Meninges
Definition
Meninges = membranes covering the brain and spinal cord
They are
o Duramater
o Arachnoid mater
o Pia mater
Duramater
o Two layers of dense fibrous tissue
o Outer layer takes the place of periosteum on the inner surface of the skull
o Inner layer covers the brain
o Forms a partition between the two cerebral hemispheres called the falx cerebri
o Between the cerebellar hemispheres - falx cerebelli
o Between the cerebrum and cerebellum - tentorium cerebelli
o Venous blood from the brain flows through the venous sinuses between the layers of dura mater.
o Falx cerebri forms the superior sagittal sinus
o Tentorium cerebelli forms the straight and and transverse sinuses
Spinal Dura mater
o Foms a loose sheath around the spinal cord
o Extends from the foramen magnum to the S2 vertebra
o Then it invests the filum terminale
o Fuses with the periosteum of the coccyx
o It is separated from the periosteum of the vertebrae and ligaments within the neural canal by the epidural space.
Arachnoid mater
o Middle layer of the three membranes covering the brain and spinal cord
o Separated from the dura mater by the subdural space and from the pia mater by the subarachnoid space
o Subarachnoid space contains the cerebrospinal fluid
o Covers the spinal cord also and ends by merging with the dura mater at the level of S2
Pia mater
o Inner most layer of the meninges
o Fine connective tissue
o Contains minute blood vessels
o Closely invests the brain
o Completely covers the convolutions
o Dips into fissures
o Invests the spinal cord
o Beyond the end of the spinal cord continues as the filum terminale
o Pierces arachnoid mater and with dura mater fuses with periosteum of the coccyx
Applied anatomy :
o epidural space - epidural anaesthesia
o Subarachnoid space of the spinal canal - spinal anaesthesia
