Articulates are generally suspension feeders, taking in minute particles of nourishment from the water. The lopho-phore is primarily a feeding and respiratory organism. To feed, the lampshell valves open a small gap in the front to allow water to flow over the lophophore. The hollow tentacles, with cilia on the outside, can reach to the front of the valves, while being held near the upper valve. Suspended microorganisms and food particles are trapped in mucus-covered loops and swept by the beating cilia with the intake current down to the mouth through a brachial groove. The mouth leads into an esophagus and stomach, which digests the food. Coelomocyte cells collect nitrogenous material throughout the body and release these wastes into the nephridia, or simple kidneys. The two nephridia have a thin duct leading into the mantle cavity from the coelom so that the wastes can be passed into special outflow currents that carry them away through the animal's mouth. The continual flow of water over the lophophoral arms allows for respiratory exchange of oxygen and carbon dioxide.
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