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 ''Conus'' is a genus of predatory sea snails, or cone snails, marine gastropod mollusks in the family Conidae.Bouchet, P.; Gofas, S. (2015). Conus Linnaeus, 1758. In: MolluscaBase (2015). Accessed through: World Register of Marine Species a ...

. It is one of the modifications of pia mater. It gives longitudinal support to the

spinal cord The spinal cord is a long, thin, tubular structure made up of nervous tissue, which extends from the medulla oblongata in the brainstem to the lumbar region of the vertebral column (backbone). The backbone encloses the central canal of the spi ...

and consists of two parts: * The upper part, or filum terminale internum, is about 15 cm long and reaches as far as the lower border of the second sacral vertebra. It is continuous above with the pia mater and contained within a tubular sheath of the

dura mater In neuroanatomy, dura mater is a thick membrane made of dense irregular connective tissue that surrounds the brain and spinal cord. It is the outermost of the three layers of membrane called the meninges that protect the central nervous system. T ...

. In addition, it is surrounded by the nerves forming the

cauda equina The cauda equina () is a bundle of spinal nerves and spinal nerve rootlets, consisting of the second through fifth lumbar nerve pairs, the first through fifth sacral nerve pairs, and the coccygeal nerve, all of which arise from the lumbar enla ...

, from which it can be easily recognized by its bluish-white color. * The lower part, or filum terminale externum, closely adheres to the dura mater. It extends downward from the apex of the tubular sheath and is attached to the back of the first segment of the

coccyx The coccyx ( : coccyges or coccyxes), commonly referred to as the tailbone, is the final segment of the vertebral column in all apes, and analogous structures in certain other mammals such as horses. In tailless primates (e.g. humans and other ...

in a structure sometimes referred to as the ''coccygeal ligament''. The most inferior of the spinal nerves, the

coccygeal nerve A spinal nerve is a mixed nerve, which carries motor, sensory, and autonomic signals between the spinal cord and the body. In the human body there are 31 pairs of spinal nerves, one on each side of the vertebral column. These are grouped into the ...

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 An axon (from Greek ἄξων ''áxōn'', axis), or nerve fiber (or nerve fibre: see spelling differences), is a long, slender projection of a nerve cell, or neuron, in vertebrates, that typically conducts electrical impulses known as action po ...

which probably represent rudimentary second and third coccygeal nerves. Furthermore, the

central canal The central canal (also known as spinal foramen or ependymal canal) is the cerebrospinal fluid-filled space that runs through the spinal cord. The central canal lies below and is connected to the ventricular system of the brain, from which it r ...

of the spinal cord extends 5 to 6 cm beyond the conus medullaris, downward into the filum terminale.

Additional Images

File:Slide3dsdd.GIF, Spinal cord. Spinal membranes and nerve roots.Deep dissection. Posterior view. File:Slide5sese.GIF, Spinal cord. Spinal membranes and nerve roots.Deep dissection. Posterior view. File:Slide6drdr.GIF, Spinal cord. Spinal membranes and nerve roots.Deep dissection. Posterior view. File:Slide4rer.JPG, Spinal cord. Spinal membranes and nerve roots.Deep dissection. Posterior view. File:Slide5rer.JPG, Spinal cord. Spinal membranes and nerve roots.Deep dissection. Posterior view. File:Slide6rer.JPG, Spinal cord. Spinal membranes and nerve roots.Deep dissection. Posterior view. File:Slide7feer.JPG, Spinal cord. Spinal membranes and nerve roots.Deep dissection. Posterior view.

References

* Martini, F. Timmons, M. and Tallitsch, R. ''Human Anatomy''. 5th ed. San Francisco: Pearson/Benjamin Cummings, 2006.

External links

* * * - "Vertebral Canal and Spinal Cord: Regions of the Spinal Cord" * {{Authority control Meninges