Your Hardworking Heart and Spectacular Circulatory System
A Crabtree Publishing Company www crabtreebooks com 1 800 387 7650
Each living organism is made of tiny building blocks called cells Your heart is made of Specialized cells called cardiac muscle cells CONTENTS YOUR THUMPING HEART HEART PARTS WHAT MAKES A HEART BEAT 10 BLOOD AND IRON WHAT COLOR IS YOUR BLOOD SINUT TYPES OF BLOOD BLOOD VESSELS 16 THE BODY S DELIVERY SERVICE 18 Heart tissue is made of millions of cardiac muscle cells connected together 20 THE BODY S GARBAGE SERVICE DEFENSE AGAINST MICROBE ATTACKS 22 YOUR CIRCULATION OUT OF THIS WORLD 24 26 HELPING HEARTS Your heart is made of cardiac muscle tissue It is the main organ in your circulatory system 28 MAINTENANCE AND SERVICING 30 HEARTY WORDS HEARTY INFORMATION 32 INDEX Your circulatory system runs through your whole and nutrients and Oxygen body de Vivering tak waste
S THUMPING HEART BRILLIANT BODY FACT Press two fingertips onto your inner wrist beneath your thumb Feel that pulse It's caused by your heartbeat Every pulse equals one beat Your heart beats A LOT almost 100 000 times a day over 36 million times a year and 2 5 BILLION times in a person's lifetime A human heart pumps roughly 1 5 million barrels of blood in its and your lifetime Pumping machine smaller size female hearts pump faster at an average of roughly 78 beats per minute for Your heart's job is to pump blood around adults compared to an adult male's 70 beats your body The blood transports the oxygen People who physically fit have slower nutrients the body needs also are a and The blood heartbeat Their hearts are stronger so they carries away waste products This is essential can pump more blood with each beat Some to keep you alive athletes have a heartbeat as low as 30 beats Luckily your heart is REALLY good at pumping per minute or even fewer blood An average adult's heart pumps over 1 981 gallons 7 500 L of blood a day It even generates its own electricity to keep itself going with lers Boys vs girls earts h have th So th Boys hearts are usually bigger than girls The hearts by about 20 because their body size DID YOU KNOW Hearts work 1out their 1eir Human system even whe in electrical ley can car rry on beating Wen separated from the body ey just need a blood supply plus the right conditions to keep their cells alive is generally bigger Partly to make up for their
and from the brain OOK CLOSER WE CIRCULATORY SYSTEMEA THE Laid end to end your blood vessels would circle the world almost 25 times The he Neart pumps blood around Blood and blood vessels the body The blood pumped by the heart travels around the human body through a network of almost 62 000 miles 100 000 km of blood vessels Blood vessels are tubes that run throughout your body to carry blood to and from your heart Veins blue carry blood back to the heart DON T TRY THIS AT HOME In 1929 a German surgeon called Werner Forssmann decided to do an experiment Fred Arteries blood carry away from the heart Forssmann pushed a flexible tube into one of the veins in his arm After about 23 6 inches 60 cm of tube had gone in the end had reached Wermer's heart He had invented a new way of giving patients drugs Werner was later awarded the Nobel Prize for Medicine He lived a long life and died at the age of 74 of heart failure O See for yourself In normal use a healthy heart NEVER gets tired despite beating roughly once every second of your life Try squeezing a tennis ball once a second for a minute or two and you will start to see how amazing this is Werner Forssmann
