The meninges are composed of three layers from outer to inner: the dura mater, arachnoid mater, and pia mater. The dura mater is the thick outer layer that divides the cranial cavity into spaces. It forms folds like the falx cerebri and tentorium cerebelli. The arachnoid mater is a thin, transparent layer fused to blood vessels. The pia mater is a delicate layer that enters brain sulci. Cerebrospinal fluid circulates through the subarachnoid space between the arachnoid and pia mater, providing protection and buoyancy to the brain.

1. MENINGES
Outer to inner
Dura mater (mother) Arachnoid Pia
(Pachymeninx)
Leptomeninges( Delicate)Leptomeninges( Delicate)

2. Dura Mater
• Thickest , inelastic , dense
• Outer surface is rough & inner smooth
• Cranial & spinal layers-Unite at foramen magnum
Cranial Spinal
Inner OuterInner
Meningeal
Outer
Endosteal
Falx cerebri Tentorium
cerebelli
Falx
cerebelli
Diaphragma
sellae

3. • The endosteal & meningeal layers are united except where
they enclose venous sinuses.
• Endosteal layer
• sends septa to cranium.
• Firmly attached to sutures, base of skull, foramen
magnum.
• As the age advances, it becomes thick & adheres more• As the age advances, it becomes thick & adheres more
firmly to cranium
• Continuous with pericranium & orbital periosteum
• Dura of optic nerve is continuous with sclera

4. Endosteal
layer

5. • Meningeal layer
• Provides sheath to cranial nerves
• Fuses with the epineurium
• Divides cranial cavity into spaces in which different parts
of brain are lodged

6. Falx cerebri
• Between 2 cerebral hemispheres in the sagittal fissure
• Ant-Crista galli
• Post- Tentorium cerebelli (contains straight sinus)
Int occipital protuberance
• Sup.- Sup sagittal sinus
Attached on either side of midline
Sup. Sag.sinus
Attached on either side of midline
• Inf- inf sagittal sinus
Inf.sag.sinus

8. Tentorium Cerebelli
• Tent like fold
• Below occipital lobes of cerebrum, covers sup surface of
cerebellum
• Bet. Ant. Free margin & dorsum cellae is a large hiatus -
Tentorial incisure. Occupied by midbrain
• Attachments• Attachments
1) Outer convex margin- Transverse sulcus of occipital
bones- T. sinus
2) Lat- Sup margin of Petrosal bone-Sup petrosal sinus
3) Forms trigeminal cave at the apex of petrosal bone
4) Ant- Ant & post clenoid process,

9. Crista galli
Ant.clenoid
Post.clenoidPost.clenoid
Petrous
temporal
Transverse
Occipital
sulcus

10. Tentorial
incisure
Tentorium
cerebelli

11. Falx cerebelli
• Below tentorium,in post cerebellar notch
• Attachments- 1) Base- Tentorium cerebelli
2) Post- int occipital crest(Occ.Sinus)
3) Apex – passes at the sides of Fo.
magnum
Occipital sinus

12. Diphragma Sellae
• Forms roof of sella turcica
• Blood supply- 1)Meningeal br of ant & post
ethmoidal
2) Int carotid
3) Maxillary3) Maxillary
4) Lacrimal
5) Vertebral
6) Occipital
7) Ascending pharyngeal

13. • Venous drain- Meningeal
• Nerve supply- Trigeminal / Vagus / Hypoglosal /
Facial/ Glossopharyngeal

14. Spinal Dura Mater
• Attachment – 1) Foramen magnum margin /
bodies of C3,C4
2) Blends with periosteum of coccyx
• Forms atlanto -occipital mem.
• The meningeal layer here becomes periosteum of
vertebral canalvertebral canal
• Hence bet. dura mater & periosteum is epidural space
• So dura mater forms a tubular sheath around spinal
cord & spinal nerves
• At cervical region- Thickest

16. Arachnoid Mater
• Enters only longitudinal fissure
• Thin , transparent
• Thick & opaque at the base
• Fuses with adventitia of carotid, vertebral A.

17. Pia Mater
• Delicate ,enters sulci. Between it & brain is
subpial space containing blood vessels
Spinal Leptomeninges
• Spinal nerves are covered by arachnoid when
they leave vertebral column
• At foramen fuse with perineurium
• Pia mater enters ant. fissure

18. Spaces
1) Extradural- Bet. Spinal dura mater & periosteum.
Contains loose connective tissue, fat & venous plexus
Anesthetic fluid can reach upto cranial base
2) Subdural- Dura & arachnoid. Accidental injections can
cause injury to cord
3) Subarachnoid- Arachnoid & pia –Contains CSF/ larger3) Subarachnoid- Arachnoid & pia –Contains CSF/ larger
arteries & veins

21. Subarachnoid Cisterns
• Gap bet. Pia & arachnoid
• Communicate with general subarachnoid
Cerebello
Medullary/
Pontine Inter
peduncular
Lat fossa Cistern of
GreatMedullary/
Cistern
magna
peduncular Great
cerebral vein
/Cistern
Ambiens/
Sup.cistern

23. • Arachnoid Villi- Extention of arachnoid mater &
space into sinuses(especially sup.sagittal)
• Arachnoid granulations- highly folded arachnoid
,Produce pitting on inner surface of calvaria

24. Cerebro-spinal fluid
• Clear fluid in subarachnoid space
• Brain floats in it
• Formation- Choroid plexus- 50-70%
• Rest- Blood vessels
• Circulation-• Circulation-
Lateral ventricle
3rd ventricle
Foramen of Monro
Cerebral auqeduct

26. 4th ventricle
Subarachnoid space
Foramen of Megendie/Luska
Re absorption in veins via arachnoid granulationsRe absorption in veins via arachnoid granulations
Amount produced- 500ml/day
Brain capacity- 135-150 ml
Contents- 1) Glucose
2) Proteins
3) RBCs
4) WBCs

28. Functions Of CSF
• Wt. reduction – Brain actual wt.- 1400 gm
In CSF-25 gm
• Protection
Applied- 1) MeningitisApplied- 1) Meningitis
2) Lumbar puncture