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