Question

there are valves between atria and ventricles

Answer 1

The two atrioventricular (AV) valves, the mitral valve (bicuspid valve), and the tricuspid valve, which are between the upper chambers (atria) and the lower chambers (ventricles). The two semilunar (SL) valves, the aortic valve and the pulmonary valve, which are in the arteries leaving the heart

Answer 2

Atium are the upper part of the heart but ventricle is lower part of the heart

Ateium consist of a thin wall but ventricle consist of a thick wall