• At any given time, the veins, and venules typically hold about two-thirds of the blood flowing through the body.
• As the heart contracts and blood rush into the aorta, it is traveling at a speed of about 8 inches (20 centimeters) per second.
• Even in a person who is resting, blood issuing from the heart can travel down to the person's toes and back to the heart in just a minute. when a person is exercising heavily, that trip can take just 10 seconds. On average, every red blood cell completes the heart-to-body-to-lungs circuit 40-50 times an hour.
• If all of the blood vessels in an average adult were strung together end to end, they would reach at least 60,000 miles long, more than twice the distance around the Earth’s equator. The capillaries alone make up 60 percent of that total.
• Every second, 10 million red blood cells die in the normal adult. The body replaces them just as quickly, however, so the total number remains constant.
• In the average adult, the heart weighs less than three-quarters of a pound.
• When a person is resting, the left ventricle pumps about 4–7 liters of blood every minute. In a well-trained athlete who is doing strenuous exercise, that amount can rise to almost 30 liters per minute.
• Heart rate changes greatly during child development. The typical heart rate in a newborn is 130 beats per minute (bpm). It drops to 100 bpm by the time the child reaches 3 years old, 90 at 8 years old, and 85 at 12 years old.
• In increasingly common practice, people are donating blood for use in their upcoming surgeries. Called autologous blood donation, it helps patients ensure safe transfusions (310 grams). In any given person, it’s about the size of his or her fist.
• The heart beats an average of 72 times a minute with a typical at rest volume of 75 ml of blood pumped with each beat. Using those figures, a 75-year-old’s heart has contracted more than 2.8 billion times and pumped more than 212 million liters of blood in his or her lifetime.
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