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The Spine Quiz
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In an adult, what is the bundle of descending spinal nerve roots below the end of the spinal cord called?
- A Lumbar enlargement You picked ✕
- B Denticulate ligaments You picked ✕
- C Conus medullaris You picked ✕
- D Filum terminale You picked ✕
- E Cauda equina You picked ✓
Correct!
Incorrect
The answer is E: Cauda equina
Explanation
Why E is correct
See Structure of the Vertebrae. Option E is correct: the cauda equina (Latin for "horse's tail") is the bundle of nerve roots that carries on down the vertebral canal after the spinal cord has ended. The cord stops growing in infancy while the bony spine keeps growing, so in an adult the cord ends only around the level of the first or second lumbar vertebra. The lower nerve roots therefore have to travel a long way down inside the canal before they reach their own exit holes (the intervertebral foramina), and together they look like a horse's tail. The tapered tip of the cord from which they stream is the conus medullaris. The cauda equina carries the lumbar, sacral and coccygeal roots, and compression of these roots produces the group of problems called cauda equina syndrome.
- Cauda equina: the bundle of nerve roots that carries on down the vertebral canal after the spinal cord has ended.
- Level: in an adult the cord ends around the first or second lumbar vertebra.
- Conus medullaris: the tapered tip of the cord from which the roots stream.
Why the other options are incorrect
- A. Lumbar enlargement: The lumbar enlargement is a widening of the spinal cord itself between about T11 and L1, where the nerves for the lower limb arise. It is part of the cord and sits above the conus medullaris. Your answer
- B. Denticulate ligaments: The denticulate ligaments are thickened sheets of pia mater (the innermost membrane on the cord) that attach to the dura mater and hold the cord in place. They are anchoring ligaments, not nerve roots. Your answer
- C. Conus medullaris: The conus medullaris is the tapered lower tip of the spinal cord itself, at about the L1 to L2 level. The nerve roots stream down from it, so it is the end of the cord rather than the bundle of roots. Your answer
- D. Filum terminale: The filum terminale is a thin strand of fibrous tissue formed by the meninges (the protective membranes around the cord). It anchors the cord and meninges to the coccyx and does not carry nerve roots. Your answer
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1
Which anatomical feature is characteristic of typical cervical vertebrae?
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2
Which ligament runs along the tips of the spinous processes in the thoracic and lumbar spine and helps to resist excessive forward flexion?
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