Decussation of pyramids

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Brain: Decussation of pyramids
Gray684.png
Deep dissection of brain-stem. Lateral view. ("pyramidal tract" visible in red, and "pyramidal decussation" labeled at lower right.)
Sobo 1909 675.png
Certain tracts of the brain, particularly of the corona radiata. The pyramidal tracts are red; the cerebropontile and central tegmental tracts are blue.
Latindecussatio pyramidum
Gray'ssubject #192, p.870
NeuroNameshier-796
NeuroLex IDbirnlex_1594
 
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Brain: Decussation of pyramids
Gray684.png
Deep dissection of brain-stem. Lateral view. ("pyramidal tract" visible in red, and "pyramidal decussation" labeled at lower right.)
Sobo 1909 675.png
Certain tracts of the brain, particularly of the corona radiata. The pyramidal tracts are red; the cerebropontile and central tegmental tracts are blue.
Latindecussatio pyramidum
Gray'ssubject #192, p.870
NeuroNameshier-796
NeuroLex IDbirnlex_1594

The two pyramids contain the motor fibers that pass from the brain to the medulla oblongata and medulla spinalis, corticobulbar and corticospinal fibers.

When these pyramidal fibers are traced downward, it is found that some three-fifths or more of them leave the pyramids in successive bundles, and decussate in the anterior median fissure of the medulla oblongata, forming what is termed the pyramidal decussation or motor decussation.

Having crossed the middle line, they pass down in the posterior part of the lateral funiculus as the lateral corticospinal tract.

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This article incorporates text from a public domain edition of Gray's Anatomy.