Which valve is located between the left atrium and the left ventricle?

$SAN$ generates an action potential which stimulates both the $A$ to undergo a simultaneous contraction called $B$. This increases the flow of the blood into the ventricles by about $C$ percentage. Choose the correct option for $A, B$ and $C$.

The thread-like tendons of papillary muscles inserted upon the flaps of tricuspid and bicuspid valves are:

What is the normal heart rate in a two-month-old infant?

The $Bundle$ $of$ $His$ are:

The blood pumped by the $A$ ventricle enters the $B$ artery,whereas the $C$ ventricle pumps blood into the $D$. Choose the correct option for $A, B, C$ and $D$.