJV
carotid sinus massage e.g. in supraventricular tachycardia
why can a cut to the scalp lead to profuse bleeding?
arteries supplying scalp lie in dense CT which is closely attached to the walls of the arteries, limiting their constriction
why is scalp bleeding predominantly arterial?
venous pressure extremely low in erect position
arteries have limited ability to constrict when lacerated due to close attachment of their walls with dense CT
what is an extradural hamatoma?
bleeding into the extradural space- potential space between dura mater and bone, periosteal layer of dura normally firmly attached to bones surrounding outside of cranial cavity, but can become fluid-filled space with haemorrhage e.g. laceration of middle meningeal artery or a torn dural venous sinus
how might an infection of the scalp spread to involve the meninges?
blood can flow from the veins of the scalp into the diploic veins of the skull, and then into the dural venous sinuses, due to emissary veins connecting veins of scalp to diploic veins
what does the facial artery supply?
muscles of facial expression and face
what does the superior labial artery supply?
upper lip, and side and septum of nose
what does inferior labial artery supply?
lower lip
what does lateral nasal artery supply?
skin on ala and dorsum of nose
what does angular artery supply?
superior part of cheek and inferior eyelid
what does occipital artery supply?
scalp of back of head, as far as vertex
what does posterior auricular artery supply?
scalp post to auricle and auricle
what does superficial temporal artery supply?
facial muscles, and skin of temporal frontal and temporal regions
what does the transverse facial artery supply?
parotid gland and duct, muscles and skin of face
what does mental artery supply?
facial muscles and skin of chin
what does supra-orbital and supratrochlear arteries supply?
muscles and skin of forehead, and scalp and superior conjunctiva
which arteries supply blood to the brain?
internal carotid
vertebral
what is the carotid sheath made from?
areolar (LCT) tissue
what is the carotid sheath derived from?
fusion of prevertebral layer of fascia posteriorlu, pretracheal anteromedially, and superficial layer of cervical fascia anterolaterally
where does the sympathetic trunk lie in relation to the carotid sheath?
outside sheath, medially and behind it
major source of blood to extra-cranial structures?
external carotid artery
where are the superficial cervical LNs situated?
along the course of the EJV
LNs in regional group of head and neck?
occipital, retroauricular, submandibular, submental, anterior, cervical, superficial cervical, retropharyngeal, laryngeal and tracheal
give examples of 2 deep (terminal) cervical LNs, and what they drain?
jugulo-digastric: located just below and behind angle of mandible, drains tongue and tonsil
jugulo-omohyoid: drainage of tongue, oral cavity, trachea, oesophagus, and thyroid gland
what do the efferent lymph vessels from deep cervical nodes join to form?
the jugular lymph trunks
what do the jugular lymph trunks join with on the L side?
throacic duct, which enters the L brachiocephalic vein at junction of subclavian and internal jugular vein
what do the jugular lymph trunks join with on the R side?
enters venous system at junction between subclavian and IJV via a short right lymphatic duct
What does a surgeon do when cervical metastases occur?
performs a block dissection of cervical nodes, removing en bloc the IJV, fascia, LNs and submandibular salivary gland.
Aim to remove all lymph tissues on affected side of enck
where is the carotid body located in relation to the division of the common carotid artery?
just posterior to it
how specifically can the common carotid artery pulse be felt?
by pressing against the anterior tubercle of transverse process of C6 vertebra.
Also at point of division of artery- vertebral level C4- upper border of thyroid cartilage
Can be felt just medial to SCM
why must carotid artery palpation be performed low in neck?
to avoid pressure on carotid sinus which could cause a reflex drop in heart rate and blood pressure
Why is the right IJV evaluated rather than the left?
the right is straighter
why are pulsations of IJV visible?
transmitted through surrounding tissue
worry if sudden occurrence of a stiff neck, with fever and headache?
meningtitis
what might neck pain be associated with because of referred pain?
MI or angina, as referred pain from chest
muscles derived from first pharyngeal arch?
muscles of mastication- temporalis, masseter, medial and lateral pterygoids mylohyoid anterior belly of digastrics tensor tympani tensor veli palatine
cranial nerve of first pharyngeal arch?
trigeminal (V)- maxillary and mandibular divisions
mandibular branch supplies muscles of arch
principal sensory nerve of head- skin of face, and lining of mouth and nose
motor to muscles of mastication and those derived from mandibular process
cranial nerve of second pharyngeal arch?
facial nerve (VII)
what does facial nerve pass through?
stylomastoid foramen and parotid gland
supplies muscles of facial expression, and those derived from 2nd pharyngeal arch
small sensory component of facial nerve?
taste buds in anterior 2/3 of tongue
why might thyroid surgery result in vocal cord paralysis?
damage to recurrent laryngeal nerves
name of oblique plane where curvature of aorta starts and ends?
transverse thoracic plane
clinical importance of jugulo-omohyoid internal jugular LN which lies above the omohyoid muscle?
can be enlarged in oral cancer
why might a patient have difficulty turning their head and shrugging their shoulders if they have had their spinal accessory nodes (part of deep group) removed?
these nodes lie in the posterior triangle of the neck, along course of accessory nerve, and removal due to malignancy may damage the accessory nerve , causing weakness in SCM and trapezius
examples of deep cervical LNs?
internal jugular
spinal accessory
supraclavicular
where does the thoracic duct arise?
from cisterna chyli in the abdomen at L2, ascends through aortic hiatus at T12 in diaphragm, crosses midline at T5 to the left, post to oesophagus and ascends into superior medistinum
where does thoracic duct empty into venous system?
at left venous angle- where union of left internal jugular and subclavian veins
may enter origin of left brachiocepahlic vein
or may empty directly into left subclavian vein
how are the pharyngeal clefts and pouches separated?
branchial (pharyngeal) membrane- thin sheet of ectoderm on outside, and endoderm on inside
how may branchial cysts in the neck be formed?
A flap of tissue from the second pharyngeal arch grows down to cover the third to sixth arches and clefts, obliterating all other clefts except 1st, creating a space, the Cervical Sinus. This is normally obliterated, but remnants of clefts may persist as branchial cysts in the neck if it is not.
can occur anywhere along A border of SCM- path taken by 2nd pharyngeal arch
cranial nerves innervating pharyngeal arches?
CN V, VII, IX and X
muscles of 2nd pharyngeal arch?
muscles of facial expression
poster. belly of digastrics
stylohyoid
stapedius
nerve of 3rd pharyngeal arch?
glossopharyngeal
muscle of 3rd pharyngeal arch?
stylopharyngeus
nerve of 4th to 6th pharyngeal arches?
vagus: superior laryngeal to 4th, recurrent laryngeal to 6th
muscles of 4th pharyngeal arch?
cricothyroid, levator palatini, constrictors of pharynx
muscles of 6th pharyngeal arch?
intrinsic muscles of larynx
general and special sensory innervation of glossopharyngeal nerve?
posterior 1/3 of tongue
what cells are the skeletal elements of the head and neck derived from?
neural crest cells
name of 1st pharyngeal arch cartilage?
Meckel’s cartilage
derivatives of 1st pharyngeal arch cartilage?
malleus and incus- middle ear bones
sphenomandibular ligament
template for mandible which forms by intramemebranous ossification, so cartilage not converted into bone
2nd pharyngeal arch cartilage?
Reichert’s cartilage
skeletal element derivatives of 2nd pharyngeal arch?
stapes- bones of middle ear
styloid process of temporal bone
stylohyoid ligament
lesser cornu and upper body of hyoid
skeletal element derivative of 3rd pharyngeal arch?
greater cornu and part of body of hyoid
skeletal element derivatives of 4th and 6th pharyngeal arch catilages?
thyroid, arytenoid and cricoid cartilages of larynx
what is the epiglottis derived from?
4th and 6th pharyngeal arch mesenchyme from the pharyngeal floor
what provides arterial supply to pharyngeal arches?
aortic arches
3rd aortic arch artery?
internal carotid
4th aortic arch arteries?
arch of aorta on left, brachiocephalic artery on right
6th aortic arch artery?
pulmonary arch
On R, distal part of 6th aortic arch and 5th disappear, so R recurrent laryngeal nerve moves up and hooks around R subclavian vein
L nerve does not move up as distal part of 6th aortic arch persists as ductus arteriosus
derivative of 2nd pharyngeal pouch?
palatine tonsils- 2nd pouch epithelial proliferation, followed by colonisation by lymphoid precursors
what are the parathyroid glands derived from?
the 3rd (forms inferior) and 4th (forms superior) dorsal pharyngeal pouches
what is the thymus gland derived from?
the 3rd ventral pharyngeal pouch
1st pharyngeal pouch derivatives?
tympanic cavity and eustachian tube
remember, ossicles= 1st and 2nd arch cartilage bar derivatives
outcome of 1st pharyngeal cleft?
external acoustic meatus
how are the eyes shifted from sides of head to front?
growth of maxillary prominences towards midline
what are the tympanic cavity and eustacian tube of middle ear derived from?
1st pharyngeal pouch
how is the facial vein connected to the cavernous sinus?
via the superior opthalmic vein
importance of facial vein being valveless?
infection of face can spread to involve venous sinuses, as facial vein connected to cavernous sinus
veins which form the external jugular vein?
union of posterior auricular and retromandibular (posterior branch) veins
what are the layers of the scalp?
SCALP:skin, CT-vessels and nerve, aponerurosis-epicranial between occipital and frontalis muscles, LCT, periosteum (pericranium)
