session 1 - lecture Flashcards
* cranial fossa
parts of skull base where areas of brain are seated
*skull foramina
exit and entry holes
*dural sinuses
regions filled with blood from which blood drains back into systemic circulation
*components of the skull
mandible cranium - made of neurocranium with brain in and viscerocranium- known as fascial cranium
*components of the cranium
vault - bit that houses the brain
base of skull - where the brain sits
*bones of the cranium
relate to lobes of brain frontal parietal one on either side occipital at back temporal on sides sphenoid - deep in centre of skull ethmoid - towards top of nose
*describe the bones of the fascial skeleton
maxilla - paired - cheek, above upper teeth
zygoma - paired - 2 cheek bones
nasal - paired - nasal bones at top before cartilaginous parts
lacrimal bones - paired - in he orbit related to drainage apparatus of lacrimal glands
vomer - single bone in middle of skull - point up into nasal cavity
inferior conchae - paired - infolding bones from nasal cavity, increase SA - warm air
palatine bones - paired - top of mouth
mandible - jaw bone
*describe the lacrimal glands
in the top corner of eyes, drain across into medial side and then into nasal cavity
describe fibrous sutures in the skull in adult *
fibrous joints holding bones together, permitting little or no movement
fibrous sutures in infant skull *
not completely fused fontanelles - soft spots on top of head, pulsates anterior close between 18-24months, posterior 2-3months present because skull needs to be able to move in childbirth difficult to break - strong fibrous [image]
*what bone is the forehead
frontal bone
*what can you feel in the occipital bone
a protrusion called the inion
*which bones attach to the teeth
the maxilla and the mandible
*what is the role of the inferior and medial nasal concha
they warm air and humidify it
*what is the external acoustic meatus
where the sound gets directed in towards the tympanic membrane
*describe the temporomandibular joint
allow movement in more than 1 direction for chewing
*describe the location of the lacrimal bone
in the medial side of orbit
*describe ethmoid bone, orbital plate
forms the orbit
what does the saggital suture divide *
the parietal bones
what is the suture dividing the occipital and the parietal lobes*
lambdoid suture
what is the connection between the lambdoid and sagittal suture called *
lambda
why are muscels attached to the occipital bone
to maintain head upright
* where does the medulla exit the cranial cavity
foramen magnum
* where are muscles attachedto to help with chewing
pterygoid plates of sphenoid
* where are the condyles (joint/knuckle) placed
sit on C1 vertebrae - form joint between skull and vertebrae - yes joint - move head up and down
what fossa does the frontal lobe sit in *
the anterior cranial fossa
what fossa does the temporal lobe sit in *
the middle cranial fossa
what fossa does the cerebellum sit in *
the posterior cranial fossa
describe the anterior cranial fossa *
slightly raised because the orbit and eye is beneath it (frontal lobe has orbital gyri too)
ventral side of brain is the ….
bottom side where you can see all the cranial nerves
what foramina are in the ethmoid bone *
holes of the olfactory nerve coming from nasal cavity before synapsing in olfactory bulb and going back via olfactory tract
describe the middle cranial fossa *
has lots of foramina and fissures which cranial nerves go through internal carotid artery goes into the cranial cavity via foramen lacerum,. exit is not directly opposite because carotid goes in, turns and then goes up
foramens for CN to eye in middle cranial fossa *
superior orbital fissure foramen rotundum
foramens to face in middle cranial fossa *
foramen ovale
forman to mandible in middle cranial fossa *
foramen spinosum
artery through the foramen spinosum *
middle meningeal artery high pressure artery - involved in damage to vulnerable part of skull - if damaged can cause fast filling epidural bleed
*general order of the cranial nerves
1-12 from rostral to caudal end so exit in that general place in the head
what does the name acoustic suggest
that it will have something to do with the vestibulocochlear nerve - nerve of balance and hearing
what does the name jugular suggest
the place when the veins are draining out of cranial cavity into neck
foramen ovale
oval hole
what passes through cribiform plate of ethmoid *
olfactory nerve fibres
what passes through optic canal *
optic nerve - including central artery of retina, ophthalmic artery
what passes through superior orbital fissure *
oculomotor nerve, trochlear, ophthalmic division of trigeminal nerve V1, abducent CN, superior ophthalmic vein
what passes through foramen rotundum *
maxillary division of trigeminal nerve V2
what passes through foramen ovale *
mandibular division of trigeminal nerve V3
what passes through the foramen lacerum, sphenopetrosal fissure *
internal carotid artery
what passes through foramen spinosum *
middle meningeal artery and vein
what passes through carotid canal, internal aperture *
internal carotid artery
what passes through the internal acoustic meatus *
facial, vestibulochlear, labyrinthine artery and vein
what passes through the jugular foramen *
glossopharyngeal, vagus, accessory nerve, sigmoid sinus into internal jugular vein
what passes through the hypoglossal canal *
hypoglossal CN
what passes through the foramen magnum *
vertebral arteries, medulla of brain, spinal roots of accessory nerve spinal cord
describe the meninges *
3 layers dura - outermost, tough, durable, thick and inelastic - 2 layers: periosteal (close to skull) and meningeal (close to brain) (largely stuck together) arachnoid mater - elastic, spider like projections subarachnoid space - full of CSF - continuous over surface of the brain to the base of the spinal column
*clinical relevance of difference between the meninges in vertebral column and in cranium
can inject and remove stuff form space in vertebral column to see what’s going on in the brain - lumbar puncture. or put in anaesthetic - spinal anaesthetic or spinal block
*where are the layers of dura not together
at sinuses - filled with blood act as an anchor as well - prevent movement at dural folds
*describe the change in the dura at the foramen magnum
the outer periosteal layer fuses with the skull and it is the meningeal layer that goes down the vertebral column - so largee space between dura and bone in vertebral column
what is the main fold of the meningeal layer called *
falx cerebri - sickle shaped double layer
where does the superior saggital sinus run *
from front to back
what happens at the superior saggital sinus *
there is a penetration from the arachnoid mater so that CSF can be recirculated back into the venous system
how can herniation occur *
if there is a raise in intracranial pressure the tough dural sheets can push the brain through and under tentorial notch, and push part of temporal lobe to brain stem - this is the clinical significance of the tentorial notch some cerebellum can herniate through the foramen magnum
effect of subfalcine herniation
not clinically significant
effect of uncal herniation
affects midbrain - unconsciousness
tonsillar herniation
affects medulla, cardioresp failure
where does blood supply to the meninges come from *
to the arteries that normally supply the face - middle meningeal artey - gets inside cranial cavity. runs past soft spot called pterion - if fractured a large epidural bleed can occur
where is the inferior sagittal sinus *
at the bottom of the falx of the superior sagittal sinus
why are emissary veins important *
they traverse from the outside of the skull to the inside of the cranial cavity - can transmit infection from outside would to inside world - scalp lacerations pose a threat
*describe the cavernus sinus
lots of structures associated many CN travel through so thrombosis could affect any of the CN
*what is the relationship between the carotid canal and the foramen lacerum?
the internal carotid artery goes through both
layers of the scalp *
skin connective tissue aponeurosis loose areolar tissue periosteum
where is the bone of the skull thickest
the occipital region
what is the scalp proper *
the 1st three layers of the scalp that are attached tightly together - forming a single unit
describe the skin layer of the scalp *
outer similar to other skin - and has hair
describe the connective tissue layer of the scalp*
anchors the skin to the 3rd layer contains the arteries, veins and nerves supplying the scalp
describe the aponeurotic layer of the scalp *
has the occipitofrontalis muscle - has a frontal belly anteriorly an occipital belly posteriorly and an aponeurotic tendon - the epicranial aponeurosis connecting the 2 frontal belly begins anteriorly - connects to eyebrows it passes up across forehead becoming continuous with the aponeurotic tendon posteriorly - each occipital belly arises from the lateral part of the superior nuchal line of the occipital bone and the mastoid process of temporal bone - attaches to tendon frontal belly innervated by temporal branches of the facial nerve, posterior belly innervated by the posterior auricular branch
describe the loose connective tissue of the scalp *
separates the aponeurotic layer from pericranium - facilitates movement of scalp proper over calvaria
describe the pericranium *
it is the periosteum on the outside of the calvaria attached to bones of the calvaria but is removable - except in area of the sutures
what is the significance of the scalp blood supply in relation to laceration injuries *
there is a lot of blood supply from the external carotid arteries - so there would be heavy bleeding if there was a laceration also scalp bleeding is very arterial because venous pressure is v low in erect position also the vessels don’t contract when they are lacerated because the dense connective tissue holds them open
what does the coronal suture divide *
the frontal and parietal lobes
what is the point of connection between the coronal and sagittal suture called *
Bregma
what are the boundaries of the cranial fossa *
anterior cranial fossa ends at the SPENOIDAL CREST, in the midline is the anterior edge of the chiastmatic sulcus
middle cranial fossa ends at the SUPERIOR BORDER OF THE PETROUS PART OF THE PETROMASTOID PART OF THE TEMPORAL BONE
describe the floor of the anterior cranial fossa *
made of:
- frontal bone
- cribriform plate of the ethmoid bone
- body and lesser wings of the sphenoid bone
the frontal bone projects anteriorly - frontal crest
posteriorly to this you have the foramen cecum
posterior - have the crista galli, a projection from the ethmoid
lateral to this is the cribiform plate of the ethmoid bone
the rest of the floor is formed by the body and lesser wings of the sphenoid - wings hang over the anterior part of the middle fossa, ending as a sharp point laterally, medially they curve posteriorly as the anterior clinoid process
describe the floor of the middle cranial fossa *
made of sphenoid and temporal lobes
floor in the midline is elevated - body of the sphenoid bone
lateral are depressions made of greater wing of sphenoid and squamous part of the temporal lobe
posterior to body of sphenoid is the sella turcica containing the hypophyseal fossa
superior orbital fissure separates the the greater wing of the sphenoid from the lesser
medially in the temporal bone there is the trigeminal impression in the petrous part of the temporal bone marks the sensory ganglion for the trigeminal nerve
then there are 2 small grooves - the groove and hiatus for the greater and lesser petrosal nerve
the arcuate eminence is a rounded protusion of bone - produced by underlying circular canal of the inner ear
the tegmen tympani marks the thin bony roof of the middle ear cavity
*what is the chiasmatic sulcus
a smooth groove stretching between the optic canals and the body of the sphenoid
*describe the floor of the posterior cranial fossa
mainly temporal and occipital, small contributions from sphenoid and parietal bones
largest and deepest fossa contains brainstem anc cerebellum
anterior border is the clivus and dorsum sellae and the superior border of the petrous part of the temporal bone
clivus is slope of bone from foramen magnum made of occipital and sphenoid
lateral border- petrous part of the temporal bone posteriorly - squamous part of the occipital lobe to the groove for transverse sinus and small parts of the occipital and parietal bones
there is a groove for the inferior petrosal sinus
jugular foramen separates occipital from temporal lobe
running to this are the groove for the sigmoid sinus and the petrosal sinus jugular tubercle - large rounded mound of the occipital bone
condylar canal transmits an emissionary vein
squamous occipital bone has: internal occipital crest, either side of this the floor is concave for the cerebellum.
the crest ends posteriorly as teg internal occipital proturberance from this are the grooves for the transverse sinuses [image]
*identify all of the cranial foramina on the diagram and the structures that they transmit *
image
explain the entrance of cerebral veins into the superior sagittal sinus in relation to subdural haemorrhage *
the superior sagittal sinus receives blood from superior cerebral veins that come from in the subarachnoid space if these veins tear where they enter the sagittal sinus it causes a subdural haematoma
describe the path of the venous sinuses *
blood drains from the superior sagittal, and straight sinuses into the confluence of sinuses at the posterior of the head, then into the transverse sinuses which lead into the sigmoid sinus and then into the internal jugular veins which leave the brain passing through the jugular vertebral foramen
what is the anatomy of the dural sinuses *
there are endothelial lined areas where the periosteal and meningeal layers of the dura are separated by venous blood
describe the dural reflections and list them*
the inner layer of the meninges goes in between sections of the brain and separates them, it supports the brain and forms sinuses for venous drainage - falx cerebri - tentorium cerebelli - flax cerebelli
*what is in the cisternae magna in life
a large well of CSF
*what do the internal carotid arteries supply
anterior part of the brain
what do the 3 branches of the facial nerve supply *
stylomastodoid foramen - facial expression petro-tympanic fissure - tongue -taste, salivary gland pterygoid canal - eye, lacrimal gland
when would you use US to examine the brain
babies - no radiation
also you need the fontenelles so that the US can reach the brain, it would be stopped by the skull in adults
describe the superior sagittal sinus *
in the superior border of the flax cerebri
begins anteriorly at the foramen cecum and ends at the confluence of the sinuses
usually bends to the R to empty into the R transverse sinus
describe the inferior sagittal and straight sinuses *
inferior - inferior margin of the flax cerebri, ends at the anterior ridge of the tentorium cerebelli where it is joined by the great cerebral vein - together they form the straight sinus
straight - continues posteriorly along junction of the flax cerebri and tentorium cerebelli and ends at the confluence of the sinuses - usually bending L to enter the L transverse sinus
*describe the confluence of sinuses, transverse and sigmoid sinuses
superior, straight and occipital sinuses empty into confluence. It is a dilated space at the internal occipital proturbance. drained by the transverse sinuses
transverse drain horizontally
as the transverse sinuses lkeave the surface of the occipital bone they become sigmoid sinuses
sigmoid sinuses end at the beginning of the internal jugular veins
*describe the cavernous sinuses
paired
either side of the sphenoid bone, on either side of the sella tucica
structures passing through the cavernous sinuses are internal carotid artery, abducent nerve
structures in the lateral wall of the cavernous sinuses are the oculomotor nerve, trochlear nerve, opthalmic nerve (V1), maxillary nerve (V2)
subject to damage from inflammation because the structures pass through
on the anterior and posterior sides of the pituitary stalk the intercavernous sinuses connect teh 2 cavernous sinsuses
describe the superior and inferior petrousal sinuses *
superior drains the cavernous sinus into the transverse
inferior - end in the jugular vein. basilar sinus connects the inferior petrosal sinuses to each other and to teh vertebral plexus of veins
