Morphological evaluation of the human pyramidal tract: tapering of axons.
It is generally accepted that nerve fiber conduction velocity is directly proportional to the fiber diameter under the condition, based on a supposition, that the transverse area of axons is normally maintained constant. Using an ideal preparation method for the purpose of axonal discrimination, we examined 43 human spinal cords after making transverse sections at the cervical, thoracic, lumbar and sacral levels and found a tapering of the axons in the lateral pyramidal tract, as the cross-sectional area of the pyramidal axons showed a definite decrease from the cervical to the sacral levels. Our results contradict the supposition that the transverse area of axons is normally maintained constant, which has for a long time been believed to be true without any evidence for it.
Souma
Yuuki
Y
Graduate School of Science and Technology, Shinshu University.
Goto
Noboru
N
Goto
Jun
J
Fujimoto
Tetsuya
T
Fujiwara
Takayuki
T
D000368:Aged; D001369:Axons; D005260:Female; D006801:Humans; D008297:Male; D011712:Pyramidal Tracts / Q000033:anatomy & histology*