Tegument

A flatworm’s specialized external covering, which protects the animal and mediates exchange with its surroundings. In parasitic flatworms, it is a living syncytial surface rather than ordinary skin.

Syncytium: A mass of cytoplasm containing multiple nuclei that is not divided into separate cells. The tegument’s outer layer is a syncytium whose nuclei lie beneath the surface.
Cestoda: A class of parasitic flatworms commonly known as tapeworms. Tapeworms absorb much of their nourishment across the tegument because they lack a digestive tract.
Neodermata: A group of parasitic flatworms characterized by a specialized external covering called the neodermis. The tegument is the defining external covering of this major parasitic flatworm group.
Cuticle: A nonliving or extracellular protective layer produced by an organism’s outer cells. Unlike a conventional cuticle, the parasitic flatworm tegument is a living, metabolically active surface.
Microtriches: Microscopic projections on the surface of cestode tapeworms that increase absorptive area. These projections expand the tegument’s contact area with nutrients in the host intestine.
Trematoda: A class of parasitic flatworms that includes flukes. Flukes rely on tegumental surfaces for protection and exchange within host tissues.
Flatworm: An invertebrate in the phylum Platyhelminthes, typically with a flattened body and no body cavity. Tegument is the specialized surface covering found in particular flatworm lineages.
Epidermis: The outer cellular layer of skin in vertebrates and many invertebrates. The tegument performs some epidermal roles but has a distinctive syncytial organization.
Basal lamina: A thin extracellular matrix layer that supports cells and separates them from underlying tissues. It underlies the tegument and separates its surface from internal tissues.
Schistosoma mansoni: A parasitic blood fluke that causes intestinal schistosomiasis in humans. Its tegument is remodeled during maturation and helps the worm persist in blood vessels.

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