The Skull and Cranial Cavity Flashcards
How many bones is the skull formed from?
22 bones (plus ear ossicles)
How are most bones in the skull joined?
By sutures with the exception of the TMJs and the inner ear ossicle joints
How many pairs of synovial joints in the skull?
3
- temporomandibular
- 2 inner ear
Basic Facts of the Skull: Foramina:
- passageways
- vessels/nerves pass between the
cranial cavity and face/neck
Basic Facts of the Skull: Weight:
Reduced by the unique structure and paranasal sinuses
Bones in the upper dome of the skull are called calvaria and are unique containing
2 dense tables; external and internal which are separated by spongy bone called diploe
Bony Structure of the Skull:
What are the two divisions of the cranium and provide a brief description.
Neurocranium:
- contains brain and further divided
into
- Calvaria (upper domed part)
- Base (floor of cranial cavity)
Viscerocranium:
- contains viscera for sense organs
- lower anterior part; facial skeleton
Division of Cranium:
Neurocranium: What is the Calvaria formed from?
- paired temporal and parietal bones
- parts of unpaired:
- frontal bone
- occipital bone
- sphenoid bones
Neurocranium:
The base of cranium is formed from
parts of the sphenoid, ethmoid, temporal and occipital bones
Base of Cranium:
Skull Inferior View:
note there are medial and lateral pterygoid plates of sphenoid
Bones forming the Facial Skeleton:
- paired nasal bones
- lacrimal bones
- zygomatic bones
- inferior nasal conchae
- single ethmoid bone
- paired palatine bones
- unpaired vomer bone
Facial Skeleton:
not shown are the paired palatine and unpaired vomer
Facial Skeleton:
What skeleton is shown in this diagram? Label the diagram.
- facial skeleton in the inferior view
The hard palate is made from which bones?
Maxilla and palatine bones
Sutures and Junctions of the skull: Bregma:
Anterior junction of the sagittal suture with the coronal suture
Sutures and Junctions of the skull:
Sutures and Junctions of the skull: Lambda:
the posterior junction of the sagittal suture with the lambdoid suture is the lambda
occipital and parietal nerves
The mandible is part of the viscerocranium.
True or False?
True
Sutures and Junctions of the skull: Asterion:
the junction of the occipital, temporal and parietal bones
Sutures and Junctions of the skull: Pterion:
the junction of the temporal, parietal, frontal and sphenoid and is adjacent to the course of the middle meningeal artery
thinnest part of the skull
extradural haematome common here
Neonatal Differences:
- what are the —– gaps found in
foetus and neonate called?
- names
- closures
Landmarks of the Inferior Skull:
Clinical significance of the anterior fontanelle:
in newborn fontanelles allow brain expansion with growth
allow movement during labour
also allows evaluation of hydration status and intracranial pressure
Cranial Nerves:
- Olfactory – I
- Optic – II
- Oculomotor– III
- Trochlear – IV
- Trigeminal – V
- Ophthalmic V1, Maxillary V2 and Mandibular V3
- Abducens – VI
- Facial – VII
- Vestibulocochlear - VIII
- Glossopharyngeal – IX
- Vagus – X
- Accessory – XI
- Hypoglossal – XII
OOTTAFVGVAH
Floor of the Cranial Cavity:
- divisions
- first division with bones
- second division with bones
- third division with bones
- divided into 3 fossae
- anterior fossa: frontal, ethmoid, body and lesser wings of the sphenoid
- middle fossa: sphenoid, temporal
- posterior fossa: temporal and occipital with small contributions from sphenoid and parietal
Levels of fossae of cranial cavity floor:
anterior highest
posterior lowest?
Anterior Cranial Fossa:
- location (1)
- contains (2)
- bones (3)
- dural folds (2)
- nerves (?)
- above the nasal cavity
- contains the frontal lobes
- Orbital part of the front bone (thin)
- ethmoid bone separates from the
nasal cavity - lesser wings of sphenoid are
distinct boundary between anterior
and middle cranial fossa - Tentorium cerebelii attaches to
anterior clinoid processes = dural
folds - Falx cerebri attaches to the front
crest and crista galli (continous with
crest)
*Cribriform Plate of the ethmoid
bone is where the olfactory nerves
exit the skull
Anterior Cranial Fossa:
Middle Cranial Fossa:
- location
- consists of which bones (2)
- contains (3)
- dural folds (1)
- nerves
- below and behind anterior fossa
- sphenoid and temporal bones
- contains temporal lobes
- pituitary lies in sella turcica
- tentorium cerebelli attaches to
posterior clinoid processes - CN 2-6 exit the skull in the middle
cranial fossa
Middle Cranial Fossa:
- optic canal in middle cranial fossa in
lesser wing of sphenoid just posterior
to anterior clinoid process - CN2 = optic nerves exit the skull
Middle Cranial Fossa:
- superior orbital fissure
- CN3,4,5.1&6 and opthalmic veins exit
the skull here - Occhlomotor, Trochlear, Ophthalmic
branch of Trigeminal, Abducens
Middle Cranial Fossa:
- foramen rotundum
- cranial nerve 5.2
- maxillary branch of the
trigeminal nerve - passes to pterygopalatine fossa
Middle Cranial Fossa:
- CN 5.3
- mandibular nerve
- lesser petrosal nerve
- pass to the infratemporal fossa
Middle Cranial Fossa:
NO NERVES
Foramen Spinosum
Middle meningeall artery and veins
enter cranium from infratemporal fossa
Middle Cranial Fossa:
Foramen Lacerum
NO NERVES
- covered with cartilaginous plug
- no structures pass through
Middle Cranial Fossa:
- carotid canal
- internal carotid artery
- nerve plexus
Floor of the Cranial Cavity: Posterior Cranial Fossa:
- location
- size and depth
- bones
- contains
- lies behind and below middle
cranial fossa - largest and deepest cranial fossa
- parts of temporal and
occipital bones (tiny parts of
sphenoid and parietal) - contains brainstem and cerebellum
Posterior Cranial Fossa:
Posterior Cranial Fossa:
- CN7: Facial
- CN8: Vestibulocochlear
Posterior Cranial Fossa:
- jugular foramen
- CN 9,10,11
- Glossopharyngeal, Vagus, Accessory
- sigmoid sinus is continuous with
internal jugular vein - contains the inferior petrosal sinus
- the inferior petrosal sinus empties
into the internal jugular vein - memingeal branch of ascending
pharyngeal artery also passes
through the hypoglossal canal - medially the inferior petrosal sinus
leads to jugular foramen - laterally the sigmoid sinus leads to
the jugular foramen
Posterior Cranial Fossa:
- CN12: Hypoglossal nerve
Label parts of the plastic skull: Cranial Activity:
Label foramen: plastic skull:
insert
Label the optic canal and the superior orbital fissure
insert diagram
Label the optic canal and superior orbital fissure.
insert diagram
Label the foramen rotundum, foramen ovale, foramen spinosum, foramen lacerum and the carotid canal.
insert diagram
Label the internal acoustic meatus, jugular foramen and hypoglossal canal.
insert diagram
Skull Exterior Foramina
Paranasal Sinuses
Air sinuses are named by
the bone in which they are situated in
Paramedian view of Paranasal Sinuses:
Paranasal Sinuses:
- how many?
- what?
- function?
- sensory nerve supply?
- four paired paranasal air sinuses
- hollows within bones that form the
boundaries of the nose - communicate with the nasal cavity
via small apertures
(ostia) - contribute to warming and
humidifying inspired air - allows enlargement of certain areas
of the skull with minimal bone mass - lined with a respiratory mucous
membrane; secretes mucus moved
by cilia towards the ostium - reduce the weight of the skull
- sensory nerve supply by CNV; ostium
most sensitive, main sinus not
sensitive
What are the meninges?
- the meninges surround the brain
and spinal cord - cranial meinges continuous with
spinal meninges - 3 layers: Dura Mater, Arachnoid
Mater, Pia Mater
Meninges:
Dura Mater:
- divided into
- form
- 2 layers: outer periosteal, inner
meningeal - layers separate to form: dural
partitions and intracranial venous
structures; dural venous sinuses
Dura Mater
Dural partitions project into the cranial cavity and partially
subdivide the cranial cavity
Dural Partition: Falx Cerebri:
The falx cerebri is a crescent-shaped downward projection of meningeal dura mater from the dura lining the calva that passes between the two (right and left) cerebral hemispheres.
It is attached anteriorly to the crista galli of the ethmoid bone and frontal crest of the frontal bone.
Posteriorly it is attached to and blends with the tentorium cerebelli.
Dural Partitions: Tentorium Cerebelli:
The tentorium cerebelli is a horizontal projection of the meningeal dura mater that covers and separates the cerebellum in the posterior cranial fossa from the occipital lobe above.
It is attached posteriorly to the occipital bone along the grooves for the transverse sinuses.
Laterally, it is attached to the superior border of the petrous part of the temporal bone, ending anteriorly at the anterior and posterior clinoid processes.
The anterior and medial borders of the tentorium cerebelli are free, forming an oval opening in the midline (thetentorial notch), through which the midbrain passes.
Dural Partitions: Falx Cerebelli:
The falx cerebelli is a small midline projection of meningeal dura mater in the posterior cranial fossa. It is attached posteriorly to the internal occipital crest of the occipital bone and superiorly to the tentorium cerebelli. Its anterior edge is free and is between the two cerebellar hemispheres.
Dural Partitions: Diaphragma Sellae:
The final dural projection is the diaphragma sellae. This small horizontal shelf of meningeal dura mater covers the hypophyseal fossa in the sella turcica of the sphenoid bone. There is an opening in the center of the diaphragma sellae through which passes theinfundibulum, connecting the pituitary gland with the base of the brain, and any accompanying blood vessels.
Cranial nerves start from
the brain stem
travel through various foramen to exit the skull and cranial cavity
What separates the two layers of dura mater?
The outer periosteal and inner meningeal layer are separated by the dural venous sinuses
Clinical importance of tentorial notch:
tentorial notch is gap of dura where brainstem can herniate through
What is the main and largest artery supplying blood to the dura?
The middle meningeal artery:
- anterior meningeal arteries in the
anterior fossa
- middle and accessory meningeal
arteries in the middle fossa
- posterior meningeal artery in
posterior fossa
The anterior meningeal arteries are branches of
the ethmoidal arteries
The middle meningeal artery is a branch of
the maxillary artery
Which layer of dura does the meningeal arteries travel through? Enters the middle cranial fossa through?
- the outer periosteal layer
- foramen spinosum and divides into
anterior and posterior branches - the anterior branch passes almost
vertically to reach vertex of skull and
crosses pterion - the posterior branch passes in a
posterosuperior direction
The posterior meningeal artery is the terminal branch of?
the ascending pharyngeal artery and enters the posterior cranial fossa through the jugular foramen
A meningeal branch from the ——– artery arises as the ——— artery enters the posterior cranial fossa through the foramen magnum.
vertebral artery gives off a meningeal branch
enters through foramen magnum
The middle meningeal artery enters the middle cranial fossa through
the foramen spinosum, close to pterion where it is vulnerable to injury
Arterial Supply to the Dura:
**Venous Sinuses:
What is the venous sinus that joins the superior sagittal sinus to the inferior sagittal sinus?
The straight sinus (it is straight)
Ophthalmic vein drains the
infection can travel through ophthalmic vein into cavernous sinuses and result in cranial abscesses
Which venous sinus in known for infection spreading?
Cavernous sinuses
caverns, large and open
Coronal view of cavernous sinus:
**internal carotid artery sits within
the cavernous sinus (vein!!)
Cavernous Sinus Content:
Cavernous Sinuses are located
paired cavernous sinuses are against the lateral aspect of the sphenoid body bones on either side of the sella turcica
The Cavernous Sinuses receive blood from (3):
- cerebral veins
- ophthalmic veins
- emissary veins
Clinical importance of cavernous sinuses (2):
- allow infections to pass from
extracranial to intracranial - structures within are vulnerable to
injury from inflammation
What connects the right and left cavernous sinuses and where?
intercavernous sinuses on the anterior and posterior aspects of the pituitary stalk
Sphenoparietal sinuses:
- drain into
- location
- receive blood from
- drain into the anterior ends of each
of the cavernous sinuses - are small sinuses along the inferior
surface of the lesser wings of
sphenoid - receive blood from the
diploic and meningeal veins
Venous Drainage of the Cranial Cavity:
- cerebral, cerebellar, diploic and
emissary veins empty into dural
venous sinuses (scalp infection) - all venous sinuses eventually drain
into the internal jugular veins
**emissary veins can be a route for
infection as they have no valves
Venous Drainage of the Cranial Cavity:
insert diagram
Dural Nerve Supply:
Trigeminal nerve: V1
Dural Nerve Supply:
insert diagram
opthalmic upper, maxiallry, mandibular jaw
Arachnoid Mater:
- thin
- vascular
- enters longitudinal fissure
*subarachnoid space between arachnoid and pia; is location where CSF sits
*returns to circulation through
arachnoid granulations
Arachnoid Mater:
label and explain importance
insert diagram
arachnoid granulations are what CSF returns through from subarachnoid space into circulation
Pia Mater:
- follows every crevice of the brain
- thin
- invests surface of the brain
- surrounds roots of CN nerves at
origins
Extradural Haematomas are
arterial bleeds and occur quickly
Subdural Haematomas are
venous bleeds generally from where venous sinuses join the circulation
occur more slowly
Dural Partitions:
Which cranial nerves are pure sensory nerves?
I,II,VIII
(1,2,8)
(olfactory, optic, vestibulocochlear)
(OOV)
Which cranial nerves are pure motor nerves?
III,IV,VI,XI,XII
(3,4,6,11,12)
(occulomotor, trochlear, abducens, accessory spinal, hypoglossal)
(OTAAH)
Which cranial nerves are both motor and sensory nerves?
V,VII,IX,X
(5,7,9,10)
(trigeminal, facial, glossopharyngeal, vagus)
(TFGV)
