P in the heart have thicker muscular walls than Q does. Also, R ensures that blood does not flow back when the atria or ventricles contract. Identify P, Q and R.

P in the heart have thicker muscular walls than Q does. Also, R ensure

1.	P in the heart have thicker muscular walls than Q does. Also, R ensures that blood does not flow back when the atria or ventricles contract. Identify P, Q and R.
Answer» P in the heart have thicker muscular walls than Q does. Also, R ensures that blood does not flow back when the atria or ventricles contract. Identify P, Q and R.