open access

Vol 78, No 2 (2019)
Original article
Submitted: 2018-08-22
Accepted: 2018-10-03
Published online: 2018-10-19
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Morphological study of myelinated and unmyelinated fibres in the sacrococcygeal dorsal roots of the rat

J.-C. Lee1, C.-H. Cheng2, C.-T. Yen1
·
Pubmed: 30371932
·
Folia Morphol 2019;78(2):267-273.
Affiliations
  1. Department of Life Science, National Taiwan University, Taipei, Taiwan
  2. Department of Veterinary Medicine, National Taiwan University, Taipei, Taiwan

open access

Vol 78, No 2 (2019)
ORIGINAL ARTICLES
Submitted: 2018-08-22
Accepted: 2018-10-03
Published online: 2018-10-19

Abstract

Background: The number and calibre of myelinated and unmyelinated fibres of the sacrococcygeal dorsal roots innervating the tail of rats were studied by means of light and electron microscopy.

Materials and methods: There were an estimated total of 12,500 myelinated and 25,500 unmyelinated dorsal root fibres innervating the tail of a rat. 

Results: The results showed that from the second sacral (S2) to the fourth sacral (S4) segment, the fibre diameter spectrum of myelinated fibres within each dorsal root was bimodal with two peaks at 5 microns and 10 microns, respectively. The first sacral (S1) segment was composed of numerous smaller-size myelinated fibres, thus forming a right-skewed distribution. The coccygeal (Co) segments showed a unimodal distribution peaking at 10 microns for the first (Co1) segment and gradually shifting to 7 microns for the third (Co3) segment. Overall, there was a continuous relative increase of the larger vs. the smaller myelinated fibres from the sacral to coccygeal segments. The fibre diameter of unmyelinated fibres of all these roots was unimodal with a single peak at 0.5 microns. The ratio of unmy- elinated to myelinated fibre numbers was on average 2.83 for the S1–S2 roots, 1.66 for the S3–S4 roots, and 1.24 for the coccygeal roots. 

Conclusions: The comparison of the left- and right-side nerve fibres show that there was no significant difference, thus implying a symmetrical sensory innervation of the rat’s tail. 

Abstract

Background: The number and calibre of myelinated and unmyelinated fibres of the sacrococcygeal dorsal roots innervating the tail of rats were studied by means of light and electron microscopy.

Materials and methods: There were an estimated total of 12,500 myelinated and 25,500 unmyelinated dorsal root fibres innervating the tail of a rat. 

Results: The results showed that from the second sacral (S2) to the fourth sacral (S4) segment, the fibre diameter spectrum of myelinated fibres within each dorsal root was bimodal with two peaks at 5 microns and 10 microns, respectively. The first sacral (S1) segment was composed of numerous smaller-size myelinated fibres, thus forming a right-skewed distribution. The coccygeal (Co) segments showed a unimodal distribution peaking at 10 microns for the first (Co1) segment and gradually shifting to 7 microns for the third (Co3) segment. Overall, there was a continuous relative increase of the larger vs. the smaller myelinated fibres from the sacral to coccygeal segments. The fibre diameter of unmyelinated fibres of all these roots was unimodal with a single peak at 0.5 microns. The ratio of unmy- elinated to myelinated fibre numbers was on average 2.83 for the S1–S2 roots, 1.66 for the S3–S4 roots, and 1.24 for the coccygeal roots. 

Conclusions: The comparison of the left- and right-side nerve fibres show that there was no significant difference, thus implying a symmetrical sensory innervation of the rat’s tail. 

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Keywords

tail; dorsal root; axon diameter; frequency distribution

About this article
Title

Morphological study of myelinated and unmyelinated fibres in the sacrococcygeal dorsal roots of the rat

Journal

Folia Morphologica

Issue

Vol 78, No 2 (2019)

Article type

Original article

Pages

267-273

Published online

2018-10-19

Page views

1938

Article views/downloads

1185

DOI

10.5603/FM.a2018.0100

Pubmed

30371932

Bibliographic record

Folia Morphol 2019;78(2):267-273.

Keywords

tail
dorsal root
axon diameter
frequency distribution

Authors

J.-C. Lee
C.-H. Cheng
C.-T. Yen

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