Projection fibers

The projection fibers consist of efferent and afferent fibers uniting the cortex with the lower parts of the brain and with the spinal cord.

Efferent

The principal efferent strands are:

• (1) the motor tract, occupying the genu and anterior two-thirds of the occipital part of the internal capsule, and consisting of
  • (a) the geniculate fibers, which decussate and end in the motor nuclei of the cranial nerves of the opposite side; and
  • (b) the cerebrospinal fibers, which are prolonged through the pyramid of the medulla oblongata into the medulla spinalis:
• (2) the corticopontine fibers, ending in the nuclei pontis.

Afferent

The chief afferent fibers are:

• (1) those of the lemniscus which are not interrupted in the thalamus;
• (2) those of the superior cerebellar peduncle which are not interrupted in the red nucleus and thalamus;
• (3) numerous fibers arising within the thalamus, and passing through its stalks to the different parts of the cortex ;
• (4) optic and acoustic fibers, the former passing to the occipital, the latter to the temporal lobe.

External links

• Diagram at kennedykrieger.org
• Overview at mch.com

This article was originally based on an entry from a public domain edition of Gray's Anatomy. As such, some of the information contained within it may be outdated.

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