ostium primum

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 [os´te-um] (L.)
an opening or orifice. adj., adj os´tial.
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.
Miller-Keane Encyclopedia and Dictionary of Medicine, Nursing, and Allied Health, Seventh Edition. © 2003 by Saunders, an imprint of Elsevier, Inc. All rights reserved.

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.
Farlex Partner Medical Dictionary © Farlex 2012

ostium primum

The opening in the first septum of the embryonic heart; it closes as the ventricles form.
See also: ostium
Medical Dictionary, © 2009 Farlex and Partners
References in periodicals archive ?
Accounting for approximately 63% of all DS-CHD, their lesion varies in severity from persistent of the common atrioventricular canal and membranous ventricular septal defects to ostium primum patency with valvular anomalies.
Mitral regurgitation is more frequent in ostium primum type of ASD patients.
Other less common forms of adult ASDs include ostium primum ASD (15% of ASDs), sinus venosus ASD (10% of ASDs), and the unroofed coronary sinus (<1% of ASDs).