pyramidal tract

anatomy

Also known as: medullary pyramid

Written by

The Information Architects of Encyclopaedia Britannica

Last updated

July 13, 2026

Quick Summary

The pyramidal tract, also known as the corticospinal tract, is a crucial part of the motor system in the human nervous system. It consists of motor fibers that originate in the cerebral cortex and descend through the brainstem, specifically the medulla oblongata, before continuing into the spinal cord.123

The primary function of the pyramidal tract is to control skilled, voluntary movements. Most of these fibers (80-90%) cross over to the opposite side of the body in the lower medulla, which is why damage to one side of the brain can affect the opposite side of the body. The term "extrapyramidal" refers to nerve tracts and systems outside of the pyramidal tracts, which are involved in different aspects of motor control.234

Summary created from Britannica articles using AI. AI can make mistakes, so verify using Britannica articles.

4 Britannica Sources

Ask Britannica AI about this topic

Britannica doesn't have a full article on this topic, so we've curated a list of our relevant coverage.

human nervous system
Corticospinal tract
…the medulla, known as the medullary pyramids. In the lower medulla about 90 percent of the fibers of the corticospinal tract decussate and descend in the dorsolateral funiculus of the spinal cord. Of the fibers that do not cross in the medulla, approximately 8 percent cross in cervical spinal segments.…
Read More
…the medulla, known as the medullary pyramids. In the lower medulla about 90 percent of the fibers of the corticospinal tract decussate and descend in the dorsolateral funiculus of the spinal cord. Of the fibers that do not cross in the medulla, approximately 8 percent cross in cervical spinal segments.…
Read More