Cuspid valves are closed
and then open and Semi
Lunar valves are closed
Atria fills with blood
from the Vena Cava and
the Pulmonary vein
Atria contracting
Cuspid Valves are Open
and Semi Lunar valves
are Closed
Forces blood into the
ventricles, the pressure in the
atria is greater than in the
ventricles which are relaxed.
The Semi-Lunar valves are shut
preventing back flow into the
ventricles
Ventricles contracting
Cuspid valves are closed
and the Semi lunar valves
are open