Gracile fasciculus
Fasciculus gracilis
The medial part of the posterior column of the spinal cord, carrying fine touch, vibration and position sense from the lower limb and lower trunk.
At a glance
- English
- Gracile fasciculus
- Latin (TA2)
- Fasciculus gracilis
- System
- Nerve
- Region
- Whole body
- Side
- Single, on the midline
About the gracile fasciculus
The gracile fasciculus, or tract of Goll, is the inner of the two bundles of the posterior (dorsal) column. It runs the full length of the cord, bordering the posterior median septum. On cross-section it is wedge-shaped: its broad base faces the back surface of the cord and its tip points forward towards the grey commissure behind the central canal. Below about the sixth thoracic segment it fills the whole posterior column; above that level the cuneate fasciculus is added lateral to it, separated by the posterior intermediate septum.
The bundle is made of the central processes of sensory cells in the spinal ganglia of the sacral, lumbar and lower thoracic segments. These enter through the posterior roots and turn upwards without crossing. Because new fibres are added at every level, the bundle grows steadily thicker as it rises towards the brain. Within it the fibres are arranged by body region, with those from the lowest segments lying most medially.
The fibres end in the gracile nucleus of the lower medulla, beneath the gracile tubercle at the lower end of the fourth ventricle. From there second-order neurons send internal arcuate fibres across the midline, and these ascend as the medial lemniscus to the ventral posterolateral nucleus of the thalamus and on to the leg area of the postcentral gyrus. The pathway carries discriminative touch, vibration and the sense of joint position for the leg and lower trunk.
Loss of this bundle leaves a person unsure where the feet are. Typical signs are a positive Romberg test, with swaying or falling when the eyes are shut, a stamping gait and lost vibration sense at the ankle. Such signs appear with posterior column disease, for example in vitamin B12 deficiency, and after injury to the back of the cord.
Course and supply
- Supplies
- Carries fine touch, vibration and joint position sense from the lower limb and lower trunk to the gracile nucleus of the medulla, on the same side.
- Blood supply
- Supplied by the paired posterior spinal arteries.
Anthromica
See the gracile fasciculus where it really sits, with every layer of the body around it.
- Every layer, one body. Peel from muscle to bone, nerve, vessel and organ, and turn it any way.
- English and Latin. Every structure named the way your exam names it.
- Quiz until it sticks. Short drills on the structures you keep missing.
Free to start. No card.
