01-Lecture .NeuroAnatomy of Meninges of brain and spinal cord

Anatomy of Meninges of brain and spinal cord

2. ANATOMY IV
NEURO ANATOMY
CREDIT HOURS 3(2-1)
Delivered by
Dr. Habib Khan PT
DPT-KMU, MSNMPT_RIU

3. Meninges
•The meninges refer to the membranous coverings of the brain and
spinal cord.
•There are three layers of meninges, known as the dura mater,
arachnoid mater and pia mater.
•These coverings have two major functions:
•Provide a supportive framework for the cerebral and cranial
vasculature.
•protect the CNS from mechanical damage.

5. MENINGES
•The Meninges are the membrane (connective tissues)
covering the brain and spinal cord.
•The Meninges consist of three membranes:
1.The Dura mater,
2.The arachnoid mater,
3.The Pia mater.

7. Dura Mater
•outermost layer of the meninges
•directly underneath the bones of the skull and vertebral column.
•It is thick, tough.
•The dura mater consists of two layered sheets of connective
tissue:
•Periosteal layer – lines the inner surface of the bones of the
cranium.
•Meningeal layer – located deep to the periosteal layer.
•It is continuous with the dura mater of the spinal cord.

8. •The dural venous sinuses are located between the two
layers of dura mater.
•They are responsible for the venous drainage of the
cranium and empty into the internal jugular veins.
•The dura mater receives its own vascular supply –
primarily from the middle meningeal artery and vein. It is
innervated by the trigeminal nerve (V1, V2 and V3).

9. DURA MATER
•Bilaminar:
1.Endosteal layer (outer)
2.Meningeal layer (inner)
•These are closely united except along certain lines, where
they separate to form venous sinuses.

11. Endosteal layer ;
•Periosteum - inner surface of the skull bones
•Not continuous with Dura mater of spinal cord

12. Meningeal layer
•Dura mater proper
•Covering the brain
•Continuous with Dura mater of spinal cord
•Folded inwards as 4 septa between part of the brain
•The function of these septa is to restrict the rotatory
displacement of the brain.

13. DURA MATER SEPTA
1. Falx cerebri
2. Falx cerebelli
3. Tentorium cerebelli
4. Diaphragma sella

14. The Falx Cerebri
•It is a sickle-shaped fold of dura mater that lies in the midline between
the two cerebral hemispheres.
•Its narrow end in front is attached to the internal frontal crest and the
crista galli.

16. The Falx Cerebri
•Its broad posterior part blends in the midline
with the upper surface of the tentorium
cerebelli.

17. The Falx Cerebri
•The superior sagittal sinus runs in its upper fixed margin, the inferior
sagittal sinus runs in its lower concave free margin, and the straight sinus
runs along its attachment to the tentorium cerebelli.

18. The Tentorium Cerebelli
•The tentorium cerebelli is a crescent-shaped fold of dura
mater that roofs over the posterior cranial fossa.

20. The Tentorium Cerebelli
•It covers the upper surface of the cerebellum and supports
the occipital lobes of the cerebral hemispheres.

21. The Falx Cerebelli
•The falx cerebelli is a small, sickle-shaped fold of dura mater that is
attached to the internal occipital crest and projects forward between the
two cerebellar hemispheres.

23. The Tentorium Cerebelli
•Its posterior fixed margin contains the
occipital sinus.

24. The Diaphragma Sellae
•Sella turcica(The sella turcica (Latin for Turkish saddle) is
 
a saddle-shaped
depression in the body of the
 sphenoid bone of the human skull)
•The diaphragma sellae is a small circular fold of dura mater that forms the
roof for the sella turcica.
•A small opening in its center allows passage of the stalk of the pituitary
gland

25. The Diaphragma Sellae

26. Dural Nerve Supply
•Branches of the trigeminal, vagus, and first
three cervical nerves and branches from the
sympathetic system pass to the dura.
•The dura is sensitive to stretching, which
produces the sensation of headache.

27. Dural Arterial Supply
•The dura mater’s arteries supply from the internal carotid,
maxillary, ascending pharyngeal, occipital, and vertebral arteries.
•From a clinical standpoint, the most important is the middle
meningeal artery, which is commonly damaged in head injuries.
•The anterior branch of the middle meningeal artery runs
beneath the pterion. It is vulnerable to injury at this point, where
the skull is thin. Rupture of the artery may give rise to an
epidural hematoma.

30. Dural Venous Drainage
•The meningeal veins lie in the endosteal layer of dura.
•The middle meningeal vein follows the branches of
the middle meningeal artery and drains into the
pterygoid venous plexus or the sphenoparietal sinus.
•The veins lie lateral to the arteries.

32. Clinical Relevance:
•Extradural and Subdural Haematomas
•A haematoma is a collection of blood.
•As the cranial cavity is effectively a closed box, a haematoma can cause a rapid
increase in intra-cranial pressure.
•Death will result if untreated.
•There are two types of haematomas involving the dura mater:
•Extradural – arterial blood collects between the skull and periosteal layer of the
dura. The causative vessel is usually the middle meningeal artery, tearing as a
consequence of brain trauma.
•Subdural – venous blood collects between the dura and the arachnoid mater.
•It results from damage to cerebral veins as they empty into the dural venous
sinuses.

33. Arachnoid Mater
•the middle layer of the meninges
•lying directly underneath the dura mater.
•It consists of layers of connective tissue,
•is avascular
• does not receive any innervation.

34. •The outer and inner surfaces of arachnoid are covered with
flattend Mesothelial cells
•Mesothelial cells are a monolayer of specialized pavement-like
cells
•that often line the body's serous cavities and vital organs.
•The primary role of this layer, called the mesothelium, is to
make a nonadhesive, slippery, and protective surface.

35. •Underneath the arachnoid is a space known as the sub-
arachnoid space.
•It contains cerebrospinal fluid, which acts to cushion the
brain.
•Small projections of arachnoid mater into the dural venous
sinuses to form arachnoid villi .
•Serves as sites where CSF diffuses into the blood stream
•aggregations of arachnoid villi are known as arachnoid
granulations
•allow CSF to re-enter the circulation via the dural venous
sinuses.

36. •the CSF passes between the inner two meningeal layers
(arachnoid and pia) which are together called the
leptomeninges.
•The arachnoid mater does not follow precisely the contours of
the brain.
• Moreover, in certain sites, it completely separates from the
pia mater
• Thus forming the expansions of the subarachnoid space,
called the
 
subarachnoid cisterns.

37. •subarachnoid cisterns of the brain are continuous with each other
through the general subarachnoid space.
•Cisterna magna (cerebellomedullary cistern)
•is located betweeen the inferior surface of the cerebellum and roof
of the 4
th
ventricle
•Interpeduncular cistern: between the two cerebelar peduncle
•CSF FUNCTION:
•removal of waste product
•protection
•hormonal transport
•SPINAL CORD Subarachnoid SPACE extends till 2
nd
sacral vertebra
•The arachnoid fuses with the epineurium of the nerves at their
point of exit from skull.
•Optic nerve

39. Pia Mater
•located underneath the sub-arachnoid space.
• It is very thin
• tightly adhered to the surface of the brain and spinal cord.
•It is the only covering to follow the contours of the brain (the
gyri and fissures).
•Like the dura mater, it is highly vascularised
•with blood vessels perforating through the membrane to
supply the underlying neural tissue.

40. •It doesn’t lie on the surface of the brain directly but rather is separated from it
by a thin space called the subpial space formed by the end-feet of the
astrocytes (glia limitans).
•The
 function of the pia mater is to physically separate the neural tissue from
the blood vessels in the subarachnoid space, adding to the efficacy of the
 
blood-brain barrier.
•Blood-Brain Barrier (BBB) is a
 selectively permeable membrane regulates the
passage of a multitude of large and small molecules into the
microenvironment of the neurons.
•It achieves this with the aid of multiple cellular
 transport channels scattered
along the membrane.

41. Clinical Relevance:
Meningitis
•Meningitis refers to inflammation of the meninges.
• It is usually caused by pathogens, but can be drug induced.
•Bacteria are the most common infective cause.
•The most common organisms are Neisseria meningitidis and
Streptococcus pneumoniae.
•The immune response to the infection causes cerebral
oedema, consequently raising intra-cranial pressure.

42. •This has two main effects:
•Part of the brain can be forced out of the cranial cavity – this
is known as cranial herniation.
•In combination with systemic hypotension, raised intracranial
pressure reduces cerebral perfusion.
•Both complications can rapidly result in death.

44. Spinal cord Meninges
•Distally, the meninges form a strand of fibrous tissue, the filum terminale,
which attaches to the vertebral bodies of the coccyx.
•It acts as an anchor for the spinal cord and meninges.
•Dura Mater
•most external of the meninges.
• It extends from the foramen magnum to the filum terminale,
• separated from the walls of the vertebral canal by the epidural space.
• This space contains some loose connective tissue, and the internal
vertebral venous plexus.
•As the spinal nerves exit the vertebral canal, they pierce the dura mater,
temporarily passing in the epidural space.
•In doing so, the dura mater surrounds the nerve root, and fuses with the
outer connective tissue covering of the nerve, the epineurium.

45. Arachnoid Mater
•The spinal arachnoid mater is a delicate membrane, located between the
dura mater and the pia mater.
•It is separated from the latter by the subarachnoid space, which contains
cerebrospinal fluid.
•Distal to the conus medullaris, the subarachnoid space expands, forming
the lumbar cistern.
•This space accessed during a lumbar puncture (to obtain CSF fluid) and
spinal anaesthesia.

46. Pia Mater
•The spinal pia mater is the innermost of the meninges.
•It is a thin membrane that covers the spinal cord, nerve roots and their
blood vessels.
•Inferiorly, the spinal pia mater fuses with the filum terminale.
•Between the nerve roots, the pia mater thickens to form the denticulate
ligaments.
•These ligaments attach to the dura mater – suspending the spinal cord in
the vertebral canal.

47. THANK YOU