Morphology of the alimentary tract of Trichinella spiralis muscle larvae with emphasis on the esophagus.

This study was designed to provide a comprehensive description of the ultrastructure of the esophagus of Trichinella spiralis muscle larvae. Although the esophagus exhibited basically the same structure throughout its entire length, being composed of a single cell-layered epithelium, the basal lamina, and the cuticle, some morphological diversity was observed, depending on the level of sectioning. The upper esophagus, devoid of a muscular sheath, was equipped with myofilamentous cytoplasm and a thick cuticle. The middle and lower esophagus was surrounded by the muscular sheath on the basal side and thin cuticle on the luminal side. The cytoplasm usually contained glycogen, ribosomes, and mitochondria. The presence of an amorphous substance in the lumen of the esophagus is reported for the first time. It was completely homogeneous or finely granular and always devoid of any substructure.