Can the tricuspid valve and right atrium be seen from the parasternal window?

Yes. In fact, it is standard to angle the transducer toward the right ventricle to obtain the right ventricular inflow view, that is, a view of the right atrium (RA), tricuspid valve (TV), and right ventricle (RV). The interventricular septum (IVS) and inferior vena cava (IVC) are also visible.