They are composed of three layers (outer to inner)
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.
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
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.
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.
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
- cerebrospinal fluid (CSF)
- arteries: radicular / segmental medullary and spinal
- 1. Last's anatomy, regional and applied. Churchill Livingstone. ISBN:044304662X. Read it at Google Books - Find it at Amazon
- 2. Dalley AF, Agur AM. Clinically Oriented Anatomy, Sixth Edition. Lippincott Williams & Wilkins. ISBN:1605476528. Read it at Google Books - Find it at Amazon
- 3. Gray's Anatomy. Churchill Livingstone. (2011) ISBN:0443066841. Read it at Google Books - Find it at Amazon
- 4. Snell RS. Clinical Anatomy By Regions International. LWW. ISBN:1451110324. Read it at Google Books - Find it at Amazon
- 5. Krings T. Vascular malformations of the spine and spinal cord: anatomy, classification, treatment. Clin Neuroradiol. 2010;20 (1): 5-24.
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