Do YoU eVeR wOnDeR wHaT mAkEs Up BlOoD???

Do you ever wonder what makes up blood? Unless you need to have blood drawn, donate it or have to stop its flow after an injury, you probably don't think much about it. But blood is the most commonly tested part of the body, and it is truly the river of life. Every cell in the body gets its nutrients from blood. Understanding blood will help you as your doctor explains the results of your blood tests. In addition, you will learn amazing things about this incredible fluid and the cells in it.

www.biologycorner.com/anatomy/bl...ood.htm
figure 1 : components of blood cells

Blood is a liquid connective tissue that consists of cells surrounded by extracellular matrix. Blood is denser and more viscous than water. The temperature of blood is about 38 ˚C. Its pH is slightly alkaline, ranging from 7.35-7.45. Blood constitutes about 8% of the total body weight. The blood volume is 5 to 6 liters in an average-sizes adult male and 4 to 5 liters in an average-sized adult female. The difference in volume is due to differences in body sizes. Blood is a mixture of two components which are blood plasma and formed elements. Blood plasma is a liquid extracellular matrix that contains dissolved substances. Plasma is about 91.5% water, 7% proteins and 1.5% solutes other than proteins. The plasma protein, are albumins, globulins and fibrinogen which are synthesized mainly by the liver. The solutes dissolved in plasma include electrolytes, nutrients, gases, regulatory substances such as enzymes and hormones, vitamins and waste products. The formed elements of blood contain red blood cells (RBCs), white blood cells (WBCs) and platelets. The RBCs carry oxygen from the lungs, the WBCs help to fight infection and platelets are parts of cells that the body uses for clotting. All blood cells are produced in the bone marrow.

blog.lib.umn.edu/trite001/studyi...2008/02/
figure 2: appearance of centrifuged blood

As children, most of our bones produce blood. As we age this gradually diminishes to just the bones of the spine (vertebrae), breastbone (sternum), ribs, pelvis and small parts of the upper arm and leg. Bone marrow that actively produces blood cells is called red marrow, and bone marrow that no longer produces blood cells is called yellow marrow. The process by which the body produces blood is called hematopoiesis. All blood cells (RBCs, WBCs and platelets) come from the same type of cell, called the pluripotential hematopoietic stem cell. This group of cells has the potential to form any of the different types of blood cells and also to reproduce itself. This cell then forms committed stem cells that will form specific types of blood cells.
The cardiovascular system consists of three interrelated components are blood, heart and blood vessels. Functionally, the cardiovascular system transports substances to and from body cells. To perform its function, blood must circulate throughout the body. The heart serves as the pump for circulation, and blood vessels carry blood from the heart to body cells and from body cells back to the heart. Blood also helps regulate the pH of body fluids. The heat-absorbing and coolant properties of the water in blood plasma and its variable rate of flow through the skin help adjust body temperature. Besides that, blood clots in response to an injury which protects against its excessive loss from cardiovascular system. In addition, white blood cells protect against disease by carrying on phagocytosis and producing protein called antibodies.
The differences in human blood are due to the presence or absence of certain protein molecules called antigens and antibodies. The antigens are located on the surface of the red blood cells and the antibodies are in the blood plasma. There are at least 24 blood groups and more than 100 antigens that can be detected on the surface of red blood cells. The AB0 and Rh systems are the most important ones used for blood transfusions. Not all blood groups are compatible with each other. Mixing incompatible blood groups leads to blood clumping or agglutination, which is dangerous for individuals.
The ABO blood group is based on two antigens called A and B. People who are RBCs display only antigen A has type A blood. Those who have only antigen B are type B. Individuals who have both A and B antigens are type AB and those who have neither antigen A nor B are type O. In addition to antigens on RBCs, blood plasma usually contains antibodies or agglutinins that react with the A or B antigens if the two are mixed. These are the anti-A antibody which react with antigen A and the anti-B antibody which reacts with antigen B. You do not have antibodies that react with your own antigens, but you do have antibodies for any antigens that your RBCs lack.
Many people also have a so called Rh factor on the red blood cell's surface. This is also an antigen and those who have it are called Rh+. Those who haven't are called Rh-. A person with Rh- blood does not have Rh antibodies naturally in the blood plasma. But a person with Rh- blood can develop Rh antibodies in the blood plasma if he or she receives blood from a person with Rh+ blood, whose Rh antigens can trigger the production of Rh antibodies. A person with Rh+ blood can receive blood from a person with Rh- blood without any problems.


learn.genetics.utah.edu/content/begin/traits/blood/
figure 3: blood types
References
•Franklin, 2010. The Franklin Institute[Online]. Available from: [Accessed 12 July 2010].
•Gerard J. Tortora., Bryan Derrickson., 2010. Essentials of Anatomy and Physiology. 8th Ed. The Cardiovascular System: Blood. UK: Bergen Community College, pg358-365.
•Aplatt, 2010. Sickle Cell Information Center [Online]. Available from: [Accessed 12 July 2010].