The principal oral and sensory organs are located in the head, including the mouth, pharynx, photo and chemo receptors. The head bears four tufts of sensory cilia, sometimes mounted on lobular projections. The brain of gastrotrichs is derived from the combination of two cerebral ganglia, extending one longitudinal nerve cord. Simple ocelli provide the animal with basic visual information. The pharynx is connected to the gastro-intestinal tract and to the lateral pharyngeal pores.
Pharyngeal pores allow for expulsion of water that is taken in whilst feeding.
The epidermis is syncitial and covered dorsally by scales, bristles and ventral cilia. Bristles and cilia may be spread evenly over the surface, or grouped in bands and stripes of cirri. These tufts of bristles clearly serve a tactile sensory function. Adhesive tubules also project from the epidermal surface and provide a means of short-term attachment for the organism. The arrangement of these epidermal projections varies considerably amongst different taxa, and can be used as distinguishing features in their identification.