They are composed of three layers (outer to inner)
Collectively the arachnoid and pia mater together are known as the leptomeninges. There are two potential spaces: epidural and subdural.
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 stabilised 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.
The arachnoid mater is separated from the dura by a thin film of lymph. 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 caudal equina.
The pia invests the spinal cord and the spinal nerve roots, blending in with the epineurium. It is continuous with the ligamentum denticulatum, which at its lateral border has a series of triangular processed that are fixed to the dura mater. Below the conus medullaris, it continues as the filium terminale.
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 the posterior sacrococcygeal ligament that closes the sacral hiatus. It contains:
- internal vertebral venous plexus
- spinal nerve roots below S2
This is a thin cell layer between the closely apposed arachnoid and pia mater. It contains:
- arachnoid trabeculae
- arteries: radicular, segmental, medullary and spinal
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- spinal canal
- cervical spine
- thoracic spine
- lumbar spine
- vertebral body
- neural arch
- transitional vertebrae
- ossification centres
- intervertebral disc
- anterior longitudinal ligament
- posterior longitudinal ligament
- posterior ligamentous complex
- cervical spine ligaments
- iliolumbar ligament
- musculature of the vertebral column
- muscles of the neck
- muscles of the back
- gross anatomy
white matter tracts
- anterolateral columns
- lateral columns
- dorsal columns
- gray matter
- nerve root
- spinal meninges and spaces
- functional anatomy
- spinal cord blood supply