❤️ Heart and Vessels: The Circulatory System

Hello! Today we are visiting the world of the heart and the blood vessels. It works every second and never takes a rest. It is called the circulatory system. Are you ready?

The heart is an organ made of muscle, about as big as your fist. Like a pump, it squeezes and relaxes, and sends blood around the body. That way oxygen and food reach every cell.

The heart is really a double pump. Blood travels along two separate loops: one goes to the lungs and one goes to the body. Blue dots are blood with little oxygen. Red dots are blood with lots of oxygen.

Loop one: the lung loop. Blood goes from the heart to the lungs and back to the heart. In the lungs it drops off carbon dioxide and picks up oxygen. The blue dot turns red.

Loop two: the body loop. Blood with oxygen goes from the heart to the body. It gives oxygen to the cells, takes carbon dioxide, and goes back to the heart as blue blood.

Blood flows in blood vessels. An artery carries blood away from the heart, and its wall is thick. A vein brings blood back to the heart, and it has little valves inside. A capillary is very thin, and things pass through it into the cells. Look at the direction, not the colour.

The liquid part of blood is called plasma. Three kinds of tiny pieces float in it. Red blood cells carry oxygen. White blood cells fight germs. Platelets stop the bleeding when you have a cut.

Every time the heart beats, it pushes blood into the vessels. You can feel that push, gently, in your wrist and your neck. It is called your pulse. The number of pulses is the number of heartbeats.

Let’s try an experiment. At rest, your pulse might be 72 beats in one minute. After thirty jumps it might be 104. Working muscles need more oxygen, so the heart pumps blood faster. When you rest, your pulse slows down again.

Summary: the heart is a double pump. One loop goes to the lungs and one goes to the body. Blood flows through arteries, veins and capillaries. Blood has plasma, red cells, white cells and platelets. Now try it in Cell City!