Cranial Cavity Flashcards
What are the membranes inside the skull surrounding the brain?
3 meninges:
- Dura mater
- Arachnoid mater
- Pia mater
Describe the dura
Outer layer
Tough
Fibrous
Attaches to internal aspect of skull
Describe the arachnoid
Intermediate layer
Lines inner surface of dura
More delicate
Still fibrous
Describe the pia
Innermost layer
Attached to brain
Very difficult to separate from brain
What is the extradural space?
Potential space between skull and dura
Where does blood collect when the meningeal arteries rupture?
In extradural space
What is the subdural space?
Potential space between dura and arachnoid
Where does blood collect with venous bleeding?
In subdural space
What is the subarachnoid space?
Real space between arachnoid and pia
Filled with CSF
Is there anything between the pia and the brain?
No
What are the dural septa?
Dural partitions that project into cranial cavity
Leaves skull
Lodge in between subdivisions of brain
Stop rotational displacement
Describe the falx cerebri
Sickle/comma shaped
Lies in midline directly beneath sagittal suture
Partway between two cerebral hemispheres
Free inferior edge
Upper margin attached to skull in midline
Goes posteriorly as far as internal occipital protuberance
Anteriorly plugs into cristagalli of ethmoid bone
In sagittal plane
Describe the tentorium cerebelli
Tented Crescent shaped In horizontal plane From posterior aspect of skull Forms roof for posterior cranial fossa Lodges between cerebral hemispheres above and cerebellum below Attached edge posteriorly Free edge anteriorly
Describe the falx cerebelli
Small
Comes in posteroinferiorly
Lodges between cerebellar hemispheres
Describe the diaphragma sellae
Roof to sella turcica
What is the sella turcica?
Small depression in sphenoid bone where pituitary gland sits
Describe the structure of the dura
Like two layers - Outer = periosteal - Inner = meningeal For most part stuck together Where septa form - Outer layer continues to line skull - Inner layer comes down in two places forming double fold
What is the dural venous sinus?
Venous pool in little space formed by two layers of dura coming away
Describe the dural venous sinus
Endothelial lined space Between outer an inner layer of dura Filled with venous blood Receives blood from - Brain via cerebral veins - Spongy bone of skull via diploid veins - Scalp via emissary veins
How can infection from the scalp spread into the brain and meninges?
Venous blood from scalp carrying infection drains into dural venous sinuses
Describe the superior sagittal venous sinus
At superior margin of falx cerebri
Gets larger as it extends from anterior to posterior aspect of falx cerebri
Describe the inferior sagittal sinus
In inferior aspect of falx cerebri
Between double fold
Where does the falx cerebri attach to the tentorium cerebelli?
At inferior margin
Two septa at right angles to each other
Describe the straight sinus
Where falx cerebri and tentorium cerebelli join
Here, inferior sagittal sinus straightens out into straight sinus
Runs towards superior sagittal sinus
Where do the superior sagittal sinus and the straight sinus meet?
Confluence of sinuses
At internal occipital protuberance
Describe the transverse sinuses
Blood goes either left or right at confluence of sinuses
Moves in root of tentorium cerebelli
Heads all the way around to step between middle and posterior cranial fossae at petrous part of temporal bone
Describe the sigmoid sinus
Transverse sinus S-shapes down to jugular foramen and beginning of internal jugular vein
Describe the petrosal sinus
Small sinus related to petrous part of temporal bone
Describe the cavernous sinus
Either side of body of sphenoid
In split in dura over sphenoid
Major structures move through them
What arteries supply the bones and meninges?
Many small meningeal arteries
What is the largest and most important meningeal artery?
Middle meningeal artery
What artery is the middle meningeal artery of?
Maxillary artery
What foramen does the middle meningeal artery go through to reach the inside of the skull?
Foramen spinosum
What are the two branches of the middle meningeal artery?
Anterior
Posterior
Which artery grooves the interior aspect of the pterion?
Anterior branch of the middle meningeal artery
Where are the meningeal arteries located?
In extradural space
Between dura and skull in little grooves in bone
Why is it a medical emergency when a meningeal artery is torn?
Thin flat bone of skull fractures > makes sharp spikes > tears artery > blood in extradural space Blood collects Raises ICP Herniation and compression of brain stem Depression of respiratory centres Respiratory arrest
How do you fix the raised ICP when due to an extradural haematoma?
Drill hole in skull
What is the cla suck subdural haemorrhage?
Person falls
Tear at point where cerebral veins enter superior sagittal sinus
Slow ooze of venous blood into subdural space
Is it possible for a subdural haemorrhage to never present?
Yes
Sometimes found on autopsy
Sometimes calcifies and pits > forms epileptic focus
