The opening of the pulmonary vein is without a valve because

The 'dubb' heart sound is produced at the time of closure of:

Draw a labelled diagram showing the internal structure of the human heart.

The '$Bundle$ of $His$' is a group of which of the following?

Analogy type questions:
$(1)$ Right atrium and right corner : $SA$ node :: Corner of right atrium : .......
$(2)$ First heart sound : $Lubb$ :: Second heart sound : ...........

The heartbeat of a human is heard on the left side because: