head and neck anatomy Flashcards
Blood supply to the brain
What are the main arteries contributing to the blood supply of the brain?
● Posteriorly, the vertebral arteries merge to form the basilar artery
● Internal carotid arteries
● These anastamose via the anterior and posterior communicating arteries to form
the Circle of Willis
What are the main cerebral arteries and which lobes of the brain do they supply?
● Some overlap in lobar supply
● Anterior cerebral artery - frontal, parietal lobes
● Middle cerebral artery - frontal, lateral temporal, parietal lobes
● Posterior cerebral artery - medial temporal, parietal, occipital lobes
What motor and sensory areas lie in the distribution of the middle cerebral artery?
● Motor and sensory areas of the contralateral side of the body except the legs and
perineum
● Auditory and speech areas
Which vessels make up the posterior circulation?
● Posterior cerebral artery
● Superior cerebellar arteries
● Anterior and posterior inferior cerebellar arteries
● Pontine arteries
What areas of the brain do the main arteries of the posterior circulation supply?
● Vertebral arteries supply the cranial meninges and cerebellum
● Basilar arteries supply the brainstem, cerebellum and cerebrum
● Posterior cerebral arteries supply the inferior aspect of the cerebral hemispheres
and occipital lobe
● Posterior communicating arteries supply the optic tract, cerebral peduncle,
internal capsule and thalamus
Describe the venous drainage of the cerebral hemispheres.
● Superior cerebral veins drain the superolateral surface of the brain → superior
sagittal sinus
● Inferior and superficial middle cerebral veins drain the inferior, posterior and deep
aspects of the cerebral hemispheres→ straight, transverse and superior petrosal
sinuses
● Great cerebral vein → merges with inferior sagittal sinus to form the straight
sinus
● Eventually these terminate in the internal jugular veins
Skull
Identify the bones and sutures of the cranial vault
● Frontal bone
● Parietal bone
● Occipital bone
● Temporal bone
● Sphenoid bone
● Coronal suture
● Sagittal suture
● Lambdoid suture
What are the major bony compartments within the base of the skull?
● Anterior cranial fossa - formed by the frontal bone, ethmoid bone and lesser wing
of the sphenoid
● Middle cranial fossa - formed by the sphenoid and squamous temporal bones
laterally. Contains the sella turcica
● Posterior cranial fossa - occipital bone, sphenoid.
Identify the foraminae in the base of the skull
● From anterior to posterior
● Cribriform plate - olfactory nerve
● Optic canal - optic nerve and ophthalmic artery
● Superior orbital fissure - oculomotor, trochlear, ophthalmic division of the
trigeminal and abducens
● Foramen lacerum - internal carotid artery
● Internal acoustic meatus - cranial nerve VII, VIII
● Foramen rotundum - V2 ( Maxillary) “maximally rotund”
● Foramen ovale - V3 (mandibular) because ovale is like the shape of an open
mouth - mandible
● Foramen spinosum - middle meningeal artery
● Foramen magnum - medulla/brainstem plus the vertebral arteries, CNXI,
● Jugular foramen - CN IX, X, XI and the internal jugular vein
● Hypoglossal canal - CN XII
Cranial Nerves
What is the nerve supply to the extraocular muscles?
Cranial nerve III - oculomotor
● superior , inferior, medial rectus muscles, inferior oblique,
● Levator palpebrae superioris
● Parasympathetic supply through ciliary ganglion to smooth muscle of the
sphincter pupillae and ciliary muscle
Cranial nerve IV - Trochlear
● Superior oblique
Cranial nerve VI - Abducens
● Lateral rectus
What is the effect of a complete third nerve lesion?
● Resting position becomes a depressed/abducted eye
● Ptosis
● Dilated pupil
What is the effect of a 4th nerve lesion?
● Loss of superior oblique
● Inability to look down while looking in
● Extorsion - compensate by tilting to the opposite shoulder
What are the branches of the trigeminal nerve?
Arises from the pons (an easy way to remember is the first 4 CN’s arise above the pons
(CN I - IV), the next 4 arise from the pons itself (CNV-VIII) and then the last 4 arise
below the pons (CN IX-XII)
● Ophthalmic (V1) sensory - smallest, goes via supraorbital fissure
● Maxillary (V2) sensory
● Mandibular (V3) sensory & motor
Describe the motor and sensory distribution of the trigeminal nerve
Motor
● Muscles of mastication (masseter, temporalis, medial pterygoid, lateral pterygoid)
● Mylohyoid
● Anterior belly of digastric
● Tensor tympani
● Tensor veli palatini
Sensory
● Skin of face and anterior scalp
● eyelids/cornea/conjunctiva
● nose/mucosa of nasal cavity
● Paranasal sinuses
● Ear
● mouth/lip/gingiva/palate
● Tongue (general sensation anterior 2/3rds - facial does taste)
● Dura of anterior and middle cranial fossa
Intracranial structures
You will be shown an image of a head CT and be asked to describe some normal
structures
● Lobes: frontal, temporal, parietal occipital
● Lateral ventricles: anterior and posterior horns, 3rd ventricle
● Caudate nucleus, putamen
● Thalamus, internal capsule
● Septum pellucidum
● Falcx
Describe the circulation of CSF
● Formed in the choroidal epithelial cells in lateral, 3rd and 4th ventricles
● Flows from the lateral ventricles to the 3rd ventricle via the interventricular
foramina
● 3rd ventricle → 4th ventricle via the aqueduct
● Some CSF passes into the subarachnoid space via the median and lateral
apertures
● Most CSF passes into interpeduncular and quadrigeminal cisterns
● CSF from the various subarachnoid cisterns flows superiorly through the sulci
and fissures on medial and superolateral surfaces of the cerebral hemispheres
● Absorbed into the arachnoid granulations, especially those that protrude into the
superior sagittal sinus
What are the functions of CSF?
● Protects the brain by providing a cushion effect
● The buoyancy effect prevents compression of nerves and vessels
Describe the ventricular system of the brain
● Lateral ventricles with anterior and posterior horns are the largest. Each opens
into the 3rd ventricle via the interventricular foramen
● 3rd ventricle = slit like opening between two diencephalon halves
● Continues as cerebral aqueduct which connects the 3rd and 4th ventricles
● 4th ventricle = pyramid shaped, posterior part of the pons and medulla.
The eyes
Identify the extraocular eye muscles on this model
● Superior rectus
● Inferior rectus
● Medial rectus
● Lateral rectus
● Superior oblique
● Inferior oblique
Describe the action of eye muscles
Recti
● Superior (elevation, adduction, medial rotation)
● Inferior (depression, adduction, lateral rotation)
● Medial (adduction)
● Lateral (abduction)
Obliques
● Superior (depression, abduction)
● Inferior (elevation, abduction)
What nerve supplies the eye muscles?
● Oculomotor nerve
● Abducens nerve to the lateral rectus
● Trochlear nerve to the superior oblique
How are the actions of eye muscles tested clinically?
Abduction (lateral rectus)
When in abduction
● Elevation - superior rectus
● Depression - inferior rectus
When in adduction
● Elevation - inferior oblique
● Depression - superior oblique
Which bones form the walls of the orbit?
● Roof - orbital part of the frontal bone and posteriorly the lesser wing of the
sphenoid
● Medial - ethmoid with contributions from the frontal process nod the maxilla,
lacrimal and sphenoids
● Lateral - frontal process of zygomatic bone and the greater wing of sphenoid
● Floor - maxilla and partly by the zygomatic and palatine bone
What structures pass through the superior orbital fissure?
● Ophthalmic nerve (V1)
● Oculomotor nerve (CNIII)
● Trochlear (CNIV)
● Abducens nerve (VI)n
● Sympathetic fibres and ophthalmic veins
What is the course of the infra-orbital nerve?
● Continuation of the maxillary nerve (V2)
● Enters the orbit through the infraorbital fissures and travels in the infraorbital
groove
● Exits through the infraorbital foramen
● Distribution to the cheek, lower lid, lateral nose, upper lip and gums and
antero/inf nasal septum
What structures does the intra-orbital nerve innervate?
● Mucosa of maxillary sinuses
● Upper medial teeth
● Skin of the cheek
● Skin of lateral nose
● Skin/conjunctiva of inferior eyelid
● Anterior Inferior nasal septum
● Skin and oral mucosa of the upper lip
What are the muscles of facial expression?
● Orbicularis oculi
● Orbicularis oris
● Zygomaticus muscles
● Buccinators
The eyeball
Identify the structures of the eyeball
● Cornea
● Anterior chamber/lens/iris/ciliary body/limbus
● Vitreous body
● Choroid
● Sclera
● Retina
● Optic nerve and disc
Describe the formation and drainage of aqueous humour
● Production by ciliary processes
● Enters the posterior chamber
● Passes through the pupil t the anterior chamber
● Filters through the iridocorneal angle to the canal of schlemm
● Drains into the anterior scleral veins
The face
What is the arterial supply to the face?
● Facial artery- arises from the external carotid artery, contacts the submandibular
gland, hooks up over the mandible anterior to the masseter then takes a tortuous
course to the medial angle of the eye
● The transverse facial artery anastomoses with the above
What is the course and the branches of the facial nerve?
● Emerges through the temporal bone via the stylomastoid foramen
● Then divides into superior and inferior divisions
● Supplies the posterior auricular nerve
● Before entering the posterior medial surface of the parotid gland
● Within the parotid forms 5 branches
5 branches
● Temporal
● Zygomatic
● Buccal
● Marginal Mandibular
● Cervical
What is the function of the facial nerve?
● Motor supply of the face
● Muscles of facial expression
● Taste to the anterior 2/3rd of the tongue
● Skin at the external acoustic meatus
● Sublingual and submandibular glands
● Lacrimal glands
What is the sensory nerve supply of the face?
Trigeminal (5th cranial nerve) has 3 branches - ophthalmic, maxillary, mandibular
Mandible
What are the features of this bone?
Body, angle, ramus, condyle (includes the head and neck), coronoid process, pterygoid
fossa, mandibular notch, lingula, mylohyoid groove, submandibular fossa, sublingual
fossa, symphysis, mental protuberance, alveolar processes, mental tubercles, digastric
fossa
Describe the features of the temporomandibular joint
● Bones - condyle of the mandible, articular tubercle and the mandibular fossa
● Disc - separates superior synovial cavity (gliding in/out) and inferior synovial
cavity (hinge up/down)
● Postglenoid tubercle and temporomandibular (lateral) ligament prevent posterior
dislocation
● Stylomandibular and sphenomandibular ligaments are weak
What movements is the mandible capable of at the TMJ?
● Protrusion/retrusion
● Depression/elevation
● Lateral movement
What factors contribute to the stability of the TMJ?
● Shape of the TMJ
● Occlusion and teeth
● Stylomandibular ligament
● Sphenomandibular ligament
● Capsule of joint
● Muscles of mastication
Which nerve passes through the mandible bone?
● Inferior alveolar nerve
● Enters the mandibular foramen
● Within the mandible supplies mandibular teeth
● Exits the mental foramen as the mental nerve (supplies skin and mucous
membranes of the lower lip and skin of chin)
● The close relationship of this nerve to the bone makes it vulnerable to injury
What nerve does the inferior alveolar nerve arise from?
Mandibular nerve (V3- 3rd branch of the trigeminal nerve)
Describe the mandibular attachments of the muscles of mastication
● Temporalis - from the temporal fossa to the medial coronoid and anterior ramus
● Masseter - maxillary process and zygomatic arch to angle and lateral ramus
● Lateral pterygoid - greater wing sphenoid and lateral surface of the lateral
pterygoid plate to joint capsule, disc and pterygoid fossa on the neck of mandible
● Medial pterygoid - from the medial surface of the lateral pterygoid plate and the
tuberosity of the maxilla to medial ramus below the foramen
The tongue
What structures make up the floor of the mouth
Mandible, tongue, lip, teeth, geniohyoid muscle, hyoid bone, stylohyoid muscle,
genioglossus muscle
Describe the innervation of the tongue
● Motor - all muscles except the palatoglossus are supplied by cranial nerve XII,
the hypoglossal nerve. The palatoglossus is a palatine muscle so is supplied by
the pharyngeal plexus.
● General sensation to the mucosa of the anterior ⅔ of the tongue is supplied by
the lingual nerve, a branch of the CNV3
● Taste to the anterior ⅔ via the chorda tympani (from the facial nerve)
● Posterior ⅓ of the tongue, both general sensory and and taste supplied by the
lingual branch of the glossopharyngeal nerve
● Parasympathetic fibres via the chorda tympani supply the submandibular and
salivary glands
sensation of the ear
● What is the sensory supply to the pinna
● Greater auricular nerve (C2) cranial surface and lower half
● Auriculotemporal (from CNV3) supplies the upper half and most of the meatus
What other nerves supply the ear and the canal
● Lesser occipital
● Vagus
● Glossopharyngeal
● Facial nerve
What are the characteristics of a typical cervical vertebra?
● Small oval body with a large vertebral canal
● Concave on superior surface and convex on the inferior surface
● Spinous processes are short bifid and downward sloping (C7 usually not bifid)
● Facet joints are more horizontal to allow for greater movement
● Anterior and posterior transverse processes with a foramen transversum allowing
passage of the vertebral artery, vein and sympathetic plexus
Describe the joints between C1 and C2
● Two lateral atlanto axial joints - synovial joints, exist between the inferior articular
facet of the atlas and the superior articular facet of the axis on each side.
● Median atlanto-axial joint - synovial joint between the arch of C1 and the dens, it
is a pivot joint
What movements occur at the atlanto-axial joint?
Gliding at the lateral joints and pivoting at the median joint which permits rotation of the
head via rotation of C1 on C2
Which ligaments stabilise the joints between C1 and C12?
● Cruciate or cruciform ligament - made up of strong transverse ligament across
the atlas behind the dens and weaker vertical bands from the back of the body of
the axis, running posterior to the dens and attaching on the base of the occiput.
This holds the dens in position and prevents pressure from the dens onto the
medulla.
● 2 Alar Ligaments - run from the sides of the dens to the edge of the foramen
magnum. They are strong and limit rotation
● Tectorial membrane - a continuation of the posterior longitudinal ligament,
attached from the back of the body of the axis to anterior half of the foramen
magnum.
What are the boundaries of the anterior triangle of the neck?
Anterior border of the sternocleidomastoid, lower border of the mandible and the midline
Discuss the anatomy of the right common carotid artery
● Begins at the bifurcation of the brachiocephalic trunk behind the sternoclavicular
joint and into the common carotid and subclavian arteries
● In the neck it lies within the medial part of the carotid sheath, with the internal
jugular vein lateral to it and the vagus nerve deep between the two vessels.
● The common carotid bifurcates at the level of the upper border of the lamina of
the thyroid cartilage into the internal and external carotid arteries
Describe the surface marking of the internal jugular vein
From the masoid to the medial end of the clavicle
What major structures are at risk during insertion of an IJ line?
● External carotid artery
● Common carotid artery
● Vagus nerve (and other nerves)
● Lung
● Trachea
Thyroid
● SCM
Larynx - Note: Need to be able to identify key structures on the model - do this
What is the nerve supply to the muscles of the larynx?
Recurrent laryngeal nerve (from the vagus) supplies all muscles except the cricothyroid
muscle which i supplied by the external laryngeal nerve
larynx sensory innervation?
● Above the cords - internal laryngeal nerve which is a branch of the superior
laryngeal nerve
● Below the cords - recurrent laryngeal nerve, which is a branch of the inferior
laryngeal nerve
Demonstrate the landmarks for a surgical airway - cricothyrotomy
Thyroid cartilage, cricoid cartilage, cricothyroid membrane
Which cartilage of the larynx is fully circumferential?
Cricoid
What are the paired cartilages of the larynx?
Arytenoids, corniculates and cuneiforms
What are the muscles of vocalisation?
● Cricothyroid
● Thyroarytenoid
● Posterior cricoarytenoid
● Lateral cricoarytenoid
● Transverse and oblique arytenoids
● Vocalis
