Acta Neuropathologica

, Volume 13, Issue 3, pp 197–216 | Cite as

The normal sural nerve in man

I. Ultrastructure and numbers of fibres and cells
  • José Ochoa
  • W. G. P. Mair
Original Investigations


A combined light and electron microscope study of the normal sural nerve in 7 people aged 15–59 years is reported. Qualitative and quantitative studies of the Schwann cells and fibroblasts, myelinated and unmyelinated fibres are made in isolated fascicles.

Schwann cells predominate over fibroblasts in the ratio of about 9-1. Most Schwann cells, almost 80%, are attached to unmyelinated fibres. Factors influencing the densities of these cells per cross sectional area are discussed.

Some ultrastructural features of the myelinated fibres are described and their numbers per and frequency distribution of their sizes are produced. An indirect method is proposed for assessing the mean internodal length for earch of the myelinated fibre size populations in cross sections of fascicles of normal nerves by estimating the proportion of myelinated segments cut through their nucleus.

The ultrastructure of unmyelinated fibres is described and the identification of axons of extreme diameter is discussed. Their densities and size frequency histograms are the first to be reported in man by systematic electron microscope studies. The average ratio of unmyelinated to myelinated fibre density is about 3.7:1 though it varies in the fascicles of the different individuals.

The implications of axonal diameter in the presence of myelin are commented on.


Peripheral Nerves Axons Myelin Sheaths Schwann Cells Electron Microscopy 


Eine kombinierte licht- und elektronenmikroskopische Untersuchung am normalen N. suralis von 7 Menschen im Alter von 15–59 Jahren wurde vorgenommen. Qualitative und quantitative Beobachtungen an Schwann-Zellen und Fibroblasten, markhaltigen und marklosen Fasern wurden an isolierten Faszikeln durchgeführt.

Schwannzellen überwiegen gegenüber Fibroblasten im Verhältnis von etwa 9:1. Die meisten Schwannzellen (etwa 80%) liegen an marklosen Fasern. Die Faktoren, welche die Dichte dieser Zellen pro Querschnittsareal beeinflußen, werden diskutiert.

Einige ultrastrukturelle Befunde an bemarkten Fasern werden beschrieben und ihre Zahl pro mm2 sowie die Häufigkeitsverteilung ihrer Dicke wird angegeben. Eine indirekte Methode zur Bestimmung der mittleren Internodienlänge für jede der Markfasergrößenpopulationen an Querschnitten von Faszikeln normaler Nerven durch Bestimmung des Verhältnisses der markhaltigen Fasersegmente zu ihrer Kernzahl wird vorgeschlagen.

Die Ultrastruktur der marklosen Nervenfaern wird beschrieben und die Identifizierung dieser Axone mit extremen Durchmessern diskutiert. Ihre Dichte und Größenfrequenzhistogramme sind die ersten, die am Menschen durch systematische elektronenoptische Untersuchungen veröffentlicht werden. Das mittlere Verhältnis von marklosen zu bemarkten Fasern ist etwa 3,7:1 und schwankt in den Faszikeln der Einzelindividuen.


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Copyright information

© Springer-Verlag 1969

Authors and Affiliations

  • José Ochoa
    • 1
  • W. G. P. Mair
    • 1
  1. 1.Institute of NeurologyThe National HospitalLondonEngland

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