The coronary sinus in the heart is situated along its

The valves in the heart allow the blood flow in which direction?
$I.$ From atria to ventricles
$II.$ From ventricles to pulmonary artery
$III.$ From pulmonary artery to aorta
Choose the correct option.

Which of the following minerals is responsible for regulating your heartbeats?

What is the protective covering of the heart called?

Where is the pericardial fluid secreted from?

Choose the correct option: The $AV$ node / $SA$ node is called the pacemaker.