Lateral fasciculus proprius

At a glance

English

Lateral fasciculus proprius

Latin (TA2)

Fasciculus proprius lateralis

System

Nerve

Region

Whole body

Side

Single, on the midline

About the lateral fasciculus proprius

The lateral fasciculus proprius belongs to the proper, or propriospinal, system of the spinal cord. This system has three parts, anterior, lateral and posterior, which together make a thin coat of white matter clinging to the grey matter. The fibres are short; they rise or fall over a few segments, on the same or the opposite side, and then turn back into the grey substance. Some collaterals of entering posterior root fibres travel with them.

In the lateral funiculus the bundle occupies the deepest zone, between the grey matter and the long tracts such as the lateral corticospinal, rubrospinal and spinocerebellar pathways. Older descriptions call it the rest of the lateral column once the named long tracts are subtracted. Towards the front it merges with the anterior fasciculus proprius without a sharp boundary.

Most of its axons arise from interneurons in the grey matter of the intermediate zone and the bases of the horns. After running for a short or longer distance they pass back into the grey substance and branch there, ending on interneurons and motor neurons of other segments. A share of fibres does not stop in the cord but continues upwards into the brainstem, where it joins the medial longitudinal fasciculus.

These connections tie spinal segments together. They allow a reflex started at one level to recruit motor neurons at several others, so that, for example, limb and trunk muscles act in a coordinated pattern. Propriospinal neurons also relay part of the descending traffic from the brain, which gives the system a role in posture, locomotion and the coupling of upper and lower limbs during walking. Because the bundle lies so close to the grey matter it is usually damaged together with it, as in central cord lesions.

Course and supply

Supplies

Connects neighbouring spinal segments so that reflexes spread over several levels and limb and trunk muscles act together.

Blood supply

Lies next to the grey matter in the territory of the anterior spinal artery and its sulcal branches.