RESUMO
OBJECTIVE: To estimate the number and diameters of myelinated fibres in the tibial nerve[TN]; common peroneal nerve[CPN] and their dorsal and ventral roots L4, L5 and L6 in albino rat. SETTING: Department of Anatomy, Basic Medical Sciences Institute, Jinnah Postgraduate Medical Centre, Karachi. SUBJECT: Male adult albino rats. Period: One year. MATERIAL AND METHODS: The number and diameters of myelinated fibres were estimated from the photomicrographic montages of their araldite embedded transverse sections. The mean count of myelinated fibres in TN was more than CPN while their population in both the dorsal and ventral roots of L5 segment outnumbered the other two segments. The mean diameters of myelinated fibres forming TN and CPN ranged between 2.3-12.2 [micro]m and 2.4-12 [micro]m respectively, while their dorsal and ventral roots measured between 1-12 [micro]m and 2-14 [micro]m. A decrease in the fibre size in both the nerve roots occurred rostrocaudally, however, the size range in the ventral roots appeared to be larger than in the dorsal roots whereas the CPN has slightly more larger sized fibres than the TN