The filum terminale is a delicate strand of fibrous tissue, about 20 cm. in length, proceeding downward from the apex of the conus medullaris

Conus medullaris

The conus medullaris is the terminal end of the spinal cord. It occurs near lumbar vertebral levels 1 and 2 . After the spinal cord tapers out, the spinal nerves continue as dangling nerve roots called cauda equina. This terminal nerve root tail is referred to as the filum terminale...

. It gives longitudinal support to the spinal cord

Spinal cord

The spinal cord is a long, thin, tubular bundle of nervous tissue and support cells that extends from the brain . The brain and spinal cord together make up the central nervous system...

 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
  Pia mater
  Pia mater often referred to as simply the pia, is the delicate innermost layer of the meninges, the membranes surrounding the brain and spinal cord. The word finds its roots in Latin, meaning literally "tender mother." The other two meningeal membranes are the dura mater and the arachnoid mater....
  
   and contained within a tubular sheath of the dura mater
  Dura mater
  The dura mater , or dura, is the outermost of the three layers of the meninges surrounding the brain and spinal cord. It is derived from Mesoderm. The other two meningeal layers are the pia mater and the arachnoid mater. The dura surrounds the brain and the spinal cord and is responsible for...
  
  . In addition, it is surrounded by the nerves forming the cauda equina
  Cauda equina
  The cauda equina is a structure within the lower end of the spinal column of most vertebrates, that consists of nerve roots and rootlets from above...
  
  , 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
  Coccyx
  The coccyx , commonly referred to as the tailbone, is the final segment of the vertebral column. Comprising three to five separate or fused vertebrae below the sacrum, it is attached to the sacrum by a fibrocartilaginous joint, the sacrococcygeal symphysis, which permits limited movement between...
  
   in a structure sometimes referred to as the coccygeal ligament.

The most inferior of the spinal nerves, the coccygeal nerve

Coccygeal nerve

-Structure:The coccygeal nerve is the 31st spinal nerve. It arises from the sacral plexus, and its ventral ramus helps form the coccygeal plexus. It does not divide into a medial and lateral branch...

 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

Central canal

For the engineering project, see Indiana Central Canal.The central canal is the cerebrospinal fluid-filled space that runs longitudinally through the length of the entire spinal cord. The central canal is contiguous with the ventricular system of the brain...

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

External links

- "Vertebral Canal and Spinal Cord: Regions of the Spinal Cord"