Answer: Enterobius vermicularis (pinworm) cross-sections
This is a classic histologic appearance of E. vermicularis in cross-section. The diagnosis is made by identification of the lateral alae (singular=ala, from the Latin meaning "wing"). Indeed, you can see why these longitudinal ridges on either side of this roundworm's body have been likened to wings.
Other features include well-developed platymyarian-type musculature (Body musculature consisting of cells not protruding individually into Pseudocoelom), thick muscled esophagus, and thick nucleated intestine; features seen in many intestinal nematodes (round worms).
Some of these features are shown in Case of the Week 88
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