Each human being is being kept alive by the combined efforts of body systems, such as the respiratory system, the nervous system, the digestive system, and the circulatory system. The circulatory system contains the heart, and the most essential fluid of all, the blood. Five liters of blood can usually be found circulating inside the body of an adult human being, and blood is responsible for the 7-8% of a person’s weight.

Through the blood, oxygen from the lungs is distributed into different parts of the body, and carbon dioxide produced from metabolism is removed. This same blood disperses the hormones, from glands, that regulate body processes and the nutrients, from digestion, that supply energy and nutrients to the body. And this same blood is the means used by the body’s defense mechanism to fight against diseases. Thus, the blood can be viewed as a river of life. It is made up of plasma and the corpuscles, which are red blood cells, white blood cells, and platelets.

Plasma

More than half of one’s blood (about 55%) is plasma. This blood component can be viewed as the flowing water of the river of life. Through plasma, the blood corpuscles can reach the parts of the body where they are needed. Without plasma, the blood cells and platelets will be frantically struggling to move.

Plasma is composed of about 90% water and the rest are albumin, antibodies, hormones, and other proteins. Plasma carries the salts and minerals that are needed by the body. Some of these are calcium, magnesium, potassium, and sodium.

Red Blood Cells

Red blood cells are red due to the presence of the bright red hemoglobin. Each hemoglobin has iron, which is an element that easily binds itself to oxygen. This is how red blood cells get oxygen from the lungs. As the red blood cells circulate around the body through the arteries, the hemoglobin releases the oxygen and picks up carbon dioxide. Then, red blood cells travel through the veins and back to the heart and lungs in order to remove the carbon dioxide and get more oxygen.

The bone marrow produces the red blood cells. These red blood cells can live in the body for about four months only. With such a short life-span, the bone marrow keeps on producing blood cells to replenish the body’s supply of blood. Since blood is continuously produced, a human being can donate blood.

White Blood Cells

White blood cells are the soldiers of the body. They rush to places in the body where germs have invaded. At the scene of infection, the white blood cells may produce antibodies that kill the germ. If this does not work, the white blood cells themselves surround and eat the germ.

Platelets

Platelets are responsible for the blood clotting phenomenon. With the help of calcium, vitamin K, and fibrinogen, the platelets form a mesh of blood cells that harden upon exposure to air. Such blood clotting saves a human being from hemorrhage or bleeding to death.