Filum terminale

Terminal filium
Cauda equina and filum terminale seen from behind. The dura mater has been opened and spread out, and the arachnoid has been removed. (Filum terminale labeled at center right.)
Sagittal section of vertebral canal to show the lower end of the medulla spinalis and the filum terminale.
Li, Lv. First and fifth lumbar vertebra.
SII Second sacral vertebra.
1. Dura mater.
2. Lower part of subarachnoid cavity.
3. Lower extremity of medulla spinalis.
4. Filum terminale internum.
5. Filum terminale externum.
6. Attachment of filum terminale to first segment of coccyx.
Latin filum terminale
Gray's subject #185 750

The filum terminale ("terminal thread"), is a delicate strand of fibrous tissue, about 20 cm. in length, proceeding downward from the apex of the conus medullaris. It gives longitudinal support to the spinal cord and consists of two parts:

The most inferior of the spinal nerves, the coccygeal nerve leaves the spinal cord at the level of the conus medullaris, superior to the filum terminale. However, adhering to the outer surface of the filum terminale are a few strands of nerve fibers which probably represent rudimentary second and third coccygeal nerves. Furthermore, the central canal of the spinal cord extends 5 to 6 cm beyond the conus medullaris, downward into the filum terminale.

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This article was originally based on an entry from a public domain edition of Gray's Anatomy. As such, some of the information contained within it may be outdated.