The heart is an organ about the size of your fist. It pumps blood through your body. It sits in your chest between your lungs, a little to the left of the middle. Your heart is made of muscle. The heart has four chambers. A wall of tissue called the septum divides the right and left sides of the heart. Put a hand on your chest to find it. Then let us look at how it works.
Each heartbeat starts with an electrical signal. The signal comes from the sinoatrial (SA) node in the right atrium. The SA node is the heart's pacemaker, and it sets the rate of the heartbeat. The signal first makes the atria contract and push blood into the ventricles. The ventricles are the two lower chambers of the heart, and they pump blood out of the heart. Between beats, the heart relaxes and its ventricles fill with blood.
Now let us look at the valves. Valves inside the heart keep blood moving in the right direction, and the heart has four valves. A heartbeat makes a "lub-DUB" sound. The "lub" is made by the valves between the atria and ventricles closing. With each heartbeat, the heart sends blood throughout your body. The blood carries oxygen to every cell, and the left ventricle pumps oxygen-rich blood to the whole body.
After the blood delivers oxygen, it returns to the heart, and the heart sends it to the lungs to pick up more oxygen. Your body contains about 60,000 miles of blood vessels. You can feel your pulse on the inside of your wrist. Your pulse is the rate your heart beats, also called your heart rate. To find your heart rate, count the beats you feel in 30 seconds and double the number.
Last, let us think about how to look after it. At rest, a heart rate of 60 to 100 beats per minute is normal for adults. Your heart pumps more or less blood depending on what your body needs. When you exercise, your heart beats faster to get more oxygen to your muscles. Running, biking and swimming are exercises that are good for your heart, so they are good ways to look after it.
Words to know
- pacemaker: beat starter
- septum: dividing wall
- ventricles: lower chambers
- sinoatrial: beat-starting spot
- valves: one-way gates
