Week 7: Cranial Cavity and Contents Flashcards
Cranial fossae
- floor of cranial cavity divided into 3 distinct fossae
* anterior, middle, posterior
anterior cranial fossa
- most shallow
- forms roof of orbits
- lies superior to nasal cavities
- accommodates and supports frontal lobes of brain
primary foramen of anterior cranial fossa
- cribiform plate
* supports olfactory bulbs of first cranial nerve (CN I)
middle cranial fossa
- located centrally
* accommodates temporal lobes and pituitary gland
Foramina of middle cranial fossa
carotid canal, optic canal, superior orbital fissue, foramen rotundum, foramen ovale, and foramen spinosum
posterior cranial fossa
- most posterior and deepest
* accommodates brainstem and cerebellum
Foramina of posterior cranial fossa
internal acoustic meatus, jugular foramen, hypoglossal cana, and foramen magnum
What passes through superior orbital fissure
•in middle fossa •oculomotor nerve (CN III) •trochlear nerve (CN IV) •opthalmic nerve (V1) Abducens nerve (CN VI)
What passes through optic canal?
- in middle fossa
- optic nerve (CN II)
- ophthalmic artery
what passes through foramen rotundum?
- in middle fossa
* maxillary nerve (V2)
What passes through foramen ovale?
- in middle fossa
* mandibular nerve (V3)
What passes through carotid canal?
- in middle fossa
- internal carotid artery
- internal carotid nervous plexus (sympathetic)
What passes through foramen spinosum?
- in middle fossa
* middle meningeal artery
What passes through internal acoustic meatus?
- in posterior fossa
- facial nerve (CN VII)
- vestibulocochlear nerve (CN VIII)
What passes through jugular foramen?
- in posterior fossa
- sigmoid sinus
- glossopharyngeal nerve (CN IX)
- vagus nerve (CN X)
- accessory nerve (CN XI)
What passes through hypoglossal canal?
- in posterior fossa
* hypoglossal nerve (CN XII)
What passes through foramen magmum?
- in posterior fossa
- vertebral arteries
- accessory nerve (spinal contribution fo CN XI)
- anterior and posterior spinal arteries
dura mater
- outermost of meninges
* 2 layers: outer periosteal layer and inner meningeal layer
subarachnoid space
- between arachnoid mater and pia mater
* contains CSF
name the dural venous sinuses
- superior and inferior sagittal sinuses
- straight sinus
- confluence of sinuses
- transverse
- sigmoid
- cavernous sinus
dural venous sinuses function
drain blood from the brain and eventually empty into the internal jugular veins
what are dural venous sinuses?
- periosteal and meningeal layers of dura separate to form several endothelial lines venous structures that include
- contained within the reflections of the dura that separate the various brain regions and lobes
falx cerebri
- reflection found between 2 cerebral hemispheres
* contains superior and inferior sagittal sinuses and straight sinus
tentorium cerebelli
- fold of dura that covers the cerebellum and supports occipital lobes
- contains transverse sinuses
falx cerebelli
- dura between 2 cerebellar hemispheres and diaphragma sellae
- covers sells turcica and pituitary gland
- contains cavernous sinus
arachnoid granulations
small projections of arachnoid that extend into the dural sinuses and empty or recycle CSF into venous system
bridging veins
- drain blood from brain
- pass through subarachnoid space and dura
- empty into dural venous sinuses
cause of epidural hematoma
- usually results from skull fracture, which may cause laceration of vessels
- in children, temporary displacement of skull bones can lead to laceration without fracturing skull
most common place for skull fracture
- region of temporal bone
* tremendous force usually required
symptoms of epidural hematoma
- usually brief LOC followed by lucid interval lasting minutes to hours
- usually followed by HA, progressive alteration of consciousness, and weakness (hemiparesis)
what does epidural look like on CT?
convex, lens-shaped hyperdensity that may cross midline
cause of subdural hematoma
- head trauma that causes rupture of bridging veins
* displacement of brain can cause tearing at the point where bridging veins penetrate the dura
why are bridging veins susceptible to rupture?
the brain floats freely in CSF, but venous sinuses (to which bridging veins attach) are fixed
who are especially susceptible to subdural hematoma?
•elderly and alcoholic -> brain atrophy -> bridging veins are stretched and brain has more space for movement •only need minor head trauma for subdural hematoma
symptoms of subdural hematoma
HA and AMS without other clinical signs
what does subdural hematoma look like on CT?
crescent-shaped concave hyperdensity that follows contours of brain and does not cross midline
subarachnoid hemorrhage
a life-threatening type of stroke caused by bleeding into subarachnoid space, which may be caused by an aneurysm, arteriovenous malformation, or TBI
what is an arteriovenous malformation
- abnormal tangle of arteries and veins with no capillaries in between that rupture and bleed
- can be a cause of subarachnoid hemorrhage
Symptoms of subarachnoid hemorrhage
sudden onset of severe HA, often described as “worst HA of my life” with nausea, vomiting, neck or back pain, dizziness, and possible sz
What does subarachnoid hemorrhage look like on CT?
- vary depending on vessel that is bleeding
* LP with blood in CSF is also confirmatory
blood supply to brain and spinal cord
provided primarily by branches of paired internal carotid and vertebral arteries
circle of willis
- anastamosis in the cranial cavity of the paired internal carotid and vertebral arteries
- supplies the cerebrum
3 cerebral arteries that branch off circle of willis
anterior, middle, and posterior
anterior cerebral arteries supply
anterormedial portion of cerebrum
middle cerebral arteries supply
majority of lateral brain
posterior cerebral arteries supply
both medial and lateral parts of the posterior cerebrum
brainstem and spinal cord primarily supplied by
branches of the vertebral artery and branches of the aorta
anterior spinal artery
- arises from vertebral artery
* its branches supply anterior 2/3 of spinal cord
posterior spinal artery
- arises from either vertebral artery or basilar artery
* supplies posterior 1/3 of spinal cord
segmental arteries
- branches of posterior intercostal and lumbar arteries from the aorta
- anastamose with the anterior and posterior spinal arteries
where is CSF produces
ependymal cells of choroid plexus
what absorbs CSF
arachnoid villi
where is CSF drained
to superior sagittal sinus then to venous system
sagittal dural sinus
receives CSF
cavernous dural sinus
- between temporal and sphenoid bones
* contains many nerves and internal carotid
cavernous sinus syndrome
- caused by compression of cavernous dural sinus
- HA, swollen eyes, impairment of occular motor nerves, Horner’s syndome, sensory loss 1st/2nd divisions trigenimal nerve
