Chapter 14 The Meninges and The Cerebral Spinal Fluid

Chapter 14

The Meninges and The
Cerebral Spinal Fluid

Meninges o

Skull
Dura mater:

Periosteal layer
Meningeal layer
Arachnoid villus
Arachnoid mater
Blood vessel
Pia mater
Brain:
Gray matter
White matter

of the Brain

Subdural space
Subarachnoid
space
Superior sagittal
sinus
Falx cerebri
(in longitudinal
fissure only)

Menin

• three connective tissue
the brain

– lies between the ner

– as in spinal cord, the
–

• dura mater
• arachnoid mater
• pia mater

– protect the brain and
framework for its art

nges

membranes that envelop

rvous tissue and bone
ey are the

r

d provide structural
teries and veins

dura mater

• in cranial cavity – 2 separate layers

– outer periosteal – equivalent to
– inner meningeal – continues int

around spinal cord

– cranial dura mater is pressed c

• no epidural space
• not attached to bone except

turcica, the crista galli, and
• layers separated by dural si

through brain

– folds inward to extend between

• falx cerebri separates the tw
• tentorium cerebelli separate
• falx cerebelli separates the

s

o periosteum of cranial bones
to vertebral canal and forms dural sac

closely against cranial bones

t: around foramen magnum, sella
sutures of the skull
inuses – collect blood circulating

n parts of the brain

wo cerebral hemispheres
es cerebrum from cerebellum
right and left halves of cerebellum

Menin

• arachnoid mater and
to those in the spinal

• arachnoid mater

– transparent membran
– subarachnoid space

mater below
– subdural space sepa

above in some places

• pia mater

– very thin membrane t
brain, even dipping in

– not usually visible wit

nges

d pia mater are similar
l cord

ne over brain surface
e separates it from pia

arates it from dura mater
s

that follows contours of
nto sulci
thout a microscope

Meninges o

Skull
Dura mater:

Periosteal layer
Meningeal layer
Arachnoid villus
Arachnoid mater
Blood vessel
Pia mater
Brain:
Gray matter
White matter

of the Brain

Subdural space
Subarachnoid
space
Superior sagittal
sinus
Falx cerebri
(in longitudinal
fissure only)

Menin

• inflammation of the meninge

– serious disease of infancy &
– especially between 3 month

• caused by bacterial and viru
way of the nose and throat

• pia mater and arachnoid are

• bacterial meningitis can ca
enlarging the ventricles, and

• signs include high fever, sti
intense headache and may
within hours of onset

• diagnosed by examining the

– lumbar puncture (spinal t
space between two lumbar

ngitis

es

& childhood
hs and 2 years of age

us invasion of the CNS by

e most often affected
ause swelling the brain,
d hemorrhage
iff neck, drowsiness, and
progress to coma – death

e CSF for bacteria

tap) draws fluid from subarachnoid
r vertebrae

Brain Ve

Lateral ventricles Copyright © The McGraw-Hill Companies, Inc.

Interventricular Caudal Rostral
foramen
Third ventricle (a) Lateral view
Cerebral
aqueduct
Fourth ventricle
Lateral aperture
Median aperture

Central canal

entricles Cerebrum

. Permission required for reproduction or display. Lateral ventricle

(b) Anterior view Interventricular
foramen
Third ventricle
Cerebral
aqueduct
Fourth ventricle

Lateral aperture

Median aperture

Ventricles o

Copyright © The McGraw-Hill Companies, Inc. P

Rostral (anter

Longitudinal
fissure
Frontal lobe
Gray matter
(cortex)
White matter

Lateral ventricle
Temporal lobe
Third ventricle
Lateral sulcus
Insula

Lateral ventricle

Occipital lobe

(c) Caudal (post

of the Brain

Permission required for reproduction or display.

rior)

Corpus callosum
(anterior part)
Caudate nucleus
Septum
pellucidum
Sulcus
Gyrus

Thalamus

Choroid plexus

Corpus callosum
(posterior part)
Longitudinal
fissure

terior)

Ventricles and Ce

• ventricles – four internal

– two lateral ventricles
hemisphere

• interventricular fo
connects to third v

– third ventricle - single
beneath corpus callos
runs through midbrain
ventricle

– fourth ventricle – sma
pons and cerebellum
runs down through sp

erebrospinal Fluid

chambers within the brain

– one in each cerebral

oramen - a tiny pore that
ventricle

e narrow medial space
sum // cerebral aqueduct
n and connects third to fourth

all triangular chamber between
m // connects to central canal

pinal cord

Ventricles and Ce

• choroid plexus – spon
capillaries on the ceilin

• ependyma – neuroglia
and covers the choroid
of the cerebrospinal flu

erebrospinal Fluid

ngy mass of blood
ng of each ventricle

a that lines the ventricles
d plexus // produces 30%
uid

Cerebrospina

• clear, colorless liquid that f
CNS // also bathes brains

• brain produces and absorb

– 100 – 160 mL normally

– 40% formed in subarac

– 30% by the general epe
ventricles

– 30% by the choroid ple

al Fluid (CSF)

fills the ventricles and canals of
s external surface
bs 500 mL/day
y present at one time
chnoid space external to brain
endymal lining of the brain

exuses

Cerebrospina

• production begins wi
blood plasma throug
the brain

– ependymal cells
so CSF has more
chloride than plas
potassium, calciu
very little protein

al Fluid (CSF)

ith the filtration of
gh the capillaries of

modify the filtrate,
e sodium and
sma, but less
um, glucose, and

Cerebrospinal Fluid

• CSF continually flo
the CNS

– driven by its ow
ependymal cilia
brain produced

• CSF secreted in la
through interventri
ventricle

• then down the cere
fourth ventricle

• third and fourth ve
along the way

d (CSF) Circulation

ows through and around

wn pressure, beating of
a, and pulsations of the
d by each heartbeat
ateral ventricles flows
icular foramina into third

ebral aqueduct into the

entricles add more CSF

Cerebrospinal Fluid

• small amount of CSF fills t
cord

– all escapes through thr

• median aperture an

• leads into subarach
cord surface

• CSF is reabsorbed by ara

– cauliflower-shaped ext
meninx // protrudes th

– into superior sagittal si
walls of the villi and mi

d (CSF) Circulation

the central canal of the spinal

ree pores
nd two lateral apertures
hnoid space of brain and spinal

achnoid villi
tension of the arachnoid
hrough dura mater
inus // CSF penetrates the
ixes with the blood in the sinus

Function

• buoyancy
– allows brain to attain con
impaired by its own weig
– if it rested heavily on floo
would kill the nervous tis

• protection
– protects the brain from s
head is jolted
– shaken child syndrome
from severe jolting

• chemical stability
– flow of CSF rinses away
nervous tissue and home
chemical environment

ns of CSF

nsiderable size without being
ght
or of cranium, the pressure
ssue

striking the cranium when the
e and concussions do occur

y metabolic wastes from
eostatically regulates its

Flow of Cereb

Copyright © The McGraw-Hill Companies, Inc. P

1 CSF is secreted by 1
choroid plexus in 2
each lateral ventricle.

2 CSF flows through
Interventricular foramina
into third ventricle.

3 Choroid plexus in third
ventricle adds more CSF.

4 CSF flows down cerebral
aqueduct to fourth ventricle.

5 Choroid plexus in fourth
ventricle adds more CSF.

6 CSF flows out two lateral apertures
and one median aperture.

7 CSF fills subarachnoid space and
bathes external surfaces of brain
and spinal cord.

8 At arachnoid villi, CSF is reabsorbed
into venous blood of dural
venous sinuses.

brospinal Fluid

Permission required for reproduction or display. Arachnoid villus

8 Superior
sagittal
sinus

Arachnoid mater

Subarachnoid
space

Dura mater

3 Choroid plexus
4 Third ventricle

65 7
Cerebral
aqueduct
Lateralaper ture

Fourth ventricle

Median aperture

7

Centralcanal
of spinal cord
Subarachnoid
space of
spinal cord

Blood Supply

• brain is only 2% of the
receives 15% of the blo

• neurons have a high d
therefore, oxygen and
supply of blood is critic

– 10 second interrupt
cause loss of consc

– 1 – 2 minute interru
significant impairme

– 4 minutes with out
brain damage

y to the Brain

adult body weight, and
ood // 750 mL/min

demand for ATP, and
glucose, so a constant
cal to the nervous system

tion of blood flow may
ciousness

uption can cause
ent of neural function

blood causes irreversible

Brain Barri

• blood is also a source of a
bacterial toxins, and other

• brain barrier system – st
substances can get from t
tissue fluid of the brain

• two points of entry must b

– blood capillaries throu

– capillaries of the choro

ier System

antibodies, macrophages,
r harmful agents
trictly regulates what
the bloodstream into the

be guarded:
ughout the brain tissue
oid plexus

Brain Barri

• protects blood capillaries th

– consists of tight junction
form the capillary walls

– astrocytes reach out an
perivascular feet

– induce the endothelial c
completely seal off gaps

– anything leaving the blo
and not between them

– endothelial cells can e
passing to the brain tiss
ones to pass

ier System

hroughout brain tissue
ns between endothelial cells that

nd contact capillaries with their

cells to form tight junctions that
s between them
ood must pass through the cells,

exclude harmful substances from
sue while allowing necessary

Brain Barri

• blood-CSF barrier – an
to protects the brain at
plexus

– form tight junctions

– tight junctions are a
elsewhere

– important to allow e
tissue and CSF

– Note: no CSF-brain

ier System

nother type of barrier designed
t the level of the choroid

s between the ependymal cells
absent from ependymal cells

exchange between brain

n barrier

Brain Barri

• blood barrier system is hig
glucose, and lipid-soluble
oxygen, carbon dioxide, a
and anesthetics

• slightly permeable to sodi
and the waste products ur

• obstacle for delivering me
antibiotics and cancer dru

• trauma and inflammation
pathogens to enter brain t

ier System

ghly permeable to water,
e substances such as
alcohol, caffeine, nicotine,

ium, potassium, chloride,
rea and creatinine

edications such as
ugs

can damage BBS and allow
tissue

Brain Barri

• Circumventricular o

– places in the third an
blood brain barrier is

• blood has direct

• enables the brain
fluctuations in bl
and other variab

• CVOs afford a ro
human immunod

ier System

organs (CVOs)

nd fourth ventricles where the
s absent

access to the brain

n to monitor and respond to
lood glucose, pH, osmolarity,
bles

oute for invasion by the
deficiency virus (HIV)