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Related to ostium primum: sinus venosus, foramen primum, Septum primum, Ostium secundum, ostium primum defect
ostium abdomina´le the fimbriated end of the fallopian tube.
ostium cardi´acum the orifice between the esophagus and the stomach.
coronary ostium either of the two openings in the aortic sinuses that mark the origins of the left and right coronary arteries.
ostium inter´num ostium uterinum tubae.
ostium pharyn´geum the nasopharyngeal end of the eustachian tube.
ostium pri´mum an opening in the lower portion of the membrane dividing the embryonic heart into right and left sides. See also atrial septal defect and congenital heart defect.
ostium secun´dum an opening in the upper portion of the membrane dividing the embryonic heart into right and left sides, appearing later than the ostium primum. See also atrial septal defect and congenital heart defect.)
tympanic ostium (ostium tympa´nicum) the opening of the eustachian tube on the carotid wall of the tympanic cavity.
ostium u´teri the external opening of the cervix of the uterus into the vagina.
ostium uteri´num tu´bae the uterine end of the fallopian tube; the point where the cavity of the tube becomes continuous with that of the uterus.
ostium vagi´nae the external orifice of the vagina.
in·ter·a·tri·al fo·ra·men pri·'mum
1. in the embryonic heart, the temporary opening between right and left atria situated between the lower margin of the septum primum and the atrioventricular canal cushions;
2. in an adult heart, the abnormal persistence of the so-named communication, which is normal in young embryos.
The opening in the first septum of the embryonic heart; it closes as the ventricles form.
See also: ostium