|Anterior external arcuate fibers|
|Diagram showing the course of the arcuate fibers. (Testut.) 1. Medulla oblongata anterior surface. 2. Anterior median fissure. 3. Fourth ventricle. 4. Inferior olivary nucleus, with the accessory olivary nuclei. 5. Gracile nucleus. 6. Cuneate nucleus. 7. Trigeminal. 8. Inferior peduncles, seen from in front. 9. Posterior external arcuate fibers. 10. Anterior external arcuate fibers. 11. Internal arcuate fibers. 12. Peduncle of inferior olivary nucleus. 13. Nucleus arcuatus. 14. Vagus. 15. Hypoglossal.|
|Latin||fibrae arcuatae externae anteriores|
|Gray's||subject #187 782|
|Section of the medulla oblongata at about the middle of the olive. (Arcuate fibers labeled at center right.)|
The anterior external arcuate fibers (ventral external arcuate fibers) vary as to their prominence in different cases: in some they form an almost continuous layer covering the pyramid and olive, while in others they are barely visible on the surface.
Most of them reach the surface by way of the anterior median fissure, and arch backward over the pyramid.
They thus connect the cerebellum with the gracile and cuneate nuclei of the opposite side.
As the fibers arch across the pyramid, they enclose a small nucleus which lies in front of and medial to the pyramid.
This is named the nucleus arcuatus, and is serially continuous above with the nuclei pontis in the pons; it contains small fusiform cells, around which some of the arcuate fibers end, and from which others arise.
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