The Heart

This passage details the amazing work of the heart.

Lexile Level: 840L

Categories: Sports & Health Science & Technology Animals & Nature

The heart is an incredible organ. In vertebrates, it is a hollow muscular organ that pumps blood throughout the body. It pumps blood out of itself, and it takes blood into itself. All movement of blood in the body is caused by the heart. It brings oxygen and food to every part of the body. The heart is a specialized muscle. It is the only muscle that contracts and relaxes on its own. It beats at a regular rhythm or pulse. Waves of electrical stimulation pass through it, causing it to beat in this rhythmic pattern. The average human heartbeat, or rhythm, is 72 beats per minute. As a general rule, the larger vertebrates have slower heat rates while smaller vertebrates have faster heart rates. A hummingbird's heart rate averages 1,200 beats per minute. A Grey Whale's heart rate averages 9 beats per minute. No matter what the animal, the heart is an amazing organ.

Hilly Bike Ride

As her bike zoomed down the hill, she anticipated the next climb. After an hour of riding,...



Being overweight and being obese may be defined differently. Someone who is overweight may...


Hay Fever

More than 26 million Americans suffer from hay fever. It has nothing to do with hay, and y...