Operculum (fish) required, such as ventilation.. Operculum (fish) The operculum is a series of bones found in bony fish that serves as a facial support structure and a protective covering for the gills; it is also used for respiration and feeding. The opercular series contains four bone segments known as the preoperculum, suboperculum, interoperculum and operculum. The preoperculum is a crescent-shaped structure that has a series of ridges directed posterodorsally to the organisms canal pores. The preoperculum can be located through an exposed condyle that is present immediately under its ventral margin; it also borders the operculum, suboperculum, and interoperculum posteriorly. The
Caudal cell mass The cavities formed from the initial and secondary neuralation combine to form one uninterrupted cavity. There is still specualtion on the formation of the caudall cell mass in humans with arguments being made for it arising from many cavities or the continuing growth of the neurocele from the initial neuralation. The caudal cell mass will ultimately differentiate and form into many sacral structures such various nerve endings and the conus medullaris. The caudal cell mass plays a role in many diseases and abnomalities related to the spinal cord. One group of abnormalities it plays a role in are occult spinal