Meninges + Vascular Supply

Question 1

meninges

Answer 1

three layers of membrane surrounding the brain and spinal cord

Question 2

layers of the meninges

Answer 2

dura mater
arachnoid mater
pia mater

Question 3

functions of the meninges

Answer 3

1. dura - protection from mechanical injury
2. arachnoid - provide space for flow of CSF
3. pia - provide blood supply to the skull and cerebral hemispheres

Question 4

dura mater

Answer 4

outermost, thick membrane composed of two layers
- contains fibroelastic cells
- highly vascularized
- innervated by CN V

PERMEABLE: abundant collagen, no tight junctions

Question 5

functions of the dura mater

Answer 5

1. cover/protect brain and spinal cord
2. regulate neural progenitor migration/generation
3. limit rotational displacement of the brain
4. regulate glial cells
5. regulate axon behavior at CNS/PNS interface

Question 6

layers of the dura

Answer 6

1. periosteal layer
2. meningeal layer

Question 7

periosteal layer

Answer 7

superficial; closest to calvarium

Question 8

meningeal layer

Answer 8

inner layer; closest to CNS parenchyma, contains larger blood vessels

Question 9

dural reflections

Answer 9

folds in the dura that limit rotational displacement of the brain
- falx cerebri/cerebelli: divides hemispheres
- tentorium cerebelli: separates cerebrum/cerebellum

Question 10

arachnoid mater

Answer 10

middle membrane composed of crossing fibers that connect to the pia mater
- IMPERMEABLE: little collagen, has tight junctions

Question 11

functions of the arachnoid

Answer 11

house the arachnoid space (subarachnoid space) for flow of CSF

Question 12

arachnoid membrane

Answer 12

thin, fibrous tissue formed by flat cells that prevent diffusion of CSF

Question 13

arachnoid trabeculae

Answer 13

strands of connective tissue that loosely join the arachnoid barrier cells with the pia mater

Question 14

subarachnoid space

Answer 14

space within the arachnoid mater filled with CSF

Question 15

arachnoid villi/granulations

Answer 15

protrusions of arachnoid membrane that cross the dura into the venous sinuses that allow CSF to be reabsorbed into circulation
- maintains UNIDIRECTIONAL flow of CSF

Question 16

ways to maintain unidirectional flow of CSF from SAS –> venous sinus –> circulation

Answer 16

pressure differences; flows from high to low

subarachnoid space: high pressure
venous sinuses: low pressure

Question 17

arachnoid cisternae

Answer 17

widest portions of subarachnoid space used to collect CSF

Question 18

cisterna magna

Answer 18

clinically important arachnoid cisterna for CSF taps; located at the junction of the atlas and the occipital lobes

Question 19

pia mater

Answer 19

thin, mesh membrane that tightly follows the brain and spinal cord
- follows all gyri/sulci
- interlaced with blood vessels that are important for vascularization of CNS

Question 20

function of pia mater

Answer 20

provides blood supply and helps contain CSF

Question 21

pial sheath

Answer 21

external portion of the blood vessel wall as it pierces the pia to enter the CNS parenchyma
- creates a Virchow-Robin space

Question 22

Virchow-Robin space

Answer 22

space between the pia and the blood vessel

Question 23

clinical conditions of the meninges

Answer 23

1. hematoma
2. meningioma
3. meningitis
4. external hydrocephalus
5. CSF circulation disorders

Question 24

epidural/extradural hematomas

Answer 24

hematoma is located between the skull and the dura mater
- displaces the dura away from the skull
- rapidly expands
- arterial blood

Question 25

subdural hematomas

Answer 25

hematoma is located between the dura and the arachnoid mater - does not displace the dura - slowly expands - venous blood

Question 26

intracerebral/interparenchymal hematoma

Answer 26

hematoma is located within the brain parenchyma

Question 27

meningioma

Answer 27

tumor arising from the arachnoid mater - common - slow growing - treatable

Question 28

meningitis

Answer 28

inflammation of the meninges - usually secondary to bacterial/fungal/protozoan infection

Question 29

aseptic meningitis

Answer 29

viral meningitis ONLY affects the meninges

Question 30

meningoencephalitis

Answer 30

infection affects the meninges AND the parenchyma - usually secondary to nearby infection (ears, eyes, nasal cavity)

Question 31

granulomatous meningoencephalitis

Answer 31

caused by canine distemper

Question 32

external hydrocephalus

Answer 32

accumulation of CSF outside the ventricles cause: impairment of the arachnoid-CSF barrier leading to insufficient drainage of CSF to venous sinuses and accumulation in SAS

Question 33

chiari malformation

Answer 33

structural defect that causes lower part of the brain to press into/through an opening in the base of the skull and into the spinal cord - causes secondary syringomyelia - common in small headed dogs

Question 34

syringomyelia

Answer 34

fluid filled cyst on the spinal cord

Question 35

brain blood supply requirement

Answer 35

large and stable; consumes 25% of O2 intake and 15% of cardiac output

Question 36

main blood supply to the brain

Answer 36

internal carotid and vertebral arteries

Question 37

circle of willis

Answer 37

circular connection between the internal carotid artery and basilar artery at the basal part of the brain

Question 38

internal carotid artery

Answer 38

branch of the common carotid supplies the rostral and middle cerebral arteries

Question 39

basilar artery

Answer 39

supplied by vertebral and ventral spinal arteries supplies the caudal cerebral, cerebellar, and pontine arteries

Question 40

blood flow from aorta --> internal carotid

Answer 40

aorta --> L/R common carotids --> internal/external carotids

Question 41

carotid sinus

Answer 41

dilated area at the base of the ICA just above the ECA/ICA bifurcation contains baroreceptors to detect changes in arterial pressure

Question 42

arterial territories

Answer 42

five main arteries that branch from the circle of willis; supplies distinct regions: 1. rostral cerebral 2. middle cerebral 3. caudal cerebral 4. rostral cerebellar 5. caudal cerebellar

Question 43

cerebrovascular accidents (CVAs)

Answer 43

strokes; disruption of blood supply to the brain caused by hemorrhage or ischemia

Question 44

function of veins in the brain

Answer 44

carry blood to systemic circulation release blood into sinuses NO valves - movement is facilitated by gravity

Question 45

location of veins in the brain

Answer 45

outside and within parenchyma

Question 46

function of venous sinuses in the brain

Answer 46

CSF resorption empty into internal jugular veins to go back to heart

Question 47

location of venous sinuses in the brain

Answer 47

outside the parenchyma only

Question 48

main dural sinuses

Answer 48

1. dorsal sagittal sinus - along midline 2. confluens sinuum - collection from dorsal sagittal sinus, straight sinus, and occipital sinus 3. transverse sinus - collects from confluens sinuum; drains to internal jugular