Blood

Blood is a body fluid. It transports oxygen and nutrients to the cells. It carries away waste products. Blood has several important roles to play. It helps to maintain our body temperature and normal pH levels in our body tissues. The protective functions of blood include clot formation and the prevention of infection. In many cases it also conveys hormones and disease-fighting substance. Blood is composed of cells suspended in a liquid. In short red cells carry oxygen, white cells fight infection and platelets stop bleeding in injuries.

There are four most important blood components namely: Red cell or Erythrocytes, which are relatively tiny cell without nuclei. The characteristics of these cells are similar to the primitive prokaryotic of bacteria. The red cells normally make up 40- 50 % of the total blood’s volume. They transport oxygen from the lungs to all of the living tissues of the body. They carry away carbon dioxide as waste product. Oxygen is used by cells to produce energy, which the body needs. When the number of red blood cells is too high (Polycythemia), blood also can become too thick, which may cause the blood to clot more easily, which increases the risk of heart attacks and strokes.

White cell or Leukocytes: These white cells or leukocytes exist in variable numbers and types. But they make up a very small part of blood’s volume. They are much, much fewer in numbers than red cells. They dispersed throughout the body but ready at a moment's notice to gather and fight off an invading organism. White blood cells accomplish this by killing or engulfing or digesting those organisms and by producing antibodies that attach to organisms so that they can be more easily destroyed. They are mostly produced in our bone marrow from the same kind of stem cells, which produce red blood cells. Others are produced in the thymus gland- the base of the neck.

Platelets: They are fragments without nuclei that work with blood clothing chemicals at the site of wounds. They do this by adhering to the wall of blood vessels, thereby plugging the rupture in the vascular wall. They also can release coagulating chemicals which cause clots to form in the blood that can plug up narrowed blood vessels. There are more than a dozen types of blood clotting factors and platelets that need to interact in the blood clotting process. Recent research has shown that platelets help fight infections by releasing proteins that kill invading bacteria and some other micro-organisms. Individual platelets are about 1/3 the size of red cells like the red and white blood cells, platelets are produced in bone marrow from stem cells.

Plasma: It is the liquid component of blood, in which the red blood cells, white blood cells, and platelets are suspended. It constitutes more than half of the blood's volume. It consists mostly of water that contains dissolved salts and proteins. The major protein in plasma is albumin. Other proteins in plasma include antibodies (immunoglobulin), which actively defend the body against viruses, bacteria, fungi, and cancer cells and clotting factors, which control bleeding. Normally 55% of our blood’s volume is made up fo plasma. About 95% of it subsists of water.

PROPERTIES

Blood is a serological fluid. It consists of several kinds of cells suspended in a salty aqueous solution called plasma. (If one considers that living organisms such as humans have evolved from species originally living and breathing in salt water, then one might guess that the saline solution of blood plasma is the body’s way of internalizing the seawater and living on dry land). 

The colour of blood comes from the red blood cells (RBC's) or erythrocytes. Red blood cells make up about 40% of volume of blood. This is readily apparent in a simple centrifuge test. Each red blood cell is filled with hemoglobin, the protein which carries oxygen to tissues and carries carbon dioxide (CO2) away from tissues.

Hemoglobin carries oxygen by using heme. Heme is like a large ring-like molecule, which has at its centre of a single atom of iron (Fe). Heme is what actually binds to the oxygen to form an iron (hydr) oxide complex. The chemical property of heme that, gives it these abilities, is in the many double covalent bonds that form the ring.  These double bonds can be shifted into many different “resonant” configurations. This allows for much more oxygen to be carried than if it were simply dissolved in the blood.

There are a variety of cells found within the blood. White blood cells, 'hairy' spherical particles, are instrumental in the body’s immune system by producing antibodies to defend against harmful disease-carrying bacteria, viruses, or fungi. Platelets are white blood cell fragments (also shown above) which assist in blood clotting by aggregating and forming fibres in the opening of a wound which trap red blood cells to form a scab.

Plasma is the liquid portion of blood, and it is about 90% water.  The remaining portion consists of more than 100 different organic and inorganic solutes that are dissolved in water.  Because plasma is a transport medium, it's solutes are continuously changing as substances are added or removed by the cells.

There are a variety of cells found within the blood. White blood cells, 'hairy' spherical particles, are instrumental in the body’s immune system by producing antibodies to defend against harmful disease-carrying bacteria, viruses, or fungi. Platelets are white blood cell fragments (also shown above) which assist in blood clotting by aggregating and forming fibres in the opening of a wound which trap red blood cells to form a scab.

BLOOD GROUPS

The red blood cells have an identical appearance. Protruding from their surface are molecules, called antigens. Antigens vary from person to person and from race to race. The red cells antigens are probably of carbohydrate structure. A person's blood never changes throughout his life. They are classified according to the protein (antigen) present in the red blood cell membrane. There are four types of blood groups namely- A protein, B protein, O (null) and AB protein.

Blood group A: If one belongs to the blood group A, one has  A antigens on the surface of one’s red blood cells and B antibodies in one’s blood plasma.

Blood group B: If one belongs to the blood group B, one has B antigens on the surface of one’s red blood cells and A antibodies in one’s blood plasma.

Blood group AB: If ones belongs to the blood group AB, one has both A and B antigens on the surface of one’s red blood cells and no A or B antibodies at all in one’s blood plasma.

Blood group 0: If one belongs to the blood group 0 (null), one has neither A or B antigens on the surface of one’s red blood cells but he has both A and B antibodies in one’s blood plasma. There are number of other blood groups which do not have much practical importance like MNSS,P,Lu, Le, Wr, etc.

Red cells that have "A" Protein (antigens) are called A Group. Red cells that have "B" Protein (antigens) are called B Group. Red cells that do not have these antigens are called "O" Group. Rhesus Blood Group (Rh) Rh group is named after Macacus Rhesus Monkey, as it resembles the proteins in the red blood cells of Rhesus Monkey. If this Rh protein (antigens) is present in red blood cell of human beings it is called Rh+ve. If this Rh protein (antigen) is absent it is Rh-ve. 95 - 98% of Indians are RH+ve and 2-5% is Rh-ve. Other Blood Groups There are number of other blood groups which do not have much practical importance like MNSS,P,Lu, Le, Wr, etc.

Blood Cells Blood Cells Are Produced In Marrow Red cells, white cells and platelets are made in the marrow of bones, especially the vertebrae, ribs, hips, skull and sternum. These essential blood cells fight infection, carry oxygen and help control bleeding. Plasma Carries Blood Cells Plasma is a pale yellow mixture of water, proteins and salts. One of the functions of plasma is to act as a carrier for blood cells, nutrients, enzymes and hormones.

BLOOD TRANSFUSION

A blood transfusion is a safe, common procedure in which blood is given to you through an intravenous (IV) line in one of your blood vessels.         Blood transfusions are done to replace blood lost during surgery or due to a serious injury. A transfusion also may be done if your body can't make blood properly because of an illness.      During a blood transfusion, a small needle is used to insert an IV line into one of your blood vessels. Through this line, you receive healthy blood. The procedure usually takes 1 to 4 hours, depending on how much blood you need.

 Blood transfusions are very common. Each year, almost 5 million Americans need a blood transfusion. Most blood transfusions go well. Mild complications can occur. Very rarely, serious problems develop.The heart pumps blood through a network of arteries and veins throughout the body. Blood has many vital jobs. It carries oxygen and other nutrients to your body's organs and tissues. Having a healthy supply of blood is important to your overall health. Blood is made up of various parts, including red blood cells, white blood cells, platelets (PLATE-lets), and plasma. Blood is transfused either as whole blood (with all its parts) or, more often, as individual parts.

Blood can be kept in for up to 35 days. Transfusion of whole blood or of blood fractions are used to treat at least 10 different conditions:-whole blood for acute blood loss;  packed red cells far chronic anemia; washed red cells for allergies induced in frequency transfused patients by other elements in the blood. Platelets for bleed caused by platelet deficiency; white cells for low white-cell count in patients with infection; plasma for shock without blood loss; fresh-frozen plasma, freshly drawn plasma or concentrated of the antihemophilic factor of plasma for bleeding in hemophilia; albumin, concentrated from the plasma for shock or for chronic low-album disorder; gamma globulin; fibrinogen, an important clotting factor in the blood.

The undesirable reactions are common occurring for many reasons such as allergy, sensitivity to donor leukocytes, or undetected red-cell incompatibility. Unexplained reactions are also common. There are rare cases of contaminated blood, air bubbles in the blood, overloading of the circulatory system etc. to the donor plasma or platelets.

References:

1.  Bhatia, Dr. N.K., 2005, Clinical, Diagnostic and Therapeutic Services, New Delhi: IGNOU.

2. Safra, Jcaob E., 2010, The New Encyclopaedia Britannica Vol. II, Chicago: Encyclopeadia Britannica, Inc.

3. http://anthro.palomar.edu/blood/blood_components.htm

4. http://www.maexamhelp.com/id97.htm

5.http://www.sigmaaldrich.com/life-science/metabolomics/enzyme-explorer/learning-center/plasma-blood-protein/blood-basics.html