All parts of the brain › Spinal cord

Where is the spinal cord?

The spinal cord starts where the medulla oblongata, the bottom of the brainstem, ends: at the foramen magnum, the large opening in the base of the skull. From there it runs down inside the spinal canal of the vertebrae and ends, in adults, between the first and second lumbar vertebrae in the lower back. [1][2]

The model shows only its top part, where it joins the medulla oblongata, and draws it as its central canal (BodyParts3D part FJ1737), the thin fluid channel down its middle; the canal runs up inside the lower medulla and reaches about 6 mm below it. [3]

The 3D brain needs JavaScript. The text below still says where the spinal cord is and what it does.

Slice

Opens cut by a side (sagittal) slice through the spinal cord. Drag to turn, pinch or scroll to zoom, tap any part to name it; .

Next to it, each lit on its own page: medulla oblongata, brainstem, fourth ventricle.

Where it is

It continues the medulla oblongata down from the foramen magnum, passes into the spinal canal at the start of the neck (cervical) vertebrae, and runs inside the canal formed by the stacked vertebrae. [1][4]
In adults it ends between the first and second lumbar vertebrae, where it tapers into the cone-shaped conus medullaris; below that the nerve roots continue down as a bundle called the cauda equina (“horse’s tail”). [1][5]
Down its middle runs the central canal, a narrow channel of cerebrospinal fluid that is continuous above with the fourth ventricle of the brain. [6]

What it does

It carries signals both ways between the brain and the body: sensory tracts run up it to the brain and motor tracts run down it to the muscles. [1][4]
It holds its own circuits, such as reflex arcs that act on a stimulus before the brain is involved, and networks that set the rhythm of walking. [1][7]
31 pairs of spinal nerves leave it through the gaps between the vertebrae: 8 cervical, 12 thoracic, 5 lumbar, 5 sacral and 1 coccygeal. [1][8]

Inside it

In cross-section, butterfly- or H-shaped grey matter (nerve cell bodies) sits in the middle, surrounded by white matter (the long fibre tracts) — the reverse of the cerebrum, where grey matter is on the outside. [1][4]

Other names

Medulla spinalis (Latin). With the brain it makes up the central nervous system. [1]

Size

In a living adult (not this model) it is about 45 cm long in men and 43 cm in women, and about 13 mm across at its thickest, in the neck and lower back, narrowing to about 6.4 mm in the chest region. [1]
On this model the spinal cord (central canal) measures about 13 mm front to back, 36 mm top to bottom and 2 mm side to side (the box it fits in, not its volume). [3]
Centre of the spinal cord (central canal) compared with the centre of the medulla oblongata: 13 mm further back, 20 mm lower; 24 mm apart in a straight line. [3]
Centre of the spinal cord (central canal) compared with the centre of the fourth ventricle: 6 mm further back, 34 mm lower; 35 mm apart in a straight line. [3]

Sources

Facts describe anatomy and normal function only. The 3D model is the adult male BodyParts3D brain (credits and licence); real brains vary in size and shape, so its measurements describe one model, not anyone’s brain.