Session 2 - osteology Flashcards
what method do of ossification do the bones of the calvaria (skull cap or vault) undergo
intramembranous ossification
what method do of ossification do the bones of the cranial floor undergo
endochondral ossification
what is between the inner and outer table of the calvaria
spongy bone called diploe
why are edges of the bones of the skull serrated and at what point do these suture line begin to ossify
prevents slippage and movement
ossify around puberty from inside to outside
what is strongly adhered to the suture line
periosteum and it is continuous from the outer table along the suture line to the inner table
what type of haematoma can extend into the other side of the brain and why
subgaleal (sub aponeurotic) as the heamatoma is above the periosteum
what are fontanelles
they are large areas of unossified membranous gaps between flat bones of calvaria which are present int the infant skull
why is it important that babies have fontanelles
allows for alteration of the skill size and shape during child birth and permit the growth of infant brain
when do the anterior and posterior fontanelles fuse
anterior- 18 months- 2 years
posterior- 1-3 months
what is the rare condition in which you get early fusion of fontanelles and suture called ad why is this porblematic
craniosyntosis
it impedes the development of the brain and alters the shape of the skull
what should be the shape of the anterior fontanelle in a healthy baby and why is it palpated in newborns
slightly convex shape
used to assess intracranial pressure and state of hydration
what are the two main fracture types
linear- pass full thickness of the skull, fairly straight and involve no bone displacement
depressed- fragment is displaced inwards and towards the brain
what is likely to be injured to a basilar skull fracture
cranial nerves
prone to causing CSF leaks
what area of the skull is most likely to fracture
and which blood vessle underlines it
the pterion as it is the thinnest area of skull
middle meningeal artey
what clinical features are seen on a patient with a basilar skull fracture
CSF leaking from nose
racoon eyes
battle eyes
blood behind eardrum
what are the three meningeal layers that surrounds the brain called and what is there appearance like
dura - tough fibrous membrane
arachnoid- soft translucent membrane
pia- microsopically thin, delicate and closely adhered to the surface of the brain
what is the name of the space between the dura and the arachnoid called
the subdural space
what is the name of the space between the pia and the arachnoid called
subarachnoid space
what is found within the subarachnoid space
CSF and cerebral blood vessles
what are the two layers of dura
periosteal- endosteum lining the inner bones of the skull
meningeal- layer adjacent to arachnoid
what does the separation of the two layers of dura form
dural folds
dural venous sinuses (spaces which becomes venous channels)
what feeds into the dural venous sinus and what does the dural venous sinus drain into
the cerebral veins feed into the dural venous sinus
they dural venous sinus drains into the internal jugular vein
in which cranial fossa does the cerebellum sit
posterior cranial fossa
what are the two dural folds called
falx cerebri-sagitala plane
tentorium cerbelli- transverse plane
why do we have dural folds
helps to stabilise the brain and acts as rigid dividers
what is the negative of having rigid dural folds
a rise in pressure inside the skull can lead to compression and displacement of brain against folds and or through foramen magnus
can lead to herniation of brain though foramen magnum
what is a dural venous sinus
its is space that is created by the seperation of the meningeal and periosteal layers of dura and is filled with venous blood
what is an extrdural haemorrhage and how does it look on CT
extradural haematoma (EDH), also known as an epidural haematoma, is a collection of blood that forms between the inner surface of the skull and outer layer of the dura, which is called the endosteal layer (periosteal dura). bleeding most commonly die to a torn middle meningeal artery (Arterial blood) looks like a lens shape
what is a subdural haemorrhage and how it look on a CT
Subdural haemorrhage (SDH) is a collection of blood accumulating in the subdural space, the potential space between the dura and arachnoid mater of the meninges around the brain.
crescent shaped- cannot go to other side of beain as it
Venous blood- usually from bridging veins
falx cerebri will prevent spread of blood to other side
in what age group is subdural hemorrhage more likely to occur and why
elderly
weaker bridging veins
what is a subarachnoid haemorrhage
usually secondary due to trauma or because of spontaneous rupture of a blood vessel (circle of willis)
blood leaks into subarachnoid space mixing with CSF
sudden and often fatal
arterial bleed
what trasnverses the space between the dura and the arachnoid
bridging veins
