In humans, the circulatory system has three distinct components.
Blood (A fluid that can circulate in the body)
Heart (A pump that can circulate the blood around the body)
Blood vessels (Tubes that help the blood to circulate.)
Blood vessels:
The heart circulates blood across the body through a network of tubes called blood vessels. There are three kinds of blood vessels; arteries, veins and capillaries.
Arteries carry blood away from the heart.
Veins carry blood back to the heart.
Capillaries exchange oxygen, food, carbon dioxide and waste products between the blood and the body cells. They do this through their very thin wall.
The Heart:
The heart is a double pump which pumps the blood through arteries and veins. A thick, muscular wall, called the septum, divides the heart into two halves; which are further divided into the atrium and the ventricles. When the heart muscles relax, the blood enters the atrium. When the atrium contract, the blood enters the ventricles. When the ventricles contract blood is forced into the rest of the body by the left ventricle and to the lungs by the right ventricle. The blood from the lungs come back to the left atrium and from the rest of the body to the right atrium.
Blood:
In humans, blood is the medium of transport which is pumped by an organ called the heart. Blood is a liquid consisting of plasma, red blood cells, platelets and white blood cells. Blood helps in the transportation of various substances, protection of the body against diseases as well as regulation of temperature and water content in the body. Every person has an individual blood group. These groups are named A, B, AB and O. A and B refer to the certain substances present in the red blood cells. Blood groups are inherited and do not change throughout the life.
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