Cranial Cavity-Wed, Sept 27

Front 1

Osteology: Fossa of cranium

Back 1

1. anterior-houses frontal lobes
2. middle-temporal lobes
3. posterior-brain stem, cerebellum

Front 2

bones of Interior skull and fossa:

Back 2

1. frontal bone
2. ethmoid bone-"sieve"
3. sphenoid bone-"wedged between"
4. temporal bone-"time"
5. parietal bone
6. occipital bone

Front 3

Fossa boundaries:

Back 3

1. anterior: anterior portion of frontal bone constructs anterior part of anterior fossa; posterior line is lesser wing of sphenoid; includes the ethmoid
2. middle: anterior border is lesser wing of sphenoid; posterior border is petrous ridge of temporal bone; includes parietal bone
3. posterior: extends from petrous ridge to back of the skull (occipital)

Front 4

Major Landmarks:
Crista galli

Back 4

"comb of the cock"
**protrusion of ethmoid
**attachment of a specialization of intracranial dura mater

Front 5

olfactory foramina

Back 5

*perpendicular plate of ethmoid for passage of minute CN I fibers from nasal cavity
*CNI-made of ~20 filaments and pass thru cribiform plate of ethmoid

Front 6

superior orbital fissure

Back 6

*slit between lesser and greater wings of sphenoid
*conveys structures between orbit and cranium
*CNIII, IV, V1, VI

Front 7

optic foramen

Back 7

**medial to SOF
**~11mm
**optic nerve (CNII) and ophthalmic artery

Front 8

Sella Turcica

Back 8

*posterior to optic foramen in midline
*depression in sphenoid
*houses pituitary gland

Front 9

foramen rotundum

Back 9

**CNV2

Front 10

foramen ovale

Back 10

**CNV3

Front 11

foramen spinosum

Back 11

*entrance for middle meningeal artery

Front 12

Carotid Canal

Back 12

**posterior-medial to sphenoid bone in the petrous temporal bone
**ICA enters cranium
**interal carotid nerve plexus

Front 13

foramen lacerum

Back 13

*in vivo, filled with connective tissue
*post-mortem, just foramen

Front 14

Internal Auditory Meatus

Back 14

**posterior to carotid canal
**CNVII, VIII

Front 15

Jugular foramen

Back 15

*posterior to IAM
*pseudoforamen formed by occipital and petrous portion of temportal bone
*CNIX, X, XI
*IJV

Front 16

Hypoglossal canal

Back 16

**medial to jugular foramen
**CNXII

Front 17

Foramen Magnum

Back 17

*largest foramen of skull
*vertebral arteries ascend
*brain stem becomes spinal cord

Front 18

Clinoid processes of sella turcica

Back 18

1. anterior: tuberculum sellae associated with it; anterior to concavity of sella turcica
2. posterior: lateral extension of posterior portion of sella turcica called dorsum sellae

Front 19

Grooves of skull

Back 19

1. middle meningeal artery, branch of maxillary, supplying skull and dura Mater
2. venous sinuses and arachnoid granulations

Front 20

Infant Skull

Back 20

1. Fontanelles: i)anterior-largest, diamond shaped; allows aspiration of fluid to test for infections; ii)posterior fontanelles; iii)anteriolateral (sphenoidal); iv)posteriolateral (mastoid)
2. parietal eminence
3. incomplete sutures and fontanelles serve 2 purposes:
a)brain is developing
b)allows passage thru birth canal

Front 21

Fibrous sutures:

Back 21

1. coronal
2. sagittal
3. lambdoid
*lambda-jnctn of sagittal and lambdoid
*bregma-jnctn of sagittal and coronal
*parietal foramina lateral to sagittal suture allow emissary veins to pass

Front 22

Clivus

Back 22

*fusion of occipital and sphenoid bones
*looks like a slide
*brain stem lies just posterior

Front 23

From Skull to Brain:
1. Calvaria

Back 23

**2 layers (outer and inner tables) around a diploic space
**emissary veins communicate between veins in scalp and diploic space
**blood flows inside to outside

Front 24

2. Dura Mater

Back 24

2 layers:
1. periosteal/endostial (outer)
2. meningeal, continuous with dura mater of spinal cord (inner)
**between 2 layers are dural venous sinuses, lined endothelium
**can also lie between 2 meningeal layers
**subdural hematoma

Front 25

Middle Meningeal Artery within dura mater

Back 25

*supplies mostly bone but some dura
*bifurcates in middle cranial fossa to form: anterior and posterior branches
*laceration of MM artery=acute epidural hematoma
*epidural space is a potential space in brain, so anything in there is pathologic

Front 26

3. Arachnoid trabeculae

Back 26

*send fist-like projections (granulations)into dura mater

Front 27

4. subarachnoid space

Back 27

*CSF-turns over rapidly (1/3CC per minute); filtered through venous system; enters dural sinus thru; arachnoid granulatons and recirculated
**CSF made primarily deep in brain by choroid plexuses

Front 28

5. pia mater

Back 28

*only on cortex of brain
*continues into sulci
*arterial blood vessels lie superior to pia

Front 29

Specializaton of Dura Mater

Back 29

1. falx cerebri-separates left and right brain; arises posteriorly from tentorium cerebelli and attaches forward to frontal bone and crista galli
2. tentorium cerebelli-Houses the cerebellum

Front 30

Dural Venous Sinuses

Back 30

*valveless
a. superior sagittal
b. left and right transverse
c. straight sinus-jnctn of falx cerebri and tentorium cerebelli
d. inferior sagittal
e. cavernous sinus
f. petrosal sinuses
g. sigmoid-S shaped, arise from transverse sinuses to become IJV
h. sphenoparietal-under edge of lesser wing
i. basilar-plexus running on clivus
j. midline occipital
k. marginal-runs around foramen magnum; while lying down, drainage via IJV; while standing, drains into marginal plexus and then onto Batson's plexus
**all sinuses drain into IJV

Front 31

Cavernous sinus

Back 31

**only place where artery traverse a vein
**pituitary in center
**ICA looks like 2 lumen but not
**CNIII, IV, V1, VI
**basilar skull fraction-ICA lacerated: introduces high pressure arterial blood which reverse flow of venous blood (Carotid Cavernous Fistula); *pulsing eyeball

Front 32

Triangle of Danger

Back 32

*facial veins can drain back, via superior and inferior ophthalmic veins, into cavernous sinus

Front 33

Innervations

Back 33

1. Trigeminal (CNV) innervates dura mater, primarily in anterior and middle fossas
2. CNX and cervical nerves that travel along route of CNXII innervate posterior fossa
*explains why neck injuries can result in headaches

Front 34

Arterial Supply:
Circle of Willis

Back 34

1. Left and Right ICAs
2. L and R vertebral aa
*vertebral arteries fuse into basilar artery on clivus
*basilar bifurcates into posterior cerebrals; connect to middle cerbral aa via posterior communicating artery
*2 anterior cerbrals joined by anterior communicating artery
***25% does not have circle, so stroke would be devastating