Humans cannot live without blood. Without blood, the body’s organs wouldn’t get the oxygen and nutrients they need to survive. The body itself wouldn’t be able to keep warm, cool off, fight infections or get rid of waste products. Blood is crucial for life.
Life to the Body
By Judith Nembhard
The Function of Blood
The adult human body contains approximately five liters of blood that makes up between seven and eight percent of a person’s body weight. The heart pumps blood to provide oxygen and nutrients to every cell in the body, but it would be impossible for the heart to survive without blood flowing through the vessels, bringing nourishment to its walls. This means a healthy relationship between blood and the heart is essential for overall good health, since the body depends on having a constant supply of energy and oxygen to its trillions of cells.
Blood contains important substances from the food our digestive system processes as well as hormones released by the endocrine glands. It transports carbon dioxide and other waste materials to our lungs, kidneys and digestive system in order to remove these substances from the body. Blood works hard to keep our bodies healthy.
Blood Vessels
Blood flows through a vast network of arteries and veins. It flows away from the heart to the rest of the body through arteries that carry oxygenated blood, or blood that has received oxygen from the lungs. The process is then reversed as the blood travels through the veins back to the heart and lungs to receive a new supply of oxygen. It is possible to feel the blood coursing through the body at pulse points such as the neck and wrist. These are places where large, blood-filled arteries are close to the surface of the skin.
The blood flowing through this network of veins and arteries is made up of plasma and three kinds of blood cells: red blood cells, white blood cells and platelets.
Plasma, the yellowish liquid part of the blood, is about 90 percent water and makes up approximately 55 percent of the total blood volume.
According to Mark Womack, M.D., a hematologist at Chattanooga Oncology and Hematology Associates, plasma is essential for human survival. Red blood cells, white blood cells and platelets travel by way of plasma. Without it, the lifegiving blood cells would be left without a means of getting around in the body.
Red Blood Cells (RBCs)
Our bodies contain more red blood cells than any other kind. Each red blood cell has a lifespan of about four months. New RBCs are produced every day to replace those that die or are lost from the body.
Red blood cells, also called erythrocytes, are slightly indented, flattened disks containing the iron-rich protein hemoglobin. The blood gets its rich red color when hemoglobin picks up oxygen in the lungs. As the blood travels through the body, hemoglobin releases oxygen to the tissues.
Diseases of the Red Blood Cells
Although blood usually functions without any problems, sometimes blood disorders or diseases occur. Anemia is the most common condition affecting red blood cells, says Dr. Womack. He also states that anemia occurs when there is a lower than normal number of red cells in the blood. He cites fatigue as a symptom of the disease, but says a person may experience fatigue but not suspect that he or she has anemia. Other symptoms he cites are a decrease in exercise tolerance, shortness of breath and pale skin. Dr. Womack also said that in rare cases, anemia can result from insufficient folic acid and vitamin B-12 in the diet. Essentially, the blood’s reduced capacity to carry oxygen causes anemia. In severe cases of chronic anemia, an individual may need a blood transfusion.
Reduced red blood cell production may also result in iron deficiency anemia, which is the most common type. It most commonly affects kids, teenagers who have a diet low in iron, and pregnant women.
Lead poisoning is another condition affecting the red blood cells. When lead enters the body, most of it goes directly to the red blood cells and interferes with the production of hemoglobin. Lead poisoning is less common today, but it still poses a problem.
Sickle cell anemia is well known and is most prevalent among people of African descent. A hereditary disease, sickle cell anemia results in the production of abnormal hemoglobin. In this type of anemia, the red blood cells cannot carry oxygen adequately and are easily destroyed. Increased red blood cell destruction occurs in both children and adults with sickle cell anemia.
White Blood Cells (WBCs)
White blood cells are the body’s fighter cells and are the key factors in helping the body fight infection. They can move in and out of the blood stream to reach affected tissues and are continually on the lookout for signs of disease. When someone has an infection, the white blood cell count is often higher than usual because more WBCs are entering the blood stream to fight the infection.
As soon as a germ appears, the white blood cells attack in a variety of ways. Many fight bacteria and viruses by attempting to destroy cells that have become infected or cells that have changed into cancer cells. They do this by surrounding and devouring the intruder. Other kinds of WBCs produce special proteins called antibodies that identify foreign materials in the body and help destroy or neutralize them.
The lymphocyte, a specific kind of white blood cell, makes up 25 to 33 percent of the total number of white blood cells. Although they are in the general circulation, lymphocytes are concentrated in areas such as the spleen, the tonsils and the lymph nodes, where the internal immune response is likely to take place.
Lymphocytes are responsible for immune reactions to microorganisms and other foreign substances that enter the body. They are said to be able to “remember” how to make the specific antibodies that will attack the same germ if it enters the body again. There are two main types of lymphocytes: B cells and T cells. B cells make antibodies that attach to bacteria that has invaded the body. T cells attack and kill the infected cells. Lymphocytes often alter the activities of other types of cells and can be found at the site of chronic inflammation.
Platelets, also called thrombocytes, are tiny oval-shaped cells made in the bone marrow that are essential for making blood clot. When a blood vessel breaks, platelets go to the affected area, seal off the leak, and temporarily stop the bleeding or slow it down. Platelets work in conjunction with important proteins called clotting factors to seal off wounds, cuts and scratches. They prevent bleeding on the inside of our bodies as well as on the outside. Platelets are constantly being replaced by new cells and have a survival rate of only about nine days.
By themselves, platelets can plug small leaks in blood vessels and slow the bleeding, but the clotting factors are needed to create a stronger seal. However, if a large blood vessel is cut, the blood may not be able to do the repair job by clotting. In such a case, stitching or bandaging is used to help control the bleeding.
Blood Types
All blood is made up of the same basic elements, but not all blood is alike. Blood type is inherited, or passed on genetically from parent to child. Different blood types are based on the presence or absence of what are called antigens—substances that elicit an immune response if they are foreign to the body.
There are 4 major blood groups: A, B, AB and O. These are determined by the presence or absence of the two antigens A and B on the surface of red blood cells. Blood Group A only has the A antigen on the red blood cells, and Group B only has the B antigen. Group AB has both A and B antigens. People with blood group O have neither A nor B antigens. Type O donors can give to any blood type, but they can only receive blood from other O donors. O negative blood does not have any antigens and is known as the universal donor.
A third antigen exists in addition to the A and B antigens. It is called the Rh factor, and it refers to whether or not individuals have an additional antigen on the surface of their red blood cells. If the antigen is on the surface of a person’s red blood cells, he or she has Rh positive blood. If the antigen is not there, he or she has Rh negative blood. Generally, Rh negative blood is given to Rh negative patients. Either Rh positive or Rh negative blood may be given to Rh positive patients. A person’s specific blood type is determined by his or her blood group and Rh factor.
Donating Blood
Blood is “always in demand,” Dr. Womack asserts. Millions of patients benefit from donated blood annually. It is said that one pint of blood can save as many as three lives.
A blood transfusion can replace blood that is lost, and whole blood can be transfused, but it is rarely used in that state. Instead, specific parts of the blood are transfused to the patient as needed. Red blood cells are the most commonly used part; they increase the blood’s ability to transport oxygen and prevent fatigue and other complications in the patient.
Since there is no good man-made substitute for human blood, the blood used in emergencies must be donated. Some blood donations come from people who know in advance they will need a transfusion for a planned surgery, so they donate their own blood beforehand. Sometimes a family member or friend with a compatible blood type donates blood specifically for the use of a particular patient.
Most donated blood, however, comes from volunteers who contribute to blood drives run by organizations such as Blood Assurance. There is no evidence that your blood or a family member’s blood is any safer than blood donated by volunteers. Some people worry about contracting a disease from unsafe or infected blood, but Dr. Womack states that “there are many safeguards in place to ensure the safety of [donated] blood.” The blood is screened for the HIV virus and hepatitis, he says, and the likelihood of a person being infected from a blood transfusion is one in several millions. The United States is said to have one of the safest blood supplies in the world.
Here in Chattanooga, Blood Assurance, a non-profit regional blood center, is commited to providing a safe and adequate supply of blood to area patients. Blood drives held by the group and daily donations help ensure a life-giving source will be on the shelf whenever needed.
The body is wonderfully made, and an impressive part of the body is the river of life that flows through it, replenishing itself as it performs its functions.
Judith P. Nembhard is a Chattanooga resident. She is a graduate of the University of Maryland where she received her Ph.D. in English education. Judith is a member of the Chattanooga Writers Guild and has two sons. Judith is a lifelong educator and a published writer.

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