The spinal meninges (singular: meninx) are contained within the spinal canal and encase the spinal cord, spinal nerve roots and the cauda equina.
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Gross anatomy
They are composed of three layers (outer to inner)
dura mater (also known as theca or pachymeninx)
Collectively, the arachnoid and pia mater together are known as the leptomeninges. There are three potential spaces, which are the epidural, subdural and subarachnoid spaces.
Dura mater
The dura is an extension of the dura mater from the posterior cranial fossa. It forms a spinal dural sac, which spans from the foramen magnum to the level of S2, where it attaches to the coccyx by the filum terminale.
The dura lies free apart from attachments to the tectorial membrane and posterior longitudinal ligament on the body of the axis vertebra. The dura mater is also stabilized by anterior and posterior spinal nerve roots, which pierce it segmentally and give lateral projections after they exit. Innervation is from the recurrent meningeal nerves.
It sits within the spinal canal within a layer of fat containing the internal vertebral venous plexus.
Also see separate article: spinal dura mater .
Arachnoid mater
The arachnoid mater is separated from the dura by a thin film of lymph, the potential subdural space. It is a thin avascular membrane lining the dural sac and nerve root sheaths. A posterior median septum lies over the spinal cord, formed by web-like arachnoid processes. Below the spinal cord, the arachnoid mater is a thin membrane at the cauda equina.
Also see separate article: spinal arachnoid mater.
Pia mater
The pia invests the spinal cord and the spinal nerve roots, blending with the epineurium. It extends bilaterally as paired denticulate ligaments, a series of triangular processes fixed to the dura mater. Below the conus medullaris, it continues as the filum terminale.
Also see separate article: spinal pia mater.
Epidural space
The space between the dura mater and the periosteum and ligaments of the vertebral canal. Superiorly bounded by the fusion of the dura with the foramen magnum and inferiorly bounded by the posterior sacrococcygeal ligament that closes the sacral hiatus. It contains:
fat
spinal nerve roots below S2
Subarachnoid space
The interval between the arachnoid membrane and pia mater. This interval is particularly large in the lumbar region, forming the lumbar cistern. The subarachnoid space contains:
arachnoid trabeculae
arteries: radicular/segmental medullary and spinal
veins
History and etymology
The word meninges, is the plural of meninx, from the Classical Greek μηνιγξ (transliteration: meninx) literally meaning membrane 6.