© Illustration: Science Photo Library
Heart and circulatory system diseases can be life-threatening. But heart medicine has made great strides in recent decades.
The heart beats an inch under the skin, slightly offset to the left behind the breastbone between the second through fifth ribs. It's a perfectly engineered muscle, a powerful, nearly maintenance-free pump built to last. The heart begins to work early, life has barely emerged: just four weeks after an egg cell meets a sperm cell, the heart has developed from a simple vascular tube into a complex organ that
