General Arrangement and Surfaces
Anatomically, the spinal cord is housed within the vertebral canal. This natural osseous enclosure reliably protects the neural tissue.
Upon detailed examination, anatomists distinguish exactly 4 surfaces:
- Anterior;
- Posterior;
- Two lateral.
This spatial division helps to precisely describe the exit of nerve roots and the course of ascending and descending tracts.
Skeletotopic Borders
For clinical practice, it is crucial to understand where the spinal cord begins and where it ends. Its borders have clear reference points relative to bony structures (skeletotopy).
Superior Border There is no sharp anatomical boundary between the spinal cord and the brain; it transitions smoothly into the medulla oblongata. However, skeletotopically, this border is defined precisely: it corresponds to the level between the inferior margin of the foramen magnum and the superior margin of the atlas (C1 vertebra).
Inferior Border The inferior border varies with age due to the differential growth rates of the spinal cord and the vertebral column during development:
- In adults, the spinal cord terminates relatively high—at the level of the L1–L2 vertebrae.
- In newborns, the spinal cord is relatively longer and reaches the level of the L3 vertebra.
Conus Medullaris and Filum Terminale
In its inferior portion, the spinal cord tapers to form the conus medullaris.
Arising from the apex of the conus medullaris is a delicate fibrous cord known as the filum terminale. It plays a key role in anchoring the spinal cord within the vertebral canal, preventing undue displacement.
The filum terminale is structurally divided into two parts:
- Filum terminale internum (internal terminal fiber);
- Filum terminale externum (external terminal fiber) — this part is a derivative of the dura mater.
Notably, the filum terminale is not merely an empty ligament; it is accompanied by blood vessels and may contain rudimentary coccygeal nerve roots.