The brain is the most important as well as a delicate organ in our system which needs protection.
the brain is protected by 3 layers of different membrane
Boney covering of cranium
Meninges
Cerebrospinal fluid
Meninges are three membranous covering of the brain that lies below the skull
the first layer is the outer dura mater, also called the pachymenix, followed by the middle arachnoid mater and the inner pia mater.
Dura Mater
the cerebral dura mater is the outermost thickest and toughest membrane of the meninges.
the dura mater contains 2 layers
outer or endosteal layer
inner or meningeal layer
Endosteal layer
It serves as an endosteum of the skull.
It continues with:
periosteum lining outside the skull
the periosteal lining of orbit
pericranium through sutures
-acts as a sheath for cranial nerves.
-Dura mater fuses with the epicranium and continues its course with the sclera.
-The outer surface of the dura mater is adherent to the inner surface of the skull through some vascular process.
Meningeal layer
The meningeal layer of the dura mater is folded to form a partition that divides the cranial cavity into compartments
tentorium cerebelli
falx cerebri
Diaphragma sellae
Falx cerebelli
tentorial notch
Falx cerebri
occupies the median longitudinal fissure between two cerebral hemispheres.
the anterior end is narrow and attached to crista Gallia.
the posterior end is broad and attached to the tentorium cerebelli.
it has 2 margins:
Upper margin
attached to the sagittal sulcus
the superior sagittal sins lie in the upper margin.
the superior sagittal sinus drains the superior cerebral veins.
Lower Margin
the lower margin is convex and free
the inferior sagittal sinus runs along the lower margin.
it drains blood from the flax and the medial surface of cerebrum.
Tentorium cerebelli
forms the roof of the posterior cranial fossa
separates the cerebellum from the occipital lobes of cerebrum
divides the cranial cavity into supratentorial and infratentorial compartments.
it has two margins:
FREE MARGIN
'U' shaped
attached to the anterior clinoid process
the free margin forms the tentorial notch
tentorial notch is occupied by the midbrain and the anterior margin of superior vena cava
ATTACHED MARGIN
Attached to the transverse sulci of occipital bone and the posteroinferior angle of parietal bone in the posterolateral
Attached to the superior border of petrous temporal bone in the anterolateral region.
contains the transverse and the superior petrosal venous sinus.
free and attached margins of tentorium cerebelli cross at the apex of temporal bone to form a triangular area which is the posterior part of the cavernous sinus
the tentorium cerebelli has two surfaces
SUPERIOR SURFACE
convex and slopes to either side of the median plane
gives attachment to falx cerebelli
the superior surface is related to the occipital lobes of the cerebellum
INFERIOR SURFACE
concave and fits superior surface
falx cerebelli
Sickel-shaped fold of dura mater projecting in the inferior surface of tentorium cerebelli.
the base of the sickle is attached to the inferior surface of tentorium cerebelli and the apex is divided into two parts
anterior margin
concave and free
posterior margin
attached to the internal occipital crest
encloses the occipital sinus
Diaphragma sellae
small fold present near the hypophyseal fossa.
anteriorly attached to tuberculum selae and posteriorly attached to the dorsum sellae
the stalk of hypophysis cerebri passes through the central aperture of dorsum sellae
BLOOD SUPPLY
the outer layer is rich and vascular whereas the inner layer needs more blood supply
supratentorial space is supplied by the middle meningeal artery
anterior cranial fossa and the dural lining is supplied by the meningeal branch of the anterior ethmoidal artery, posterior ethmoidal artery, and the ophthalmic artery
NERVE SUPPLY
the dura mater of the vault has a few sensory nerves from the ophthalmic division of a trigeminal nerve
the dural of the floor has a rich nerve supply
anterior cranial fossa - supplied by the anterior ethmoidal nerve and the maxillary nerve
middle cranial fossa - the maxillary nerve in the anterior half
- trigeminal ganlion in the posterior half
posterior cranial fossa - c1, c2, c3 recurrent branches and partly by the meningeal branch of the vagus nerve
reference - B.D chaurasias, Greys anatomy for students
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