The impulse of the heartbeat originates from:

Select the correct option:
$(1)$ The pericardium is a double-layered membrane surrounding the heart.
$(2)$ The $SA$ node has a higher rate of impulse generation compared to the $AV$ node.

During systole of the ventricle:

An artificial pacemaker is implanted subcutaneously and connected to the heart in patients:

Where is the bicuspid valve located in the human heart?

The opening of auricles and ventricles on the right side is guarded by