Session 1: Cranium, Meninges and Brain Flashcards
What is another name for the facial skeleton?
Visceroskeleton
What are the main components of the visceroskeleton? How many bones make it up?
Made of 22 bones (excluding ossicles of the ears)
Main components:
Cranium (Vault + Base)
Facial skeleton (Viscerocranium)
Mandible
What are the two parts of the cranium?
Vault and Base
Name all the cranial bones.
Frontal
Parietal x 2
Temporal x 2
Occipital
Sphenoid
Ethmoid
Name all the facial bones.
Mandible
Maxillary
Zygomatic
Nasal
Lacrimal
Inferior Nasal Concha
Vomer
Palatine
What are the gaps between the bones in the skull during development called? Identify between which bones they are and when they close.
What is the name of the suture that seperated the frontal bone present in babies?
Fontanelles
anterior fontanelle - frontal & parietal bones (18-24 months)
posterior fontanelle- parietal and occipital bones (2-3 months)
Frontal suture (Meitopic suture)
What is the role of the nasal conchae? What cranial bone are the superior nasal concha and middle nasal concha derived from?
Increase the surface area of the upper respiratory tract
Derived from the ethmoid bone
N.B. Inferior nasal concha is a facial bone.
Give an example of a synovial joint within the skull.
Temporo-mandibular Joint
What are the tough fibrous joints between bones in the skull called?
Sutures
Give the names of the sutures between:
a) frontal and parietal bones
b) parietal bones
c) parietal and occipital bone
Coronal Suture
Sagittal Suture
Lambdoid Suture
What is the name given to the point at which the sagittal suture meets the coronal suture?
Bregma
What is the name given to the point at which the sagittal suture meets the lambdoid suture?
Lambda
List the three folds of dura mater in the cranium and describe their location.
Falx cerebri - along the fissure between the two cerebral hemispheres
Falx cerebelli - between the two cerebellar hemispheres (seperates them)
Tentorium cerebelli - between cerebellum (seperates them) & occipital lobes
How can the cranial base be divided?
Name the relations to the brain regions and skull bones
Divided by Cranial Fossae:
Anterior Cranial Fossa - frontal lobes (frontal, ethmoid + sphenoid bones)
Middle Cranial Fossa - temporal lobes ( temporal + sphenoid bones)
Posterior Cranial Fossa - cerebellum (temporal + occipital bones)
What are the three layers of the meninges?
Dura mater (Periosteal and meningeal)
Arachnoid mater
Pia mater
What are the two layers of dura in the cranium?
Periosteal (outer layer) and Meningeal (inner layer)
Which layer of the meninges goes in and out of the sulci?
Pia Mater
What difference between the cranial dura and spinal dura allows for an epidural space?
At the foramen magnum the dura goes from having two layers (periosteal and meningeal) to just one layer (equivalent of the meningeal layer). This means that there is an epidural space sorrounding the spinal cord.
How is CSF drained into circulation?
CSF drains into dural venous sinuses via the arachnoid granulation villi
Describe the arrangement of dural venous sinuses and the direction of blood flow.
How many veinous sinuses and where are they located?
11 dural venous sinuses, located between the periosteal and meningeal layers of the dura mater.
Superior sagittal sinus - located along the top of falx cerebri
Inferior sagittal sinus - along bottom of falx cerebri
The inferior sagittal sinus and great cerebral vein of Galen drain into straight sinus.
The straight sinus + superior sagittal + occipital sinus all drain into the confluence
Confluence drain through right and left transverse sinuses into to right and left sigmoid sinuses which drain into right and left internal jugular veins
Cavernous sinuses (R&L) drain into superior petrosal sinuses (both right and left) which drain into the sigmoid sinuses.
Cavernous sinuses can also drain into inferior petrosal sinuses which drain directly into the internal jugular veins.
Cavernous sinuses drain from right and left pterygoid plexi, superior and inferior ophthalmic veins. Anterior and posterior intracavernous sinuses connect right and left cavernous sinuses
What flat sheet of dura (with a small hole in it) keeps the pituitary gland in the sella turcica?
Diaphragma sellae
List three different types of brain herniation and their consequences.
Subfalcine herniation – cingulate gyrus [The gyrus sorounding the corpus callosum (of frontal lobe) goes under falx cerebri
Uncal/transtentorial/uncinate – inner part of temporal lobe (uncus) goes under tentorium cerebelli. This affects the midbrain and can cause pupil/vision problems and unconsciousness
Tonsilar herniation – cerebellar tonsils go through foramen magnum. This can affect medulla and cause cardiorespiratory failure
Which two main vessels supply the circle of Willis?
Vertebral arteries and internal carotid arteries
There is a weak point in the skull behind which you find the largest artery entering the skull. Name the part of the skull in question and the artery. Explain the clinical significance of this
Pterion: Region where the frontal, parietal, sphenoid and temporal bones meet.
Behind this area of the skull you find the middle meningeal artery.
Therefore if there is trauma to the pterion, it may result in rupturing of the middle meningeal artery and cause an extradural haemorrhage.
What are emissary veins and what is their clinical relevance?
Drain blood from scalp (outside of skull) into superior sagittal sinus via parietal foramina.
Provide an entry route for infections to enter intracranial space
Which veins drain into the cavernous sinus?
Superior and inferior ophthalmic veins
There is also communication with the pterygoid plexus
What is the pterygoid plexus and where is it located?
A venous plexus of considerable size
Is situated between the temporalis muscle and lateral pterygoid muscle, and partly between the two pterygoid muscles
Name three structures found within the cavernous sinus.
Internal carotid artery
Various cranial nerves (occulomotor, trochlear, trigeminal [ophthalmic and maxillary divisions] and abducens)
Pituitary Gland
What are the different tissue layers of the scalp? What is the clinical importance of a laceration there?
Skin
Connective Tissue
Aponeurosis
Loose Areolar Tissue
Periosteum (vascular connective tissue enveloping all bones)
Laceration to the heavily perfused scalp (by external carotid + ophthalmic branches) will lead to profuse haemorrhage due to the dense connective tissue keeping the cut vessels open
What is the tentorial notch and what is its clinical significance?
Triangular opening in the tentorium cerebelli through which the brainstem extends downwards
Increased intracranial pressure can cause part of the temporal lobe to be pushed through this opening, this is known as a uncal/temporal herniation.
Which major arteries pass through the foramen magnum?
Vertebral arteries
List all the cranial foramina
Cribriform plate
Optic canal
Superior orbital fissure
Foramen rotundum
Foramen ovale
Foramen spinosum
Foramen lacerum
Internal Acoustic Meatus
Jugular Foramen
Hypoglossal Canal
List the three branches of the trigeminal nerve and the foramina through which they pass
Ophthalmic – Superior Orbital Fissure
Maxillary – Foramen Rotundum
Mandibular – Foramen Ovale
Which artery passes through the optic canal?
Ophthalmic Artery
Which vessels passes through the superior orbital fissure?
Superior Ophthalmic Vein
Inferior Ophthalmic Vein
Which foramen does the internal carotid artery pass through?
Carotid Canal
Which vessel passes through the internal acoustic meatus?
Labyrinthine Artery
Which foramen do the spinal roots of the accessory nerve pass through?
Foramen Magnum
Besides the emissary veins, name another vein that can provide entry for infections from the outside into the cranium
Facial vein connects with the cavernous sinus
