The Circulatory System
The Circulatory System is the system that moves blood throughout the body. This system consists of the heart, blood and blood vessels (arteries, veins and capillaries). The Circulatory System has a very important role; it carries oxygen, nutrients from digested food and other important substances to all parts of the body. It also takes the body’s waste products, including carbon dioxide, away from the tissues. All of this is necessary to keep you alive and healthy.
The Heart
The heart is an amazing organ which is made up mostly of muscle. It continuously pumps blood rich in oxygen, nutrients and other important things to all parts of the body. As the heart beats, it pumps blood through a system of blood vessels. The blood vessels are tubes that carry blood to every part of the body. An adult human heart is about the size of a clenched fist. Look at the diagram of the heart below.
Inside the heart, there are four hollow chambers- a right atrium, a left atrium, a right ventricle and a left ventricle. Blood enters the heart through the atria and leaves through the ventricles. Special valves ensure that blood does not flow in the wrong direction.
The left side of your heart receives blood rich in oxygen from the lungs. This blood is called oygenated blood. In the diagram above, this is shown in red. The left side of the heart then pumps this oxgenated blood around your body. The blood carries oxygen and nutrients to every part of the body. The blood also collects waste materials such as carbon dioxide, that your body needs to get rid of. The blood then travels back to the heart.
The right side of the heart receives blood which is poor in oxygen from all over the body. This is called deoxygenated blood. In the diagram above, this is shown in blue.The right side of the heart pumps this blood to your lungs. In your lungs, blood collects oxygen from the air you breathed in. Also, carbon dioxide from the blood passes into the lungs so you can breathe it out.
Blood Vessels
Blood vessels are tubes that carry blood to all parts of the body. Some are quite large and others are very tiny. There are three main types of blood vessel:
Arteries: Arteries carry blood away from the heart to all of the body’s tissues. They branch several times, becoming smaller and smaller as they carry blood further from the heart and into organs. The largest artery in the body is the aorta (see diagram above).
Veins: These are blood vessels that take blood back to the heart; this blood is poor in oxygen and is rich in waste products, such as carbon dioxide,that will be excreted or removed from the body. Veins become larger and larger as they get closer to the heart. The superior vena cava is the large vein that brings blood from the head and arms to the heart, and the inferior vena brings blood from the abdomen and legs to the heart.
Capillaries: These are small, thin blood vessels that connect the arteries and the veins. Their thin walls allow oxygen, nutrients and other important things to pass from the blood to all parts of your body. At the same time, carbon dioxide and other waste products produced in the body pass into our blood.
What is blood made of?
Blood is made of plasma and blood cells. Plasma is the liquid part of blood. It is made up of water, protein and salt. More than half of your blood is plasma. Blood also contains different types of blood cells. Red blood cells carry oxygen to all parts of the body. White blood cells help the body fight infections. Plateletes help the blood clot when you are bleeding because of a cut or other injury.
Watch the video below to learn more about the circulatory system.