The Purple Heart is awarded to military members who are injured and killed in combat, through an act of terrorism or by friendly fire. It acknowledges the physical sacrifice of service to the nation.

Your heart first pumps blood to your lungs. Here, the blood picks up oxygen from the air that you have breathed in. The blood (carrying oxygen) then travels back to your heart. The heart gives the ...

Your heart is an exquisitely engineered pump made almost entirely of muscle. And you can see the extraordinary engineering in action if we slow your heart to a single beat. Inside the cavernous ...