Skull and Cranial Cavity Flashcards
Scalp
Consists of 5 layers
Extends over neurocranium
Quite vascular
Innervation of the scalp
Trigeminal nerve
Spinal cutaneous nerves
Bones of the skull
Neurocranium and viscerocranium 22 bones
Sometimes extra bones
Neurocranium bones
8
- occipital
- 2 temporal
- 2 parietal
- sphenoid
- ethmoid
- frontal
Visceracranium bones
14
- 2 nasal conchae
- 2 nasal bones
- 2 maxilla
- 2 palentine bones
- 2 zygomatic bones
- 2 lacrimal bones
- vomer
- mandible
Foramina of the skull function
Permits nerves and blood vessels to enter or leave the cranial cavity
Divisions in base of skull
Cranial fossa
- Anterior
- Middle
- Posterior
Meninges layers
Dura mater
Arachnoid mater
Pia mater
Role of meninges
Protection
Support network for blood vessels
Forms a fluid filed cavity to cushion and nourish the brain
Brain has to float in CSF so it doesn’t crush nerves below it
2 Dura mater layer
Endosteal layer
Meningeal layer
(closely applied to each other)
Dural sinus is split between containing venous structure
SCALP
Skin
Connective tissue (dense)
Aponeurotic layer
Loose connective tissue
Pericranium
Meningeal layer
Around brain and spinal cord
Endosteal layer
Lines the skull
Doesn’t go down spinal cord
Dura mater nerve supply
CN V (trigeminal)
CN X (vagus)
C1-3
Sympathetic
Dura mater blood supply
Middle meningeal artery
- tiny artery winding throw foramen spinosum to inside of skull
Meningeal layer of dura
Series of folds which divide the cranial cavity
Restrict movement of the brain
- flax cerebri
- tentorium cerebelli
- flax cerebelli
Falx cerebri
Separates cerebral hemispheres
Tentorium cerebelli
Separates cerebellar hemispheres from cerebral hemispheres
Falx cerebelli
Separates cerebellar hemispheres
Dura sensitive to stretching
Anatomical basis of headache
Damage to middle meningeal artery
Extradural haematoma
Tentorial herniation
Caused by space occupying lesion cause herniation of temporal lobe
e.g. tumour
Arachnoid mater
Thin avascular between pia and dura
Loosely applied layer with projections
All structures passing to/ from brain pass through subarachnoid space
Cerebrospinal fluid
Produced by choroid plexus in brain
Contained in subarachnoid space
Arachnoid granulations affect the transfer of CSF to the venous sinuses
Role of CSF
Provides buoyancy to brain protecting it from mechanical forces
Pia mater
Very delicate vascular membrane
Closely invests brain following gyri/ sulci
Cerebral arteries enter brain carrying sheath of pia mater with them
Spinal cord meninges
Dura mater (only meningeal layer)
Arachnoid mater
Pia mater
Form part of covering of spinal nerve roots
Leptomeningitis
Infection and inflammation in the arachnoid and pia mater
(leptomeninges)
Infection may enter the subarachnoid space and enter the blood (septicaemia)
Dural sinuses
Sit between dural fold
Drained blood and CSF from brain via cerebral veins
Communicate with the veins of the skull and scalp
Thick walled endothelium (no valves or smooth)
Drain into internal jugular vein
Blood supply to the brain
Internal carotid artery and vertebral artery
Branches anastomose to form circle of willis
Inside skull there are two terminal branches (anterior and middle cerebral artery)
Vertebral arteries
Pass within cervical passes within cervical vertebrae and enter foramen magnum where they unite to form basilar artery
Come of subclavian arteries
Circle of Willis
Formed by anastomses
2xICA
2xVertebral arteries
Cerebral artery
Each has its own pattern of supply to brain
Anterior cerebral artery supplies
Medial and superior surfaces and temporal pole
Middle cerebral artery supplies
Lateral surfaces and temporal pole
Posterior cerebral artery supplies
Inferior surfaces and occipital pole
Stroke
Embolism in cerebral artery
No anastomosis of cerebral arteries once inside brain
Infant skulls
Lower part of fascial skeleton develops in response to eating actions
Arachnoid granulations
Pops up into dural sinus
Needed to get rid of CSF to venous sinus, eventually to jugular vein to be excreted
Superior sagittal sinus
Sinus at the top of the brain
Confluence of sinuses
Right in the middle of the brain
Blood then goes down left or right
Transverse sinus
Left and right
Drains from confluence of sinuses
Common carotid
Off arch of aorta
Up neck and divides to external and internal
External goes forward
Internal goes straight to brain
