Cranial Cavity, Meninges, and Dural Sinuses Flashcards
90% of brain size is reached by what age?
5 years old
What is Pterion?
a cranial metric point used for clinical orientation
* frontal, spheoid, temporal and parietal bones all meet
What bone structure houses the pituitary gland?
hypophyseal fossa
What is the name of the epicranial aponeurosis? What does it connect?
gala aponeurotica
*connects the frontalis muscle and occipitalis muscle
frontalis muscle vs occipitalis muscle insertion points?
Why are these points important?
- frontalis muscle: inserts superficially IN SKIN
- occipitalis muscle: inserts into bone
- *important for location of bleeds and infection; since fontalis inserts in skin it allows blood to flow towards face (occipitalis doesn’t bc bone connection stops it)
What does S.C.A.L.P. stand for?
- Skin= Contains hair follicles, sweat and sebaceous glands
- Connective (subcutaneous) tissue= Thick, dense, richly vascularized and innervated subcutaneous layer
- Aponeurosis= Strong, tendinous sheath which serves as attachment for muscles
- Loose areolar tissue= Sponge-like layer that allows free movement of the 1st three layers
- Pericranium= Dense layer that forms the external layer of the neurocranium
What part of S.C.A.L.P. makes the scalp proper? is in contact with bone?
- S.C.A. = scalp proper
* Pericranium in contact with cranium bone
Where is BS to scalp located in what layer? comes from?
BS to the scalp is from both internal and external carotid’s (with external being all superficial structures)
**Blood runs in 2nd layer above gala aponeurotica!
Why does the scalp bleed so much?
Arterial walls are firmly attached to the connective tissue in which they are embedded. Therefore, they have a limited ability to constrict if cut and will bleed profusely.
Why do deep scalp wounds will gape widely when the epicranial aponeurosis is lacerated in the coronal plane?
because of the pull of the frontal and occipital bellies of the occipitofrontalis muscle
Scalp bleeding/Infections CAN and canNOT spread where?
- *CAN spread to the eyes and nose bc the frontalis muscle inserts into the skin/subcutaneous tissue
- *canNOT spread to neck bc the occipital belly of the occipitofrontalis muscle inserts directly to bone
- *canNOT spread laterally bc the epicrania aponeurosis is continuous with the temporal fascia that attaches to the zygomatic arches
Any kind of blood or infection will spread what direction in scalp?
anteriorly
*NOT laterally or posteriorly
What is the FIRST line of defense for head? But what is the MAJOR defense?
skin is first line of defense
*But the bone is the real deal
what does diploe mean?
diploic means two layers of compact bone separated by spongy
*ALL flat bones
Emissary Vein vs Diploic veins
- Diploic veins - running within the spongy bone
- Emissary veins - draining from the scalp inwards
Emissary veins connect dural venous sinuses with veins outside of? What is the name of holes they pass through?
the cranium
- the are NOT within the dura (diploic veins are); but pass through the cranium!
- **emissary foramina in parietal bones connecting dural sinuses to scalp veins
What are meninges? What do they do?
membranes covering the brain and spinal cord
1) protect brain
2) support the vessels and venous sinuses
3) enclose the subarachnoid space
layers of cranium start with skin to brain
- skin
- connective tissue (dense, subcutaneous)
- aponeurosis
- loose connective tissue
- pericranium
- periosteum
- diploic bone
- periosteal layer of dura mater
- meningeal layer of dura mater
- subdural space (ONLY potential)
- arachnoid mater
- subarachnoid space with CSF fluid
- pia mater
- cerebral cortex (Gray matter)
dura vs arachnoid vs pia mater
- dura=2 layers, outermost
- arachboid= shiney, pressed up against meningeal
- pia mater= not visible to naked eye bc connected to brain, few cells thick
venous sinuses form between?
the two layers of dura mater (periosteal and meningeal)
what are arachnoid granulations/villus?
projections of arachnoid mater that go through the meningeal layer into venous sinuses and drain venous sinuses
what is the choroid plexus? found where?
specialized ependymal cells that produce CSF
*found in VENTRICLES
What is found in subarachnoid space?
where all the cerebral arteries are, the circle of Willis, and circulating CSF
Function of CSF
- Mechanical protection
- Pathway for removal of brain metabolites
What is calveria?
What are granular foveolae?
calveria= skull cap
*granular foveolae are depressions on inside of calveria from archnoid granulations
1) Falx cerebri
2) Tentorium cerebelli
3) Falx cerebelli
1) Between hemispheres
2) Tent over the cerebellum; between cerebrum and cerebellum
3) Between cerebellum hemispheres
Drainage of CSF?
INTO confluence of sinuses:
--Superior Sagittal Sinus
--Straight Sinus
-Great Cerebral Vein
-Inferior Sagittal Sinus
--Occipital Sinus
OUT of confluence of sinuses:
1) Transverse sinuses (usually left is dominant)
2) Sigmoid Sinuses, then…
3) jugular foram
4) INTERNAL JUGULAR VEINCavernous sinusus drain? What drain into it? Location?
the orbits
- superior opthalmic vein and facial vein drain into it
- either side of hypotheseal fossa
Danger Zone of the Face
It is possible (although rare) for retrograde infections from the nasal area to the brain (meningitis). This is possible because of the venous communication (via the ophthalmic veins) between the facial vein and the cavernous sinus.
What is BS to meninges and cranium?
middle meningeal artery
define epidural hemorrhage. How do you get it?
Blood leakage between the external periosteal layer of the dura and calvaria
- ABOVE dura mater (lens shaped)
- A blow to the pterion can shear the middle meningeal artery leading to an epidural hemorrhage
define subdural hemorrhage. How do you get it?
BETWEEN dura and arachnoid mater by FORCING a space
*Subdural hemorrhages or hematomas usually follow a blow to the head that jerks the brain inside the cranium injuring it. Usually from damage to a cerebral vein or an emissary vein
Big different between epidural and subdural hemorrhage?
- epidural caused by shearing of middle meningeal artery
* subdural caused by damage to cerebral or emissary vein
define subarachnoid hemorrhage. How do you get it?
usually results from rupture of a cerebral artery
*can be caused by berry anorism OR any rupture of circle of Wilis branches… die very fast, blood spreads fast
