Internal Morphology

Abstract

The cells of the somatic musculature of nematodes are, with few exceptions, longitudinally oriented and spindle-shaped. Each cell is composed of two regions: a noncontractile portion that gives rise to the myoneural process and a contractile portion. The noncontractile region can be further described as the body of the cell containing the sarcoplasm and nucleus. From the body of the cell a process extends to the neural junction, a condition unique to nematodes (Fig. 4.1A). The contractile portion consists of oblique contractile elements variously arranged within the muscle fibers. The muscle bands are composed of two or more fibers (cells) that are grouped into four sectors in any given body cross section: two subdorsal and two subventral. These muscle band quadrants are separated from each other by the four major hypodermal chords (Fig. 2.8).