1. MBBS, Batch 17 Year II Dr. Wai Wai Kyi
Meninges and Blood Supply of the Brain
MBBS, Batch 17
Year II
Dr. Wai Wai Kyi

2. Meninges and blood supply to the brain
Objectives:
To discuss the meninges, dural folds, circle of Willis and the dural
venous sinuses within the cranial cavity.
Learning Outcomes
At the end of this lecture, students should be able to:
Enumerate the meninges of brain.
Compare the duramater of brain and spinal cord.
Describe the meningeal and endosteal layers of duramater of the brain.
Describe the formation, functions and contents of the dural folds.
Describe the location, formation and branches of circle of
Willis.
Discuss the position, relations, connections and clinical significance of the dural venous sinuses within the cranial cavity.
Describe arterial supply of the brain and spinal cord.

3. Protection of the Brain
The brain is protected from injury by
The skull (Bone)
Meninges
Cerebrospinal fluid (Watery cushion)
Blood-brain barrier

4. Meninges
The brain and spinal cord are surrounded by three connective
tissue membranes, the meninges (singular, meninx).
■ Brain (cranial meninges)
■ Spinal cord (spinal meninges)
1. Dura mater (tough mother)- outermost, tough membrane
2. Arachnoid mater (spider mother) - spider web filamentous layer
3. Pia mater (gentle mother) - thin vascular layer adherent to contours of brain.
Pia + arachnoid = called
leptomeninges.
Arachnoid = Greek words
which mean spider-like.

5. Functions of the meninges Cover and protect the CNS
Protect blood vessels and enclose venous sinuses
Contain cerebrospinal fluid (CSF)
Form partitions in the skull
Dura mater
Skull bone

6. Dura mater

7. Cranial dural septa The inner layer of dura mater is folded and modified into: 1. Falx cerebri 2. Tentorium cerebelli 3. Falx cerebelli 4. Diaphragma sellae The dural septa extend inward & limit excessive movement of the brain.

8. Dura mater - Falx cerebri
Sickle-like form that dips into the longitudinal fissure.
Separates 2 cerebral hemispheres above the corpus callosum.
Attached anteriorly to the crista galli (of ethmoid bone) and posteriorly to the internal occipital protruberance and along the roof of the cranium.
The broad post. part. is connected with the upper surface of the tentorium cerebelli.
Upper border enclose the
superior saggital sinus,
lower margin is free and
concave and contains
the inferior sagittal sinus.

9. Dura mater - Tentorium cerebelli
The tentorium cerebelli is a crescent-shaped fold of dura mater that roofs over the posterior cranial fossa. It covers the upper surface of the cerebellum and supports the occipital lobes of the cerebral hemispheres. The falx cerebri attaches to the cerebellar tentorium and holds it up, giving it a tent-like appearance (L. tentorium, tent).
In the anterior edge there is a gap, the tentorial notch, for the passage of the midbrain which produces an inner free border and an outer attached or fixed border.
Tentorium cerebelli

10. Dura mater - Tentorium cerebelli (Cont.) Attachments:
■ The fixed border is attached to the margins of the grooves for transverse
sinuses, to the superior edge of petrous temporal bone where it encloses
superior perrosal sinuses and to the post clinoid processes of sphenoid bone.
■ The free border extends forwards to the ant clinoid processes, crossing the
attached border.The triangular interval bet. free & attached borders is pierced
by oculomotor & trochlear nerves.
Ant. Clinoid
process
Post. clinoid process
Free margin of
tentorium cerebelli

11. Dura mater -Tentorium cerebelli (Cont
Dura mater -Tentorium cerebelli (Cont.) ▪ The falx cerebri and the falx cerebelli are attached to the upper and lower surfaces of the tentorium respectively. ▪ It encloses ○ Superior petrosal sinuses – along its attachment to the petrous bone ○ Straight sinus - along the attachment to falx cerebri ○ Transverse sinuses - along its attachment to the occipital bone.
Tentorial notch

12. 3. Dura mater - Falx cerebelli
Small sickle-shaped fold of dura mater
Continuation of falx cerebri, partly separating the two cerebellar hemispheres.
Base is attached to posterior part of inferior surface of tentorium cerebelli.
Apex reaches till foramen magnum
It’s post. fixed margin encloses occipital sinus.
Intercavernous
sinuses
Falx cerebelli

13. 4. Dura mater - Diaphragma sellae (Sella turcica is named for its
Circular fold of dura mater that forms the roof for the sella turcica of the sphenoid bone
A small opening in the center
allows passage of the stalk of the pituitary gland.
Anteriorly attached to tuberculum sellae
Posteriorly to dorsum sellae
Laterally continues with dura mater of middle cranial fossa
It encloses the anterior and
posterior intercavernous sinuses
(Sella turcica is named for its
resemblance of the Turkish
saddle with its anterior
tuberculum sellae, central fossa
and posterior dorsum sellae).
Dorsum sellae

14. Hypophyseal fossa - depression in which the pituitary gland rests (seatof saddle).
Tuberculum sellae - anterior border of the sella turcica (horn of saddle).
Dorsum sellae - posterior border of the sella turcica (back of saddle).
Turkish saddle

15. Dural arterial supply
Meningeal arteries supply the intracranial dura, usually arise
from the branches of external carotid artery.
1. Middle meningeal artery, branch of maxillary artery is the major blood supply to the dura mater. It enters the cranial cavity through the foramen spinosum and lies bet. the meningeal and endosteal layers of the dura. It then runs in a groove on the squamous part of the temporal bone.
The middle meningeal artery is commonly damaged in head injuries.
2. Meningeal branches of vertebral, ophthalmic, anterior ethmoidal, internal carotid, ascending pharyngeal, occipital and accessory meningeal.
Dural venous drainage
Middle meningeal vein drains into the pterygoid venous plexus or
the sphenoparietal sinus.

16. Dural arterial supply

17. Dura mater – Blood supply

19. Dural Nerve supply
Trigeminal nerve, V1, V2 & V3
Upper three cervical nerves, cervical part of the sympathetic trunk
Vagus [X].
Dural headache
▪ The dura mater possesses numerous sensory endings that are sensitive to stretching which produces the sensation of headache.
▪ Stretching the dura above the level of the tentorium cerebelli can produce referred pain along the trigeminal nerve to an area of skin on the same side of the head.
▪ Stretching the dura of below the level of the tentorium produces
referred pain to the skin of the back of the neck and back of the scalp along the distribution of the great occipital N.

20. Cranial Nerves – relation to dura

21. Cranial Nerves – relation to dura

22. Arachnoid mater

23. Arachnoid mater
The arachnoid mater is a delicate, impermeable membrane covering the brain and lying between the pia mater internally and the dura mater externally.
It is separated from the dura by a potential space, the subdural space, filled by a film of fluid; it is separated from the pia by the subarachnoid space, which is filled with cerebrospinal fluid.
The arachnoid bridges over the sulci on the surface of the brain, and in certain situations, the arachnoid and pia are widely separated to form the subarachnoid cisternae. The cisterna cerebellomedullaris lies between the inferior surface of the cerebellum and the roof of the fourth ventricle. The cisterna interpeduncularis lies between the two cerebral peduncles.
In certain areas, the arachnoid projects into the venous sinuses to form arachnoid villi. The arachnoid villi are most numerous along the superior sagittal sinus. Aggregations of arachnoid villi are referred to as arachnoid granulations.

24. Meningeal spaces
Subarachnoid space (SAC)
Contains cerebral blood vessels and CSF.
Surrounds the entire brain & spinal cord.
Extends in the adult below the conus medullaris to the level of the 2nd sacral vertebra, the lumbar cistern.
The fine threads of tissue that spread across this space resemble a spider web (arachnoid= spidery).
SAS surrounds each cranial nerve for a short distance at its foramen. Around the optic nerve the space reaches as far as the eyeball; the central retinal artery & vein cross it. Increased intracranial pressure may compress the vein causing odema of the optic disc, papilloedema.
Rupture of cerebral vein or artery leads to subarachnoid hemorrhage.Condition may be due to trauma, congenital abnormalities (aneurysms), high blood pressure. usually following rupture of an aneurysm of the circle of Willis

25. Meningeal spaces Cont.
Subdural space
Intracranially transmits superior cerebral veins to the superior sagittal sinus. Lacerations of these bridging veins results in subdural hemorrhage ( hematoma).
Spinal epidural space
Located bet. the dura & the vertebral periosteum
Contents: areolar tissue, vertebral venous plexuses,lymphatics, spinal nerves on each side pass through the epidural space
which is applicable for local anaesthetic, epidural anaesthesia.

26. Serve as sites where cerebrospinal fluid diffuses into bloodstream.
Arachnoid
granulation
Serve as sites where cerebrospinal fluid diffuses into bloodstream.
Dura mater
Cells of
arachnoid mater
Cells of
arachnoid mater
Subarachnoid
space

27. Haemorrhage of the brain
Epidural hematoma (extradural hemorrhage) - tearing of the meningeal vessels, especial middle meningeal artery
. Usually due to blow to the side of the head at the pterion (area where skull is thinnest/easiest to fracture). Fracture may rupture the anterior branch of middle meningeal artery ; accumulation of arterial blood in the potential space between dura mater and skull bone.
Subdural hematomas (Veins) – tears in bridging veins that cross the subdural space; accumulation of blood between the dura and the arachnoid.
Meningitis- Inflammation of the meninges .

28. (Bridging veins)

29. Pia mater It is a delicate highly vascular connective tissue layer.
Closely applied to the outer surface of the brain,and spinal cord, follows the contours of gyri & sulci the cortex
Connected to arachnoid by trabeculae.
Carries the blood vessels into the brain.
Forms [with the ependymal cells of the brain and the blood vessels] the choroid plexus.
Subarachnoid space (The space that separates the arachnoid and pia) where the CSF flows.

30. Cranial dural venous sinuses

31. Cranial dural venous sinuses
Located bet. the 2 layers of a dural fold (meningeal & endosteal layers of the dura mater).
Lined by endothelium and have no valves.
Drain into internal jugular veins.
They receive cerebral, diploic, meningeal tributaries and through skull foramina communicates via valveless emissary veins with extracranial vessels.
Cutaneous sepsis may thereby cause infective thrombosis of an intracranial sinus

33. Dural Venous Sinuses Unpaired sinuses Superior sagittal sinuses
Inferior sagittal sinuses
Straight sinus
Sinus confluens
Paired sinuses
Cavernous sinus
Superior petrosal sinuses
Inferior petrosal sinuses
Transverse sinuses
Sigmoid sinuses

34. The meninges of spinal cord

35. The meninges of spinal cord
Spinal dura mater
Spinal arachnoid mater
Spinal pia mater

36. Spinal dura mater Spinal dural sheath, a single layer which
is the continuation of the meningeal layer
of cranial dura.
Does not have a endosteal layer
No dural venous sinuses
No dural septa.
Supplied by spinal brs of segmental arteries (cranial dura - middle meningeal artery).
Epidural space - space between the dura and the periosteum, especilly large the level of S2 vertebra. Local anaesthetic can be injected, epidural anaesthesia.
Subarachnoid space -space bet. dura and arachnoid mater, extends to S2 vertebra.
Contains cerebrospinal fluid (CSF) & blood vessels.

37. Spinal dura mater ( Cont.)
The dura extends for a short distance along the cranial & spinal nerves. In spinal nerves it extends along the nerve roots up to the dorsal root ganglion & in trigeminal nerve it extends up to trigeminal ganglion.

38. Spinal arachnoid mater
A delicate vascular membrane that closely invests the spinal cord
Above, it is continuous with cerebral arachnoid mater.
Spinal pia mater
Denticulate ligament:
Consists of two lateral flattened bands of pial tissue between anterior and posterior roots of spinal nerves attached to the dura with 21 teeth; help to fix position of spinal cord.

39. Spinal pia mater Filum terminale
An extension of pia beyond conus medullaris, descends through the cauda equina to be attached to the coccyx.

40. Blood-Brain Barrier
Consists of
Continuous endothelium of capillary walls, endothelial cells
joined by tight junctions.
Thick basal lamina around each capillary.
Regulated by foot processes of astrocytes, stimulate tight
junction formation between endothelial cells.
Absent at vomiting center (brainstem) and hypothalamus, where blood contents need to be sampled.
Blood-brain barrier
Special anatomy of CNS capillaries which limit exchange
Capillaries= Sites of exchange between blood and interstitial fluid

41. Blood-Brain Barrier