The circulatory system in the body is made up of the heart, the blood vessels, and the blood. The circulatory system transports blood throughout the body. It carries oxygen and food to all the cells so that the body can function well and remain healthy. The cells in turn use the oxygen and food to produce heat and energy. Blood serves another purpose apart from transporting oxygen into the cells. It carried wastes such as carbon dioxide from the cells.
The Blood Vessels
Blood is made up of white blood cells, red blood cells, platelets and plasma.
1) Red Blood Cells
The red blood cells are shaped like saucers. They are made in the marrow of long bones and blood derives its color from the red cells. It is estimated that around 50,000 of them could fit on a pinhead. In a single blood cell there is a substance called hemoglobin. Hemoglobin serves as carriers of oxygen which is needed by the cells to function.
2) White Blood Cells
White blood cells are oddly-shaped cells. They are larger than red blood cells. Some of the white blood cells are made in bone marrow through the red cells outnumber the white blood cells. The white blood cells are known as the body’s soldiers. When germs happen to enter body through a cut or other ways, the white blood cells increase in number to fight them. Certain white blood cells kill they germs by surrounding them and ‘eating’ them up. Other white blood cells form a wall around the germs. This process of fighting germs keeps many germs from spreading to the rest of the body. If a person has a sore or boil, the white blood cells would be found in pus around such areas.
Platelets like white blood cells are oddly-shaped. They too serve as protectors. When a person has a cut they control the bleeding. When a blood vessel is cut or damaged “the platelets bind to the site of the damaged vessel, thereby causing a blood clot. There’s an evolutionary reason why they are there. It is to stop us from bleeding,” says Dr. Marlene Williams, Assistant Professor of Medical and CICU and Director of Johns Hopkins Bayview Medical Centre. As the platelets break into smaller pieces around the cut, a special chemical is released. As the blood clots, the opening in the cut blood vessels is blocked. The blood can no longer flow from the cut to the surface of the skin.
Generally, a healthy person should have a platelet count of between 150,000 to 450,000 platelets per micro liter of blood. In the case where a person has more than 450,000,the person is said to have a condition called Thrombocytosis while if a person has les than 150,ooo platelets, the condition is known as Thrombocytopenia.
Red blood cells, white blood cells, and platelets all float in the liquid part of the blood. This liquid is called plasma which is mostly made of water but does contain other substances, for example, food materials and antibodies. (Julius B. and Elonore T.)
Julius B. Richmond and Elenore T. Pounds (1981). You and Your Health. Scott, Foresman and Company, Glenview, Illnois, U.S.A.
Hopkinsmedicine.org, What Are Platelets and Why Are They Important. (Accessed December 18, 2011).