Cranial cavity Flashcards
What are the 3 cranial fossae ?
- anterior cranial fossa
- middle cranial fossa
- posterior cranial fossa
Describe the bones and contents of the anterior cranial fossa
- smallest and shallowest cranial fossa
- made up of the frontal bone, ethmoid bone and sphenoid bone
- contains the frontal lobe of the brain
Describe the bones and contents of the middle cranial fossa
- made up of the sphenoid bone and temporal bone
- contains the temporal lobe and pituitary gland
Describe the bones and contents of the posterior cranial fossa
- it is the deepest and largest fossa
- made up of the occipital bone and a little bit of the sphenoid and temporal bone
- contains the cerebellum and brainstem
What are the 3 meninges of the brain ?
- the meninges are the surrounding layers of the brain
- outermost layer = dura mater
- middle layer = arachnoid mater
- innermost layer = pia mater
Describe the dura mater of the brain
- tough parchment like
- double layer : inner meningeal layer and outer periosteal layer
Describe the arachnoid mater of the brain
- very thin
- avascular
- lies above the subarachnoid space which contains the cerebrospinal fluid
Describe the pia mater of the brain
- thin
- adherent to the brain surface
- enters the contours on the surface of the brain
What is the difference between the dura mater of the of the brain and the spinal cord ?
- the cranial dura mater has 2 layers whereas the spinal dura mater has 1 layer
- the meningeal layer of the cranial dura mater descends down to the vertebra and becomes spinal dura mater
What forms when the 2 layers of the cranial dura separate ?
- dural venous sinuses
- dural partitions
What is a dural venous sinus ?
- the space between the 2 layers of cranial dura mater when they separate
- filled with venous blood
What is a dural partition ?
When the meningeal layer of the dura mater invaginates between regions of the brain
What happens of damage occurs to the middle meningeal artery ?
- the middle meningeal artery lies deep to the pterion
- if the artery is damaged then an extradural haematoma will occur
- this is when blood fills between the skull periosteum and dura mater
List the dural partitions
- falx cerebri
- tentorium cerebelli
- falx cerebelli
- tentorial notch
- diaphragma sellae
- infundibulum of hypophysis cerebri
What is the diaphragma sellae ?
It is a sheet of dura mater that forms the roof of the pituitary fossa
Describe the position of the falx cereberi
- it is sickle shaped
- separates the right an left hemispheres of the cerebrum
Describe the position of the tentorium cerebelli
- lies transversely
- superior to the cerebellum
- lies between the occipital lobe and cerebellum
Describe the position of the falx cerebelli
- lies below the tentorium cerebelli
- found between the left and right hemispheres of the cerebellum
Describe the tentorial notch
- it has a sharp edge
- found on the medial margin of the tentorium cerebelli
Describe the supply and drainage of the dural venous sinuses
- dural venous sinuses receive blood from diploic veins and emissary veins
- blood from the dural venous sinuses drain into the internal jugular veins
- venous blood of the brain drains into dural venous sinuses
What is meningitis ?
If infection is present in the dural venous sinuses this can lead to inflammation of the meninges - meningitis
Describe the structure of the bone of the skull
- flat bone
- the outer and inner tables are made from compact bone
- the area between the tables is bone marrow and spongy bones and it is known as diploe
List the dural venous sinuses
- superior sagittal sinus
- inferior sagittal sinus
- straight sinus
- transverse sinus
- sigmoid sinus
- inferior petrosal sinus
- superior petrosal sinus
- cavernous sinus
- sphenoparietal sinus
What is the confluence of sinuses ?
The point at which the superior sagittal sinus, straight sinus and transverse sinus meets
Describe the location of the superior sagittal sinus
It is found on the superior border of the falx cereberi
Describe the location of the inferior sagittal sinus
It is found on the inferior border of the falx cereberi
Describe the location of the straight sinus
It connects the inferior sagittal sinus and confluence of sinuses
Where does the sigmoid sinus leave the cranial cavity ?
It leaves via the jugular foramen
Describe the location of the superior petrosal sinus
It is found on the upper border of the petrous part of the temporal bone
Describe the location of the cavernous sinus
It is found on the lateral border of the sellae turcica
Describe the location of the sphenoparietal sinus
It is found along the edge of the lesser wing of the sphenoid bone
What is the great cereberal vein ?
- it unites with the inferior sagittal sinus to form the straight sinus
- it drains venous blood from the brain
What are arachnoid granulations ?
protrusions of the arachnoid mater which allow CSF to enter dural venous sinuses
What are the trabeculae of the arachnoid mater ?
Delicate strands of connective tissue that connect the arachnoid mater and pia mater
What is the subarachnoid space ?
- filled with CSF
- contains blood vessels
- found beneath the arachnoid mater
Which osteological feature of the occipital bone articulates with the superior articular facet of the atlas ?
occipital condyles
What is the difference between a venous sinus and a normal vein ?
- venous sinuses have no valves and are formed due to separations of the 2 layers of the dura mater
- veins have valves
Describe subdural haemorrhages
- occur in the space between the dura and arachnoid mater
- likely to have venous origin
Describe subarachnoid haemorrhages
- occurs in the subarachnoid space
- usually due to a burst artery
What is the anterior attachment of the falx cereberi ?
the crista galli
What are the consequences of cavernous sinus thrombosis ?
- it leads to decreased drainage from the facial vein and superior and inferior ophthalmic veins
- this can result in facial and periorbital oedema, discomfort and pain with eye muscle movement and loss of vision
