Tapeworms pinyin tāochóng, are huge intestinal parasites, with the average adult reaching 72 feet (21.9456 m) in length.

Adults parasitize vertebrates, and larvae primarily parasitize invertebrates or use vertebrates as intermediate hosts.

Tapeworms have a well-developed muscular system. The cortex of the body surface is densely covered with microhairs, under which there is a thin circular muscle, two layers of longitudinal muscle under the circular muscle, and a subcutaneous matrix between the outer and inner layers. Below the longitudinal muscle is the transverse muscle. Between the transverse muscle and the cortex is called the cortical zone, and between the two layers of transverse muscle is called the medullary zone. Important stylized in the reproductive organs are located within the medullary zone.

The nervous system has ganglia in the cephalic ganglion connected to the transverse nerves, which form the central nervous system, from which emanates backward 1 pair of longitudinal nerve trunks up to the last somites of the worm.

The excretory system has ring excretory ducts in the cephalic ganglion, from which 2 pairs of dorsal and ventral excretory ducts emanate on either side to the end of the body. The posterior margin of each somite has a transverse tube connected to the ventral excretory ducts. In addition, there are many flame cells in the body tissue, each with a small tube leading to the ventral excretory duct. The excretory system has the function of balancing and regulating water.

Human parasitic tapeworms belong to Pseudophyllotrichida and Cyclophyllotrichida. Pseudophyllotrichida tapeworms have pike-shaped head segments, and the fixation organ is the suction groove located on the dorsal and ventral surfaces of the head segments; the yolk glands are follicularly dispersed in the surface layer of the segments, and the ovaries are before the yolk glands; the genital pore is located in the middle of the segment; the uterus has a uterine pore that leads to the outside of the body; and the adult segments and the pregnant segments are similar in structure.

The head segment of the Cyclophyllidea is spherical, the fixation organs are four suckers, as well as the parietal and small hooks, etc.; the yolk glands are aggregated into a single piece, which is situated after the ovary, and the genital pore is situated on the lateral side of the segment; there is no uterine aperture, and there is a large difference in the structure of the gestational segment and the adult segment.