The histological examination of trematodes reveals a simple body plan adapted to a parasitic lifestyle. They possess a tegument, a specialized outer covering that protects them from the host's immune response and aids in nutrient absorption. Beneath the tegument is a layer of muscle fibers that facilitate movement. Internally, trematodes have a primitive digestive system, reproductive organs, and excretory structures. The absence of a circulatory and respiratory system is compensated by diffusion through the body surface.
