Where is the $Foramen \text{ } ovale$ (a remnant of embryonic life) located?

$A$: Endocardium provides a smooth lining for the inside of the heart and covers the valves of the heart.
$R$: Endocardium is continuous with the endothelial lining of the large blood vessels associated with the heart and the rest of the cardiovascular system.

Who performed the first heart transplant?

What is the membrane surrounding the heart called?

What is the 'Bundle of $HIS$' a group of?

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