The heart is the body's hardest-working muscle. Whether you're awake or asleep, or exercising or resting, your heart is always at work. It pumps blood through arteries to deliver oxygen to organs ...

Scientists are starting to understand more about the small heart muscle fibers that Da Vinci showed in his illustrations over 500 years ago.

model, anatomical, human heart Measurements overall: 6 3/8 in x 4 1/8 in; 16.1925 cm x 10.4775 cm overall: 16.2 cm x 11.3 cm; 6 3/8 in x 4 7/16 in place made Germany: Saxony, Leipzig Associated Place ...