OSTIUM

(Lat.), n. n. Oas'tis-u3m(u4m). A mouth, entrance, aperture, opening. [L, 343.] O. abdominale. The abdominal opening of the oviduct. O. aortae, O. aorticum, O. artenosum aorticum. The opening of the aorta into the heart. [L.] O. arteriosum pulmonale (seu siriistruin). The opening of the pulmonary artery into the heart. [L.] O. atrioventriculare dextrum. The opening between the right auricle and right ventricle of the heart. [L.]O. atrioventriculare sinistrum. The opening between the left auricle and left ventricle of the heart. [L ] O. cutaneum urethrae. The external aperture of the urethra. [L.] O. duodenale. See PYLORUS. O. frontale. The anterior end of the hiatus maxillar is. [A, 319 (a. 48).] O. max ill are. The posterior end of the hiatus maxillar is. [A, 319 (.a, 48).] O. oesophageum ventriculi. The opening of the o ophagus into the stomach. [L, 115.] O. pharyngeum. The pharyngeal opening of the Eustachian tube. [L.] O. pharyngeum laryngis. See GLOTTIS. O. pharyngeum tubas. See O. pharyngeum. O. sinus [Ste i fens and]. The orifice by which the ampulla membranacea opens into the utricle. [L, 7 (a, 50).] O. tubae abdominale. See O. abdominale. O. tubae Eustachii pharyngeum. See O. pharyngeum. O. tubae Eustachii tympani cum. See O tympani cum tubce.O. tubae uterinum. The opening of the oviduct into the uterus. [L.] O. tubuli. The orifice by which the ampulla membranacea opens into the semicircular canals. [L 7 (a, 50).] O. tympani cum tubse. The tympanic orifice of the Eustachian tube. [F, 32.] O. ureter i cum. The opening of the ureter into the bladder. [L, 332.] O. uteri. An old term for the vagina. O. vaginae. Fr., overture vaginale (ou du vag in). Ger., Scheidenoffnung, Schamoffnung. Syn.: vulvo-vaginal ring. The external orifice of the vagina, marking the boundary between that canal and the vulva. Ostea venosa dextra. The openings of the pulmonary veins into the left auricle. [L.] O. venosum sinistrum. See O. atrioventriculare sinistrum. O. ventriculi dextrum (seu duodenale). See PYLORUS. O. ventriculi oesophageum (seu sinistrum). The opening of the oesophagus into the stomach. [L.] [s. 184]