Cranium and meninges Flashcards
How many bones in skull (excluding ossicles)
22
Outline the 3 overall bones
Cranium (make up base and vault)
Mandible
Facial skeleton (viscerocranium)
Name the bones of the cranium and the face
cranium: frontal (x2), parietal (x2), frontal, occipital, sphenoid, ethmoid
face: maxilla (x2), zygoma (x2), nasal (x2), lacrimal (x2), vomer, inferior conchae (x2), palatine (x2) and mandible
Define suture
Fibrous joints permitting little or no movement
T/F: the posterior fontanelle closes before the anterior fontanelle
t: anterior fontanelle after 18-24 monts, during first 2-3 months
What happens to the metopic suture
aka frontal suture, fuses.
3 sutures- between which bones
b/w frontal and parietal bones= coronal
b/w parietal bones= saggital suture
b/w parietal and occipital bones= lambdoid suture
State what the adult remains of the anterior and posterior fontanelle
AF- bregma
PF- lambda
used as landmarks in neurosurgery
Where are the lesser and greater wings of the sphenoid bone
lesser back of the orbit
greater on the side of the skull
Which bones lie superior and inferior to the greater wing of the sphenoid bone on the side of the skull
superior= frontal inferior= temporal
Which bone is found on the medial wall of the orbit
lacrimal bone
which bones can be found underneath the eye
zygomatic (lat), maxilla (medial)
What passes through the infraorbital foramen, and what bone is this foramen travelling through
Through the maxilla: the infraorbital nerve is a branch of the maxillary nerve, which is the 2nd branch of the trigeminal nerve (V2)- provides sensory innervation to cheek
Name of the protrusion in the maxilla in the midline
Anterior nasal spine
What nerve passes through the mental formamen
The mental nerve (a branch of the inferior alveolar nerve, which is a branch of the mandibular nerve which is a branch of the trigeminal nerve. Sensory innervation to the chin
Where is the vomer
In the midline back of the nose
Function and location of inferior nasal conchae
Turbinates- lamina of spongey bone projecting into nasal cavity to moisten and slow air as it enters
parts of the ethmoid bone?
orbital plate, middle nasal concha and perpendicular plate
The key landmark on the temporal bone?
external acoustic meatus
The zygomatic arch involves which 2 bones
zygoma and temporal
What is the cranial vault and what is it formed of
The space which actually contains the brain: occipital, temporal, frontal, parietal and the greater wings of the sphenoid
Where is the point of weakness within the skull and what is it called?
where 4 bones meet: frontal, temporal greater wing of sphenoid and parietal- called the pterion.
What runs behind the pterion?
Middle meningeal artery (can be ruptured if fracture –> extradural haematoma causing stroke
What is the occipitomastoid suture
Junction between occipital and mastoid process of the temporal bone
Which two bones are found in the top of the mouth. Which is more anterior
palatine bones (x2) and vomer. Palatine bones more anterior
What bone makes up the majority of the skull base
Occipital
Where does the vertetrae articulate with the base of the skull
Occipital chondyle
Where does the 7th cranial nerve emerge from the base of the skull
Stylomastoid foramen
What makes up the cranial base
Fossae (cavities): anterior, middle and posterior
What defines the posterior boundary of the anterior cranial fossa
Posteriorly and medially it is bounded by the limbus of the sphenoid bone. The limbus is a bony ridge that forms the anterior border of the prechiasmatic sulcus (a groove running between the right and left optic canals).
Posteriorly and laterally it is bounded by the lesser wings of the sphenoid bone (these are two triangular projections of bone that arise from the central sphenoid body).
What defines the posterior boundary of the middle cranial fossa
the superior border of the petrous part of the temporal bone (stony, solid part)
What bones make up the anterior cranial fossa
frontal, ethmoid and lesser wing of sphenoid
What part of the frontal bone is found in the anterior cranial fossa
orbital part
Name the raised, horizontal ridge on the ethmoid bone
Crista gali
Which structures of the ethmoid bone lie lateral to the crista gali- what are their significance
cribiform plate- they have foramina through which olfactory neurons pass up from the nose through the base of the skull to synapse onto the olfactory bulb which lies on the inferior side of the frontal lobes
Which bones make up the middle cranial fossa
greater wing of sphenoid, temporal and a bit of parietal
What part of the brain sits in the MCF
Temporal lobe
What is the sella turcica and what bone is it in
Bone housing the pituitary gland- held in the sphenoid bone (asa. hypophsial fossa)
State the foramina in the MCF
foramen spinosum and foramen ovale and foramen rotundum
What passes through the foramen spinosum
middle meningeal artery, middle meningeal vein, and the meningeal branch of the mandibular nerve
What passes through the foramen ovale
motor root of the trigeminal nerve (mandibular branch) and the accessory meningeal artery
What passes through foramen rotundum
maxillary branch of the trigeminal nerve
The clivus is part of what bone
Occipital bone
What happens in foramen magnum
Brainstem becomes continuous with spinal cord
Where does the oculomotor nerve emerge
between the 2 cerebral peduncles in the brainstem
Which cranial nerve emerges from the pons
trigeminal nerve
Which cranial nerve emerges most medially on the ponto-medullary junction
Abducent
Wha cranial nerve emerges lateral to the abducent on the pontomedullary junction
facial
Wha cranial nerve emerges lateral to the facial on the pontomedullary junction
vestibulocochlear
Pyramids are found on the dorsal surface of the brainstem t/f
F- they are on the anterior surface: they extend to the corticospinal tracts (from the ventral white matter of the spinal cord- carries voluntary motor fibres)
Where does the hypoglossal nerve emerge
b/w junction of pyramids and olives
State where each cranial nerve originates
midbrain: oculomotor (ant b/w peduncles) and trochlear (post)
Pons: trigeminal
pontomedullary junction: abducent, facial and vestibulocochlear (med–> lat)
medulla: glossopharyngeal, vagus and accessory
(spinal cord: b/w medulla and olive= hypoglossal)
Important foramina of anterior cranial fossa (or border with middle cranial fossa really)
optic canal (most anteriorly): optic nerve through back of orbit through orbit canal
Important foramina of medial cranial fossa in sphenoid bone
Superior orbital fissure-4 cranial nerves innervating extrinsic muscles of eye pass through, sympathetic fibres and ophthalmic veins
Foramen rotundum- maxillary nerve (V2)
Foramen ovale- mandibular nerve (V3) and accessory meningeal artery
Foramen spinosum- middle meningeal artery and vein and meningeal branch of mandibular nerve (V3)
Which structures (processes) surround the sella turcica and what is their function
clinoid processes (2 superior and inferior) which serve as attachment points for tentorium cerebelli
Foramina in the MCF in the temporal bone
Hiatus of the greater petrosal nerve – transmits the greater petrosal nerve (a branch of the facial nerve), and the petrosal branch of the middle meningeal artery.
Hiatus of the lesser petrosal nerve – transmits the lesser petrosal nerve (a branch of the glossopharyngeal nerve).
Carotid canal – located posteriorly and medially to the foramen ovale. This is traversed by the internal carotid artery, which ascends into the cranium to supply the brain with blood. The deep petrosal nerve also passes through this canal.
Foramina in the temporal bone in the PCF
internal acoustic meatus:in the posterior aspect of the petrous part of the temporal bone. It transmits the facial nerve (CN VII), vestibulocochlear nerve (CN VIII) and labyrinthine artery.
Foramina in the occiipital bone in the PCF
Foramen magnum- transmits the medulla of the brain, meninges, vertebral arteries, spinal accessory nerve (ascending), dural veins and anterior and posterior spinal arteries. Anteriorly an incline, known as the clivus, connects the foramen magnum with the dorsum sellae.
Jugular foramina: Located either side of the foramen magnum. Each transmits the glossopharyngeal nerve, vagus nerve, spinal accessory nerve (descending), internal jugular vein, inferior petrosal sinus, sigmoid sinus and meningeal branches of the ascending pharyngeal and occipital arteries
Hypoglossal canal: on anterolateral margin of foramen magnum, carries hypoglossal nerve
Blood supply to the meninges
From the middle meningeal artery, which is a branch of the maxillary artery, which is a branch of the external carotid artery (passes through foramen spinosum
State 2 layers of dura mater
periosteal and meningeal
Difference between dura mater in skull and vertebral canal
It is adherent to the skull but not to the vertebral canal due to spinal epidural space
Superior sagittal sinus drains where
through back of brain into the confluence of sinuses
Between which layers is the venous sinus formed
Periosteal and meningeal layer of the dura mater
Name of the dura that separates 2 hemispheres
falx cerebri
Name of dura separating cerebellum
falx cerebelli (so occipital lobe sits above the cranial fossa, above the tentorium, and cerebellum sits below)
What is the tentorial notch
Entrance to the posterior cranial fossa- above this you have cortices, below it you have cerebellum and brainstem
Where can brain tissue herniate?
underneath falx cerebri (subfalcine herniatin)
under the tentorium (transtentorial herniation= between brain and posterior cranial fossa- some of the temporal lobe can herniate)
tonsil of the cerebellum through the foramen magnum (tonsillar herniation)
Outline venous drainage of the brain
Superior sagittal sinus (superior border of falx) drains to confluence
Inferior sagittal sinus is inferior border of falx drains into straight sinus which drains into confluence
Great cerebral vein drains directily from brain into straight sinus
Transerse sinus –> sigmoid sinus –> internal jugular veins
Where does transverse sinus lie
below the falx cerebelli
Where does cavernous sinus lie
sitting on either side of the body of sphenoid bone in the cranial base. In middle cranial fossa
Which structures run through cavernous sinus
internal carotid arterires (abducent is assicated with this here), and also oculomotor, trochlear, opthalmic (V1) and maxillary (V2) run through the wall of the cavenous sinus.
