Ключевые слова: annelid, annelida, biology class, blood vessels, body cavity, circular fibers, circular muscle, coelom, compound microscope, cross section, cuticle layer, digestive tract, dorsal blood, epidermal cells, epidermis, flattened body, flattened shape, gut cavity, hematophagous, high magnification, histological section, internal organs, internal segmentation, intestine, leech, leech anatomy, longitudinal muscle, microscopy image, mucus gland, muscle fibers, muscular wall, nephridium, nervous system, parasitic worm, pharynx tube, prepared slide, reproductive organ, scientific study, segmental structure, segmented body, setae absent, stained slide, stained tissue, sucker attachment, tissue layers, transverse cut, vascular system, ventral nerve, zoological specimen,