Ostium

(os'-te-um)., a door://., Ostial. In biology, a mouth or mouth-like opening; specifically, one of the slits in the dorsal ve el of certain Crustacea. (Branckippus). O. abdominale, the orifice of the oviduct communicating with the peritoneal cavity. 0. cesophageum ventriculi, the opening of the esophageal or cardiac orifice of the stomach. O., Gastric, the mouth by which a radial canal in sponges opens into the para gaster. O. internum, the orifice at the beginning of the oviduct in the uterus. O. pharyngeum, the pharyngeal opening of the Eustachian tube. O. tympani cum, the tympanic opening of the Eustachian tube. O., Vaginal, the external orifice of the vagina. Dstology (os-tolf-o-je). Same as Osteology. Dstoma (os-to'-mah). Synonym of Osteoma. Dstosis (os-to'-sis). Same as Osteosis. Jstracosis (ps-trak-o' -sis). The degenerative change that sometimes takes place in a portion of bone and causes it to resemble an oyster-shell.