Skull and Intracranial Region Flashcards
What are the 2 parts of the cranium?
- Neurocranium
- Viscerocranium
What does the neurocranium consist of?
Skull cap (calcaria). Cranial base (basicranium) Intracranial region (inner surface skull base).
What does the viscerocranium consist of?
Facial bones in anterior cranium.
How many bones form the neurocranium?
8
Which bones form the neurocranium?
Singular bones: - frontal, ethmoidal, sphenoidal, occipital.
Paired bones: - temporal, parietal.
Which bones form the viscerocranium?
Singular bones: - mandible, vomer.
Paired bones: - maxillae, inferior nasal conchae, zygomatic, palatine, nasal, lacrimal.
List the cranial bones.
Frontal Parietal Occipital Temporal Sphenoid Ethmoid
List the facial bones.
Maxilla Palatine Zygomatic Lacrimal Nasal Vomer Inferior nasal conchae Mandible
What forms the nasal septum?
Ethmoid + Vomer
What shape is the sphenoid bone?
Butterfly
What suture fuses the frontal bone and parietal bones?
Coronal suture
What suture fuses the 2 parietal bones?
Sagittal suture
What suture fuses the parietal bones and the occipital bone?
Lambdoidal suture
What suture fuses the parietal bone and the temporal bone?
Squamous suture
Why is the inner surface of parietal bones concave and grooved?
To accommodate the brain and blood vessels
What does the sphenoid bone articulate with?
Unpaired bones – Occipital, vomer, ethmoid and frontal bones.
Paired bones – Temporal, parietal, zygomatic and palatine bones.
Where is the cribiform plate found?
On the ethmoid bone.
What is the purpose of the inferior nasal conchae?
Create turbulence of inhaled air
What are the 4 processes of the maxilla?
- Zygomatic process
- Frontal process
- Horizontal palatine process
- Curved alveolar process
What bones form the bridge of the nose?
Nasal bones
Which bones are more commonly fractured?
Nasal bones
What is the lambda?
Where the lambdoidal and sagittal suture meet
What is the bregma?
Where the coronal and sagittal suture meet
What structures pass through the foramen magnum?
- Medulla oblongata
- Meninges
- Vertebral arteries
- Anterior and posterior spinal arteries
- Dural veins
- Spinal division of accessory nerve (ascends through foramen magnum to join cranial division which then exits through jugular foramen)
What are the 4 skull air sinuses?
- Frontal
- Sphenoid
- Maxillary
- Ethmoid
What are sutures?
Fibrous joints (synarthroses) between bones of skull. They ossify with age and become less mobile.
What are the purpose of sutures?
Allow bones to move during birth.
Allows bone to enlarge evenly as brain grows and skull expansionists to result in symmetrically-shaped head.
What are Wormian bones?
New bones created by sutures.
Where does the cranial base articulate with the cervical spine?
Occipital condyle
Which head movements does the cervical spine allow?
- Flexion: - forwards.
- Extension: - backwards.
- Lateral flexion: - bend side-to-side.
- Rotation: - turn side-to-side
In the cervical spine, which foramen does the vertebral artery run through?
Transverse foramen
What are the 3 cranial fossa?
Anterior, Middle and Posterior
What makes up the Anterior Cranial Fossa?
- Frontal bone
- Ethmoid bone
- Lesser wing of sphenoid bone
What makes up the Middle Cranial Fossa?
- Rest of sphenoid bone (greater wings, body and sinus)
- Petrous part of temporal bone
What makes up the Posterior Cranial Fossa?
- Temporal bone (rest of it)
- Occipital bone
What is the sella turcica?
Saddle-like prominence that crosses the midline on the superior surface of the body of the sphenoid.
Where is the pituitary gland located?
In the hypophyseal fossa of the sella turcica.
What passes through the foramen lacerum?
Internal carotid artery crosses it
What passes through the foramen spinosum?
Middle meningeal artery
What passes through the internal acoustic meatus?
Facial nerve (CN VII) Vestibule-Cochlear (CN VIII) Labyrinthine artery
What passes through the carotid canal?
Internal carotid artery
What sinuses pass through the jugular foramen?
Inferior petrosal and sigmoid sinuses
What could be the reason of facial asymmetry?
Craniosynostosis - sutures fusing prematurely.
What other structures may be damaged by a skull fracture?
Membranes, blood vessels, brain.
What does the middle meningeal artery supply?
Meninges and Calvaria.
What is the middle meningeal artery a branch of?
Branches off the maxillary artery which is a terminal branch of the external carotid artery.
What are the 3 meningeal partitions?
Falx cerebri
Falx cerebelli
Tentorium cerebelli
What is the Falx cerebri?
Fold of dura mater within the longitudinal fissure that separates the 2 brain hemispheres.
What is the Falx cerebelli?
Fold of dura mater separating the cerebellar hemisphere.
What is the Tentorium cerebelli?
Extension of dura mater, separating the cerebellum from the inferior region of occipital lobes.
Where are the dural venous sinuses located?
Between periosteal and meningeal layers of dura mater.
What do the dural venous sinuses contain?
Venous blood
Dural venous sinuses do not contain valves. What can be the impact of this?
Infection can easily spread from the face to areas of the intracranial cavity.
How does blood leave the cranial cavity?
Blood from dural venous sinuses drain via internal jugular vein.
Flows through brachiocephalic vein and superior vena cava to reach right atrium of heart.
What are the names of the 8 dural venous sinuses?
- Superior sagittal sinus
- Inferior sagittal sinus
- Straight sinus
- Cavernous
- Superior petrosal
- Inferior petrosal
- Transverse sinus
- Sigmoid sinus
Where is the cavernous sinus located?
Posterior to maxillary sinuses and lateral to the pituitary (above sphenoid bone).
It is bordered by the temporal and sphenoid bone.
What is the circle of Willis?
Circle of arteries that supply blood to the brain and surrounding structures.
If one becomes blocked/narrows, blood can still be supplied via collaterals.
What is the circle of Willis composed of?
- Anterior and posterior communicating artery.
- Internal carotid artery - gives off anterior and middle cerebral arteries.
- Posterior cerebral artery.
- Vertebral artery (from spine) - forms basilar artery at level of pons.
What structures pass through the cavernous sinus?
- CN III (oculomotor)
- CN IV (trochlear)
- CN V1 (ophthalmic of trigeminal)
- CN V2 (maxillary of trigeminal)
- CN VI (abducens)
- Internal carotid artery (and sympathetic nerve fibres on the carotid)
What is the cisterns magna?
Subarachnoid space
What does the falx cerebri contain along the line of the sagittal suture?
- Superior sagittal sinus (contained in upper margin of falx cerebri and overlies the longitudinal fissure of the brain)
- Inferior sagittal sinus (contained in inferior margin of falx cerebri and arches of the corpus callosum).
What is the function of the crista galli?
Place of attachment for falx cerebri.
What lies on the cribriform plate?
Olfactory bulb
Which bone does the trigeminal ganglion sit on?
Near apex of petrous part of temporal bone.
Why does the trigeminal ganglion not contain synapses?
Nerves just travel through it.
In which fossa does the cerebellum lie?
Posterior cranial fossa.
Through which foramen do the major blood vessels supplying the brain enter the cranium?
Foramen magnum - vertebral arteries.
Carotid canal - Internal carotid artery.
