When the ventricles begin to contract, pressure within the ventricles rises and blood flows toward the area of lowest pressure, which is initially in the atria. this backflow causes the cusps of the tricuspid and mitral (bicuspid) valves to close. these valves are tied down to the papillary muscles by these?

The four Science Regents exams (Earth Science, Living Environment, Chemistry, and Physics) also include separately-scheduled lab practicals.
In New York, students have the opportunity to take Regents Exams in grades 9-12 and, when appropriate, in grade eight.