Filum terminale
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The filum terminale ('terminal thread') is a delicate strand of fibrous tissue, about 20 cm in length, extending inferiorly from the apex of the conus medullaris to attach onto the coccyx.[1][2] The filum terminale acts to anchor the spinal cord and spinal meninges inferiorly.[3]
The upper portion of the filum terminale is formed by spinal pia mater within a dilated dural sac, while the lower portion is formed by both pia and dura mater (with the outer dural layer closely adhering to the inner pial component).
Anatomy
The proximal/superior partTemplate:Dashthe filum terminale internum or pial part of terminal filum[3]Template:Dashmeasures 15 cm in length and extends as far as the inferior border[1] of the second sacral vertebra (S2)[1][2] (the inferior limit sacral canal[2]). It is composed of the vestiges of neural tissue, connective tissue, and neuroglial tissue lined by pia mater.[3] It is contained within a tubular sheath of the dura mater and is surrounded by the nerves of the cauda equina (from which it can be easily recognized by its blueish-white color).[1]
The inferior/distal partTemplate:Dashthe filum terminale externum, dural part of terminal filum, or coccygeal ligament - is formed as the filum terminale internum reaches the inferior extremity of the dural sac; henceforth, the filum terminale becomes invested by a layer of dura mater.[1]
The filum terminale ultimately terminates inferiorly by attaching to the dorsum of the coccyx[3][2] at the first coccygeal segment,[1] flaring out[4] to blend with the coccygeal periosteum.[2]
Relations
The filum terminale is situated centrally[2] amid the spinal nerve roots of the cauda equina[3][2] (but is not itself a part of the cauda equina[2]).
The inferior-most spinal nerve, the coccygeal nerve, leaves the spinal cord at the level of the conus medullaris via respective vertebrae through their intervertebral foramina, superior to the filum terminale. However, adhering to the outer surface of the filum terminale are a few strands of nerve fibres which probably represent rudimentary second and third coccygeal nerves.[5]
The central canal of the spinal cord extends inferiorly into the superior part of the filum terminale.[1][2]
Development
The filum terminale is the vestigial remnant of the caudal portion of the spinal cord which forms a tail-like caudal eminence in the embryo.[3]
Additional images
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Spinal cord. Spinal membranes and nerve roots. Deep dissection. Posterior view.
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Spinal cord. Spinal membranes and nerve roots. Deep dissection. Posterior view.
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Spinal cord. Spinal membranes and nerve roots. Deep dissection. Posterior view.
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Spinal cord. Spinal membranes and nerve roots. Deep dissection. Posterior view.
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Spinal cord. Spinal membranes and nerve roots. Deep dissection. Posterior view.
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Spinal cord. Spinal membranes and nerve roots. Deep dissection. Posterior view.
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Spinal cord. Spinal membranes and nerve roots. Deep dissection. Posterior view.
References
Public domain This article incorporates text in the public domain from Template:Wikidatathe 20th edition of Gray's Anatomy (1918) Template:Main other
- Martini, F. Timmons, M. and Tallitsch, R. Human Anatomy. 5th ed. San Francisco: Pearson/Benjamin Cummings, 2006.
External links
- Template:LoyolaMedEd
- lesson6spinalcord&coverings at The Anatomy Lesson by Wesley Norman (Georgetown University)
- Anatomy photo:02:08-0104 at the SUNY Downstate Medical Center - "Vertebral Canal and Spinal Cord: Regions of the Spinal Cord"
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