4 INTRODUCING THE HEART If you sit still and put a hand on your chest you can feel something thumping You can even hear it if you listen carefully The organ inside your chest making that noise is your heart The human heart is one of the most The heart is always working to keep the body alive
5 An organ is a part of a person that consists of cells and tissues and performs particular tasks important organs in the body It pumps blood to every other organ which helps move nutrients and wastes through the body The blood moves through a system of tubes called vessels Together the heart and the blood vessels make up the body’s cardiovascular system The heart pumps blood through a vast network of different kinds of blood vessels
6 A heart of an adult weighs about 8 to 12 ounces 230 to 340 grams The heart is a muscle about the size of a person’s fist It is pear shaped and sits high in the chest slightly to the left As humans grow larger the heart grows along with the body The heart is made of very strong muscle This muscle pumps blood by squeezing and relaxing in a regular rhythm This rhythm is called the heartbeat THE HUMAN HEART
7 More than 4 quarts 3 8 liters of blood pass through the heart every minute The heart in a normal body at rest beats anywhere from 60 to 100 times per minute What makes a heart beat faster THINK ABOUT IT Blood is the life fluid of the human body and the liquid that transports nutrients and removes waste Blood travels from the heart to the lungs In the lungs blood releases carbon dioxide and takes in oxygen The blood returns to the heart where it is pumped throughout the body
