Editing Pyramidal tracts (section)

{{Short description|The corticobulbar tract and the corticospinal tract}}
{{Infobox tract
| Name            = Pyramidal tracts
| Latin           =tractus pyramidalis<br />tractus corticospinalis 
| Image           = Gray684.png
| Caption         = Deep dissection of brain-stem. Lateral view. ("pyramidal tract" visible in red, and "pyramidal decussation" labeled at lower right.)
| Image2          = Spinal cord tracts - English.svg
| Caption2        = [[Spinal cord tracts]], with ''pyramidal tracts'' labeled at upper left
| IsPartOf        =
| Components      =
| Artery          =
| Vein            =
| From = [[Cerebral cortex]] 
| To = [[Spinal cord]] (''corticospinal'') or [[brainstem]] (''corticobulbar'')
| Decussation = Many fibres in the [[medullary pyramids]] 
|System=|Function=}}

The '''pyramidal tracts''' include both the [[corticobulbar tract]] and the [[corticospinal tract]]. These are aggregations of [[efferent nerve fiber]]s from the [[upper motor neuron]]s that travel from the [[cerebral cortex]] and terminate either in the [[brainstem]] (''corticobulbar'') or [[spinal cord]] (''corticospinal'') and are involved in the [[Motor control|control of motor functions]] of the body.

The corticobulbar tract conducts [[action potential|impulses]] from the [[brain]] to the [[cranial nerve]]s.<ref>Chapter 9 of "Principles of Physiology" (3rd edition) by Robert M. Berne and Mathew N. Levy. Published by Mosby, Inc. (2000) {{ISBN|0-323-00813-5}}.</ref> These nerves control the muscles of the face and neck and are involved in facial expression, mastication, swallowing, and other motor functions.

The [[corticospinal tract]] conducts impulses from the brain to the spinal cord. It is made up of a [[lateral corticospinal tract|lateral]] and [[anterior corticospinal tract|anterior tract]]. The corticospinal tract is involved in voluntary movement. The majority of fibres of the corticospinal tract [[medullary pyramids#Decussation|cross over]] in the [[medulla oblongata]], resulting in muscles being controlled by the opposite side of the brain. The corticospinal tract contains the [[axon]]s of the pyramidal cells, the largest of which are the [[Betz cell]]s, located in the [[primary motor cortex]].

The pyramidal tracts are named because they pass through the [[Medullary pyramids|pyramids]] of the [[medulla oblongata]]. The corticospinal fibers converge to a point when descending from the [[internal capsule]] to the brain stem from multiple directions, giving the impression of an inverted pyramid. Involvement of the pyramidal tract at any level leads to [[pyramidal signs]].

The [[myelin]]ation of the pyramidal fibres is incomplete at birth and gradually progresses in cranio-caudal direction and thereby progressively [[Child development stages#Motor, speech, vision and hearing|gaining functionality]]. Most of the myelination is complete by two years of age and thereafter it progresses very slowly in cranio-caudal direction up to twelve years of age.