Introduction to Anatomy.

, commonly known as the human threadworm, is a skin-penetrating gastrointestinal parasitic nematode that infects hundreds of millions of people worldwide. Like other species, is capable of cycling through a single free-living generation. Although and the free-living nematode are evolutionarily distant, the free-living adults of are similar enough in size and morphology to adults that techniques for generating transgenics and knockouts in have been successfully adapted for use in . High-quality genomic and transcriptomic data are also available for . Thus, one can use a burgeoning array of functional genomic tools in to probe questions about parasitic nematode development, physiology, and behavior. Knowledge gained from will inform studies of other parasitic nematodes such as hookworms that are not yet amenable to genetic manipulation. This review describes the basic anatomy of .