Pyramid of medulla oblongata

The pyramid of medulla oblongata is a paired, ridge-like white matter structure located on the ventral surface of the medulla oblongata. These prominent formations are part of the pyramidal motor pathways, comprising the corticospinal and corticobulbar tracts.

Each pyramid flanks the anterior median fissure, with its lateral boundary marked by the anterolateral (pre-olivary) sulcus, from which the hypoglossal nerve emerges. Lateral to this sulcus lies the olive, a distinctive bulge. The corticospinal tracts, located within each pyramid, transmit motor signals originating from the precentral gyrus via the internal capsule, pons, and medulla. Motor pathways not passing through the pyramids are classified as extrapyramidal tracts. At the caudal end of the pyramids, corticospinal axons decussate at the lower anterior part of the anterior median fissure, forming the lateral corticospinal tract. This decussation is responsible for the contralateral control of voluntary movements.