Functional morphological studies on the correlation between the pedal forms and myofibrous organization

1989 Fiscal Year Final Research Report Summary

• Project/Area Number: 62570017
• Research Category: Grant-in-Aid for General Scientific Research (C)
• Allocation Type: Single-year Grants
• Research Field: General anatomy (including Histology/Embryology)
• Research Institution: Showa University
• Principal Investigator: KIMURA Tadanao Showa University, School of Medicine, Associate Professor, 医学部・第二解剖学教室, 助教授 (70102374)
• Project Period (FY): 1987 – 1989
• Keywords: Skeleton-muscle / Myofibrous organization / Muscle fiber types / Tonic contraction / Phasic contraction / Plastic contraction / Sudan black B / Locomotion

Research Abstract

The pedal forms of mammals are classified into three types: plantigrate type, in which the entire plantar region hits the ground, as seen in Primates and Rodentia ; digitigrade type, in which bones of digits of the foot hit the ground and the metatarsal bone and tarsal bones remain free from the ground, as seen in canines and felines of Carnivora; and unguligrade type, in which bones of the digits of the foot are differentiated into a hoof, as seen in Artiodactyla and Perissodactyla. To analyze locomotion and function of the skeletal muscle according to the pedal forms from the viewpoint of muscle fiber types, specimens of the anterior tibial muscle of the lower extremities from 20 types of mammals in five orders were examined for frequencies of three types of fibers composing the muscle fiber cells, red muscle fiber (Type I, tonic contraction), white muscle fiber (Type II, phasic contraction) and intermediate muscle fiber (Type III, plastic contraction), and these three types of muscle fibers were compared quanrtitatively in terms of the size of the cell.
The frequency of muscle fiber type II (W) was the highest in 16 of the 20 kinds of mammals, accounting for ca. 40 - 49 % of all types. This frequency was followed by Type I (R), ca. 30 - 39% , and Type III (I), ca. 20 - 29%, suggesting a tendency toward predominance of the white muscle type. By contrast, in two kinds of Primates, slow loris and humans, and two kinds of Artiodactyla, giraffes and wild boars, the frequency of R was the highest, showing a tendency toward predominance of Type I . When the size of the muscle fiber cell(mum^2)was determined according to type, in general the R type was the smallest, followed by I and W, in that order. However R was large and W was small in one kind of Primates, slow loris, showing a reversal of the size of the muscle fiber cell in most of the mammals.