cranial cavity, meninges, & dural venous sinus Flashcards
three membranes surrounding brain and spinal cord
- dura mater: thick, tough, fibrous external layer
- arachnoid: intermediate layer
- pia mater: delicate internal layer
function of meninges
- protect the brain
- framework for blood supply
- enclose the subarachnoid space and contain CSF
layers of dura mater
- endosteal layer: periosteum on inner surface of skull, continuous with periosteum on outside of all major foramina of skull
- meningeal layer: dense, strong, fibrous layer covering brain, continuous with dura mater at spinal cord, four dural unfolding, separate the regions of the brain
- *layers cannot be separated
falx cerebri
- largest dural infolding
- lies in longitudinal cerebral fissure that separates right and left cerebral hemispheres
- ends by becoming continuous with tentorium cerebelli
falx cerebelli
- partially separates cerebellar hemispheres
- small fold lying inferior to tentorium cerebelli
- attached to inferior surface of the tentorium and internal occipital crest
tentorium cerebelli
crescent shape fold which separates the occipital lobes from the cerebellum
diaphragma sellae
- small circular fold of dura mater that forms roof of sella turcica (covering pituitary gland)
- small opening in center allows passage of infidibular stalk of hypophysis (pituitary)
innervation of meninges by–
trigeminal and vagus with a little bit of upper cervical spinal nerves (C2 and C3)
anterior cranial fossa innervated by
V1
middle cranial fossa innervated by
V2 and V3
posterior cranial fossa innervated by
- C2 & C3, supplying dura in proximity to foramen magnum
- meningeal branches of vagus and hypoglossal nerves
diploic veins
located within the diploe of the cranial bones
emissary veins
- route of communication between intracranial veins and extracranial veins (no valves)
- allow for escape of blood from the cranium
- many opening transmit these veins
- examples: mastoid foramen connecting posterior auricular vein to sigmoid sinus; parietal foramen–occipital vein to superior sagittal sinus
veins of the cranium
- extracranial
- emissary
- diploic
- cerebral
dural venous sinuses
- venous channels found within the cranial dura mater (between the periosteal and meningeal layers, at the margin of dural folds)
- receive cerebral and meningeal veins and CSF
- drain into internal jugular veins
superior sagittal sinus (superior longitudinal sinus)
- unpaired area along the attached margin of falx cerebri
- allows blood to drain from lateral aspects of anterior cerebral hemispheres to confluence of sinuses
- cerebrospinal fluid drains thru arachnoid granulations into superior sag sinus and returned to venous circulation
- drains into transverse sinus
transverse sinus
- starts at internal occipital protuberance
- follows tentorium cerebelli to drain to sigmoid sinus
sigmoid sinus
- continuation with the transverse sinus (s shape)
- drains to internal jugular vein
inferior sagittal sinus
located in unattached margin of the falx cerebri and drains to the straight sinus
straight sinus**
- located at the junction of falx cerebri with tentorium cerebelli
- formed by inferior sagittal sinus and Great Vein of Galen and ends in Confluence of Sinuses
occipital sinus
- located in falx cerebelli
- run around the foramen magnum and ends in confluence of sinus
cavernous sinus
- circular sinus surrounded the hypothysis (in both sides)
- Inferior petrosal sinus–connects it to internal jugular vein
- Superior petrosal sinus–connects it to the Sigmoid sinus
Nerves located within the cavernous sinus
oculomotor (III) trochlear (IV) opthalmic (V1) maxillary (V2) abducens (VI) internal carotid plexus of nerves (sympathetic nerves)
the cavernous sinus makes a _____ between both inside the skull (other venous sinuses) and outside the skull (facial veins)
central venous connection
veins in the substance of the brain are tributaries to _____
internal jugular vein
superficial cerebral vein branches
- superior drains into superior sagittal sinus
- middle drains into cavernous sinus
- inferior drains into sphenparietal, cavernous, and superior petrosal sinus
deep cerebral vein
drain internal substance of the cerebral hemispheres and drain into the great cerebral vein of Galen which drains into the straight sinus
superior cerebellar vein
drains into straight sinus
inferior cerebellar vein
drains into the superior petrosal, transverse or occipital sinuses
cerebrospnal fluid
- clear liquid similar to blood
- provides nutrients but less protein and different ion concentration
- formed by choroid plexus of four ventricles of brain
- leaves ventricular system and enter subarachnoid space between arach. and pia
- cushions and nourishes brain and helps maintain balance of extracellular fluid
epidural hemorrhage
extradural hemorrhage (between skull and meninges)
- bleeding from meningeal blood vessels
- lucid interval – conscious–> unconscious
- CT scan diagnosis
- lens shape opacity
subdural hemorrhage
between dura and acrach
- hg. frm cerebral veins
- skull moves as brain doesn’t
- CT scan shows crescent
subarachnoid hemorrhage
- from circle of willis
- sudden severe headache
- spontaneous rupture of blood vessels
- lumbar puncture–blood in CSF
intra cerebral
in brain itself
- due to microaneurysm in cerebral blood vessels (hypertension)
- neuronal deficit
connections of facial vein
- directly to cavernous sinus by superior ophthalmic vein or inferior ophthalmis vein
- indirectly by pterygoid venous plexus by inferior ophthalmic vein or deep facial vein
why is dangerous triangle dangerous?
- blood normally drains from medial angle of eye, nose, lips into facial vein
- facial veins don’t have valves so blood can drain into cavernous sinus which can lead to infection in brain
internal carotid
-begins at bifurcation of common carotid
-ascends the neck to enter the carotid canal
continues forward through cavernous sinus and emerges medial to anterior clinoid process to pierce dura
-divides into anterior and middle cerebral arteries
branches of cerebral portion of internal carotid
- opthalmic
- anterior choroidal
- anterior cerebral
- middle cerebral
- posterior communicating
vertebral artery
- comes off subclavian, ascends the neck to enter the foramen magnum and pierces meninges and continues to medulla
- ends in pons and joins the opposite side to form basilar artery
branches of vertebral artery
- posterior spinal
- anterior spinal
- posterior inferior cerebellar artery
basilar artery
- pontine
- labyrintheine
- anterior inferior cerebellar artery
- superior cerebellar artery
- posterior cerebral artery
circle of willis
- anastomoses between internal carotid and vertebral artery
- allows for either the internal carotid or the vertebral arteries to supply any part of the cerebral hemispheres
what does the circle of willis consist of?
- anterior communicating
- anterior cerebral
- internal carotid
- posterior communicating
- posterior cerebral
- basilar arteries
olfactory nerve associated with
telencephalon (cerebrum)
optic nerv assoc with
diencephalon
III and IV originate in
midbrain
V, VI, VII, VIII originate in
pons
IX, X, XI, XII originate in
medulla
III, VII, IX, X contain ____ fibers
preganglionic parasympathetic fibers
cell bodies of all general sensory neurons are located in the ganglia of —–
V, VII, IX, X
cell bodies of taste neurons are located in the ganglia of —–
VII, IX, X
cell bodies of motor neurons are located in separate nuclei within the _____
brainstem (multipolar)
V1 exits through
superior orbital
V2 exits through
rotundum
V3 exits through
ovale
CN III, IV, V1, and VI exit through
superior orbital fissure
