HS2-8 Cranial Cavity Flashcards
The cranial cavity is subdivided into what three cranial fossae?
anterior cranial fossa (anterior to lesser wing of sphenoid)
middle cranial fossa (lesser wing of sphenoid to petrous part of temporal bone)
posterior cranial fossa (posterior to petrous part of temporal bone)
What are the two layers of the cranial dura mater?
external layer (attached to bone)
internal layer (forms dural reflections)
What are the subdivisions of the cranial cavity formed by the dura mater?
falx cerebri
tentorium cerebelli
falx cerebelli
diaphragma sellae
What is the falx cerebri?
rigid partition between the cerebral hemispheres
What is the tentorium cerebelli?
rigid partition that separates posterior and middle cranial fossae
What is the falx cerebelli?
structure that partially separates the cerebellar hemispheres
What is the diaphragma sellae?
structure that forms roof over hypophyseal fossa
What structure is found between the two layers of dural reflections?
venous sinuses
What are the eight primary venous sinuses found in the cranial cavity?
superior sagittal
inferior sagittal
transverse
sigmoid
straight
superior petrosal
inferior petrosal
cavernous
The sigmoid sinuses drain into
the internal jugular veins
The inferior petrosal sinuses drain
the cavernous sinus into the jugular foramen
Label the following diagram.
How is the subarachnoid space of the cranial cavity continuous with the subarachnoid space of the spinal cord?
continuous via foramen magnum
Where is CSF formed in the cranial cavity?
formed in choroid plexuses of lateral, 3rd, and 4th ventricles of brain
Describe the relationship between CSF and arachnoid granulations.
CSF is partially absorbed by arachnoid granulations in dural sinuses, especially superior sagittal sinus
Nearly all venous drainage from the brain is conducted through the dural venous sinuses into the internal jugular vein. What are three collateral pathways of venous drainage from the brain?
ophthalmic veins (cavernous sinus to orbit to facial vein)
unnamed veins (cavernous sinus to pterygoid plexus to deep facial vein)
emissary veins (dural sinuses to diploë of cranial roof)
How do the vertebral arteries enter the cranial cavity?
enter posterior cranial fossa through foramen magnum
What happens to the vertebral arteries after they enter the cranial cavity via the posterior cranial fossa/foramen magnum?
vertebral arteries join to form basilar artery
How do the internal carotid arteries enter the cranial cavity?
enter via carotid canal
What do the internal carotid arteries do after entering the cranial cavity?
gives off branches that contribute to the cerebral arterial circle
What are the three cerebral arteries that provide the blood supply to the cortex and deeper parts of the cerebrum?
anterior cerebral artery
middle cerebral artery
posterior cerebral artery
What is the primary arterial supply to the meninges?
middle meningeal artery
The middle meningeal artery is a branch of
the maxillary artery
How does the middle meningeal artery enter the cranial cavity?
enters middle cranial fossa through foramen spinosum
Describe the volume composition of the cranial cavity.
brain tissue + interstitial fluid = 80%
CSF = 10%
vascular compartment = 10%
What is a secondary brain injury?
movement of brain within cranial cavity that leads to tearing/rupture of blood vessels
List three types of secondary brain injuries.
epidural bleeding
subdural bleeding
subarachnoid bleeding
What is epidural bleeding?
bleeding between bone of skull and outer layer of dura
What causes epidural bleeding?
rupture of meningeal artery, often the middle meningeal artery at pterion
What is subdural bleeding?
bleeding between inner layer of dura and arachnoid
What causes subdural bleeding?
rupture of bridging vein, which connects cerebral vein with dural sinus
What is subarachnoid bleeding?
bleeding into the subarachnoid space
What causes subarachnoid bleeding?
rupture of branch of a cerebral artery
What is the relationship between the size of the vasculature of the brain and brain injuries?
increase in size of brain vasculature will set up pressure gradients within cranial cavity that can shift brain tissue
What are four general features of secondary brain injuries?
damage occurs some time after primary injury
symptoms due to reduced brain and nerve activity
symptoms develop gradually
damage is treatable and reversible
What are four specific features of secondary brain injuries?
gradual changes in behavior
severe headache
changes in respiration/BP/HR
changes in cranial nerve function
What happens in a tentorial herniation?
oculomotor nerve is pressed against tentorial incisure
What is the result of a tentorial herniation? (3)
results in:
dilation of pupil on same side
ptosis (drooping) of eyelid on same side
eyeball turned laterally
What is the primary difference between the dura mater found in the cranial cavity and the dura mater found in the spinal cord?
dura mater in cranial cavity has two layers
Between which layers of the meninges is CSF found?
between arachnoid mater and pia mater
What are the two layers of the dural reflections?
periosteal
meningeal
Draw a diagram of venous sinus flow in the cranial cavity.
Vertebral arteries are a branch of
the subclavian artery
The anterior and middle cerebral arteries are derived from
the internal carotid artery
The posterior cerebral artery is derived from the
basilar artery
A rupture of the middle meningeal artery eventually results in
an epidural hematoma
