All the following openings in the right atrium are guarded by valve EXCEPT

Ans. a (Superior vena cava)# The right atrioventricular (tricuspid) orifice is guarded by tricuspid valve, which maintains unidirectional flow from right atrium to right ventricle.# SVC opens at upper end of right atrium, but has no valve.# IVC opens at the lower end of right atrium and is guarded by a rudimentary valve of Eustachian.# I Coronary sinus opens between opening of IVC and right atrioventricular orifice; it is guarded by valve.CHAMBERS OF THE HEARTRight atrium# Auricle: is derived from the fetal atrium; it has rough myocardium known as pectinate muscles.# Sinus Venarum: is the smooth-walled portion of the atrium, which receives blood from the SVC&IVC.# Crista Terminalis: is the vertical ridge that separates the smooth from the rough portion of the right atrium; it extends longitudinally from the SVC to IVC. SA node is in upper part of the crista terminalis.# Foramen Ovale: In the fetus, the FO is an opening in the interatrial septum, which allows blood entering the right atrium from the inferior vena cava to pass directly to the left side of the heart.Right ventricle# Trabeculae Carneae: ridges of myocardium in the ventricular wall.# Papillary Muscles: project into the cavity of the ventricle and attach to cusps of the AV valve by the strands of the chordae tendinae.0# Chordae Tendinae: control closure of the valve during contraction of the ventricle.# Infundibulum: is the smooth area of the right ventricle leading to the pulmonary valve.Left atrium# Bicuspid Valve: The left AV orifice is guarded by the mitral (bicuspid) valve; it allows oxygenated blood to pass from the left atrium to the left ventricle.Left Ventricle# Blood enters from the left atrium through the mitral valve and is pumped out to the aorta through the aortic valve.# Trabeculae Carneae or ridges of myocardium in the ventricular wall are normally three times thicker than those of the right ventricle.# Papillary Muscles: usually two large ones are attached by the chordae tendinae to the cusps of the bicuspid valve.# Aortic Vestibule: leads to the aortic semilunar valve and ascending aorta; the right and left coronary arteries originate from the right and left aortic sinuses at the root of the ascending aorta.