what is the circulatory system?

What are the components of the circulatory system?

What are veins?

what are arteries?

What are blood vessels?

What is blood?

How is the heart divided into?

What is the main function of the heart?

How can we take care of the heart?

What are the conditions that may affect you heart?

How many valves are there inside the heart?

What are the names of those valves?