Learning Issues Week 2 Flashcards
bones of braincase
cribriform plate of ethmoid bone, sphenoid bones (presphenoid and basisphenoid), occipital bones, parietal bones, frontal bones, and temporal bones
braincase
part of skull that houses brain (bone)
cranial cavity
space with in braincase
floor of braincase
presphenoid, basisphenoid, basiocipital bones
rostral boundary of braincase
cribriform plate of ethmoid bone; divides braincase from nasal cavity
olfactory afferents (CN I) pass through
cribriform plate of ethmoid bone
access from nasal cavity to cr cavity
for infectious agents; through cribiform plate of ethmoid bone
sphenoid bones
presphenoid and basisphenoid
rostral 2/3 braincase floor
sphenoid bones
hypophyseal fossa
midline depression basisphenoid bone houses hypophysis (pituitary gland)
dorsum sellae
bony prominence that cdly borders pituitary gland; sits in midline groove btwn crus ceribri
cavernous sinus
venous sinus lateral to hypophyseal fossa
optic canal/ foramen
formed by presphenoid bone, CN II enters skull here
orbital fissure
formed at junction of presphenoid and basisphenoid bones; CN III, IV, VI, and V1 pass through
round and oval foramen
in basisphenoid bone, V2 and V3 transverse respectively
alar canal
in dogs and horses not cats or ruminants; formed in basisphenoid bone; maxillary artery transverses V2 transverses and emerges from rostral alar foramen
what form cd boundary braincase
occipital bones
occipital bones articulate with
atlas and occipital condyles
basisphenoid bone, temporal bones, parietal bone
sphenoid bones contain
- hypophyseal fossa
- Dorsal sell
- Cavernous sinus
- Optic canal/ fissure
- Orbital fissure
- Round and oval foramina
- Alar canal
occipital bones contain
- Tentorium osseum
- Tentorium cerebelli
- Foramen magnum
- Basioccipital bone
- Hypoglossal canal
- Jugular formane
- Tympano-occipital fissure
Tentorium osseum
D bony process extending into cr cavity
tentorium cerebelli
reflection/ fold dura matter; attached at tentorium osseum
foramen magnum
spinal cord emerges through this opening
basioccipital bone
cd 1/3 base braincase; pons and medulla sit on this
hypoglossal canal
CN XII exits cr cavity here
jugular foramen
at articulation basioccipital bone and petrous temporal bone
what exit cranial cavity through jugular foramen
CN IX, X, XI, sigmoid sinus
tympano-occipital fissure
at junction of basioccipital bone and tympanic bulla
what transverses tympani-occipital fissure
CN IX, X, XI, and internal carotid artery, internal jug vein, vertebral vein, and symp fibers from cr cervical ganglion
parietal bones
overlie cerebrum cd dorsally
frontal bones
overlie cerebrum rostrally; form medial orbital wall; contains frontal sinus
temporal bones
form large part ventrolateral braincase
parts temporal pones
tympanic part, squamous part, petrosal part
tympanic part
includes middle ear, doesn’t contribute to braincase, retroarticular foramen, carotid canal
retroarticular foramen
formed at junction with squamous pt temporal bone
carotid canal
at junction with basioccipital bone; contains int carotid artery and symp post ganglionic axons from cr cervical ganglion; these structures travel from tympanooccipital fissure to cavernous sinus w/ in cr cavity
squamous part
articulates with sphenoid, parietal, and occipital bones; overlies temporal lobe neocortex
petrosal part
aka petrosal temporal bone
- petrosal crest= dorsally located
- borders: lat aspect pons and medulla, and cerebellum
petrosal part encases
cochlear ducts and vestibular apparatus
what CN fibers does petrosal part temporal bone carry
fibers CN VIII and CN VII; CNV passes through groove cr cavity w/ in PTB
CN VIII
enters cr cavity via int acoustic meatus= foramen on medial aspect PTB
CN VII
axons exit cr cavity via int acoustic meatus -> PTB in facial canal -> stylomastoid foramen -> exit skull
CN V
passes through groove cr canal with in PTB
trigeminal ganlglia location
located at rostral tip PTB
Jugular foramen
at junction basioccipital bone with PTB
tentorium cerebelli
attached at petrosal crest to PTB
calvaria
D portion./ roof of braincase
meninges
3 CT layers surrounding brain and spinal cord
meningeal layers
dura matter, arachnid, Pia matter
dura matter
fibrous outer meningeal layer= collagenous CT
arachnoid
btwn pia and dura; spans sulci, doesn’t follow surface of brain as closely as pia
pia matter
inner most layer; delicate permeable CT layer; tightly adhered to surface brain and spinal cord tissue
dura in skull
2 fused layers; periosteal layer and meningeal layer; no epidural space bc periosteal layer fused to skull
periosteal layer dura in skull
periosteum of bone fused to inner surface of brain case
meningeal layer dura in skull
inner layer= fused to periosteal layer except at venous sinuses and dural reflections
dura in vertebral colum
dura only one layer meningeal layer; has epidural space
epidural space
between meningeal layer dura and periosteum of vertebrea
inaccurate ligaments
D border epidural space btwn vertebral arches
epidural space contains
fat and internal vertebral venous plexus = system veins convey bld cr cavity and spinal cord -> systemic veins
epidural space clinical use
can inject drugs into this space to inactivate NT or modulate nocioceptiv (pain) transmission
dural reflections
w/ in cr cavity composed of meningeal dura that separates from periosteal dura forming shelf CT w/ in CR cavity
- falx cerebri
- tentorium cerebelli
falx cerebri
separates L and R cerebral hemispheres; contains D sagittal sinus
Tentorium cerebelli
- separates occipital lobe and cerebellum
- spans gap btwn tenurial process occipital bone and petrosal crest
transverse sinus
at junction of tentorium and occipital/ parietal bones
straight sinus
at junction of falx cerebra and tentorium cerebelli
dorsal sinuses
venous channels between layers meningeal dura where diverge from periosteal dura; cerebral veins empty into sinuses, convey blood to peripheral veins
arachnoid cell type
fibroblast derived cells interconnected by tight junctions
-> barrier
arachnoid attachment to meningeal dura
attach via inter-cellular connections
subdural hematoma
hemorrhage with in tissue near junction meningeal dura matter and arachnoid layer -> traumatic separation tissue layers called subdural hematoma (space between these two layers should normally be a potential space in this case the space exists because there is hemorrhage)
arrachnoid connection to pia matter
via collagenous trabeculae= extends through subarachnoid space
subarachnoid space
between pia matter and arachnoid contains blood vessels and CSF
subarachnoid space uses
can inject contrast material into here -> enhanced imaging studies; can collect CSF from here in taps
subarachnoid cisterns
regions where subarachnoid space is larger because increased separation between pia and arachnoid cellular layer
cerebromedullary cistern
angle between cd cerebellum and dorsal brainstem accept for CSF tap via AO space
lumbar cistern
region subarachnoid space extends cd to conus medullar is; contains CSF; film terminals and spinal roots cada equina
pia matter
closely follows contours NT into sulci; blood vessels lie on surface pia matter in subarachnoid space
Fossae
rostra cranial l, middle cranial, cd cr fossae
Rostral cranial fossae floor
formed by presphenoid bone
rostral cranial fossae rostral boundary
cribriform plate
rostral cranial fossae laterally bounded by
frontal bone
optic chiasm
at cd boundary rostral cr fossae with middle cr fossae
rostral cranial fossae contains
olfactory bulb, olfactory peduncle, frontal lobe, optic nerves
rostral cranial fossae is D to
presphenoid bone
middle cr fossae floor
formed by basisphenoid bone
middle cr fossae cd boudnary
dorsal sellae
middle cr fossae laterally bounded by
wings basisphenoid bone
middle cr fossae incldues area
lateral to petrosal crest and medial ot squamous temporal bone
middle cr fossae contains
pituitary gland (hypophyseal fossa), diencephalon, cavernous sinus (and all tis cr nerve and vasculaar contents), piriform and temporal lobes more laterally, crus cerebri
crus cerebra and middle cr fossae and cd cranial fossae
crus cerebri straddle the dorsal sell at junction with cd cr fossae
CNs of middle cr fossae
III, IV, V1, V2, VI, symp post ganglionic fibers -> face
middle cr fosse vasculature
int carotid arteries, maxillary artery (forming rete mirabel with in caverns sinus), veins drain face and nasal cavity
cd cr fosse floor
formed largely by basioccipital bone
cd cr fosse extends
lateral to petrosal crest/ PTB
cd cr fosse dorsally bounded by
tentorium cerebelli
cd cr fosse extends cdly to
foramen magnum
cd cr fosse contains
cd brainstem and cerebellum
cd cr fosse is D to
basioccipital bone
brain divisions of cd cr fossae
mylencephalon, metencephalon, midbrain
CNs of cd cr fossae
VI-X, XII (mylencephalon), CN V (metencephalon), III, IV
sinus between
periosteal dura and meningeal dura
meningeal layers order skull
periosteal dura, meningeal dura, arachnoid cell layer, subarachnoid space, pia matter
ependymal cells
leaky, lack tight junctions
choroid epithelium
not leaky, have tight junecitons
CSF choroid plexus -> venous sinus
CSF in choroid plexus -> lat ventricle -> 3rd ventricle -> MA -> lat recess 4th ventricle -> lateral aperture -> subarachnoid space -> arachnoid villi/ granulation and venous sinuses
Alternate paths CSF
CSF can also enter bran/ spinal cord tissues via ependymal cells (leaky) or pia matter and from there be absorbed by veins within the tissue, some CSF leaks out meningeal cuffs where roots spinal and cr nerves become peripheral nerves
hydrocephalus
obstruction to flow of CSF through ventricles; Choroid plexus will produce CSF at steady rate despite obstruction preventing CSF leave ventricular system via lateral appetites -> ventricles enlarging
what causes hydrocephalus
can occur bc CNS malformation, inflammation, or tumors
what happens when hydrocephalus -> ventricles enlarging
ventricles enlarge b/c increase pressure with in ventricles -> compression brain tissue b/c limited capacity of cr cavity to expand
common site of obstruction of CSF flow
mesencephalic aqueducs; common site of obstruction bc relatively narrow diameter
flow of CSF
flows high pressure to low pressure therefore increased pressure can lead to herniation over tentum ceribelli and herniate into cd cr fossa and out foramen magnum -> disrupt brainstem fx
Can get herniation side to side across fall ceribri
Can get herniation of brain from side to side across
falx cerebri
cerebellomedullary cistern
angle between cd cerebellum and dorsal brainstem access for CSF tap via Atlanto-occipital space
