The meninges of the brain I

A. Dura mater (2 layers) Endosteal layer Meningeal layer Covers the inner surface of the skull bones...

A. Dura mater (2 layers)

Endosteal layer	Meningeal layer
Covers the inner surface of the skull bones Doesn’t continue with the dura mater of the spinal cord at the foramen magnum At all the foramina of the skull, it becomes continues with the periosteum	It’s the dura mater proper Continue with the dura mater of the spinal cord at the foramen magnum It covers the cranial nerves which are passing through skull foramina

The arrangement of the meninges as the cranial nerve passes through foramina in skull

Falx cerebri & the tentorium cerebelli

Superior view of the Diaphragma sellae & tentorium cerebelli






Dural septa


1) The Meningeal layer forms 4 septa which divide the cranial cavity into spaces that lodge the subdivisions of the brain

2) The function of these septa is to restrict the displacement of the brain when the head is moved

Dural septum	Description	Sinuses
Falx cerebri (Vertical)	Lies in the midline of between 2 cerebral hemispheres Sickle shaped Posterior part blends with the tentorium cerebelli	Superior sagittal sinus runs in the upper fixed margin Inferior sagittal sinus runs in the lower free margin Straight sinus runs along the attachment to the tentorium cerebelli
Tentorium cerebelli (Horizontal)	Forms the roof of the posterior cranial fossa Crescent shaped  Covers the upper surface of the cerebellum & supports the occipital lobes of the cerebral hemispheres There’s a gap called tentorial notch, for the passage of the midbrain	Superior petrosal sinus runs along its attachment to the petrous bone Transverse sinus runs along its attachment to the occipital bone
Falx cerebelli	Attached to the lower surface of the tentorium Sickle shaped It lies between the 2 cerebellar hemispheres	Posterior fix margin contains the occipital sinus
Diaphragma sellae	There’s a small opening in the center which allows passage of the stalk of the pituitary Circular fold

Dural nerve supply

1) Dura has numerous sensory nerve endings that are sensitive to stretching (Can cause headache)

2) Stimulation of the V nerve (TGN) above the tentorium cerebelli : Referred pain to an area of skin on the same side of the head

3) Stimulation of the V nerve (TGN) below the tentorium cerebelli : Referred pain to the back of the neck & back of the scalp (Along the distribution of the greater occipital nerve)


Dural arterial supply

1) Most important artery is the middle cerebral artery

2) It lies between the meningeal & endosteal layers of the dura mater

3) It can be damaged in head injuries & produce hematomas

Epidural hemorrhage

Subdural hemorrhage

Dural venous sinuses

1) The venous sinuses are situated between the layers of the dura mater

2) Functions of the venous sinuses

1. Receive blood from the brain through the cerebral veins (Then blood drains into internal jugular veins)
2. Receive CSF from the SAS through the arachnoid villi

3) Structure of the sinuses

1. Lined by the endothelium
2. Walls don’t have any muscles
3. No valves

4) Emissary veins (Don’t have valves) connect the sinuses with the diploic veins of the skull & with the veins of the scalp