Blood

Blood is made of four components

Plasma is a mixture of water, sugar, fat, protein, and potassium and calcium salts. It also contains many chemicals that help form blood the clots necessary to stop bleeding. More than 92% of plasma is water.

Red blood cells contain a special protein called hemoglobin, which carries the oxygen we inhale with our lungs to all of the parts of our bodies. It then returns carbon dioxide from our body to our lungs so we can exhale it. Hemoglobin is also responsible for making red blood cells red. We have so many red blood cells that our blood itself appears red, even though it contains more than red blood cells.

White blood cells are clear round cells that are bigger than red blood cells. White blood cells produce proteins called antibodies that help our bodies fight infections caused by bacteria, viruses, and foreign proteins.

Platelets aren't really cells at all; they are just fragments of cells. When we are injured, platelets gather at the site of the injury and stick to the edges of the wound. They release chemicals that help start the process of blood clotting so that bleeding will stop.

Blood Types

Everybody has a blood type. The most common blood type classification system is the ABO (say "A-B-O") system discovered by Karl Landsteiner in the early 1900s. There are four types of blood in the ABO system: A, B, AB, and O. Your blood type is established before you are born, by specific genes inherited from your parents. You receive one gene from your mother and one from your father; these two combine to establish your blood type. These two genes determine your blood type by causing proteins called agglutinogens (a-GLOO-tin-a-gins) to exist on the surface of all of your red blood cells.

There are three alleles or versions of the blood type gene: A, B, and O. Since everybody has two copies of these genes, there are six possible combinations; AA, BB, OO, AB, AO, and BO. In genetic terms, these combinations are called genotypes, and they describe the genes you got from your parents.

In addition to the proteins (agglutinogens) existing on your red blood cells, other genes make proteins called agglutinins (a-gloo-tin-ins) that circulate in your blood plasma. Agglutinins are responsible for ensuring that only the blood cells of your blood type exist in your body.

Genotype determines blood type

The agglutinogen produced by the O allele has no special enzymatic activities. However, the agglutinogens produced by the A and B alleles do have enzymatic activities, which are different from each other. Therefore people whose genotype is OO are said to have type O blood, meaning the agglutinogen on their red blood cells doesn't have any enzymatic activity. People with Type O blood have agglutinins a and b in their blood plasma. Agglutinin a helps the body destroy any type A blood cells that might enter the circulation system. Agglutinin b helps the body destroy any type B blood cells that might enter the circulation system.

People who have an AA genotype are said to have type A blood because the agglutinogen on their red blood cells has the enzyme activity associated with the A allele. It is important to recognize that people with the AO genotype also have the enzyme activity associated with the A allele, so they are also said to have type A blood. (Remember the O allele doesn't have any enzyme activity associated with it!) People with Type A blood have agglutinin b in their blood plasma. Agglutinin b helps the body destroy any type B blood cells that might enter the circulation system.

Likewise, people with the BB and the BO genotypes are said to have type B blood. These people have agglutinin a in their blood plasma. Agglutinin a helps the body destroy any type A blood cells that might enter the circulation system.

People who have the AB genotype have the enzyme activity associated with both the A and B alleles. These people have no agglutinins in their blood plasma.

The concepts of genotype and phenotype can be easily understood in the case of blood type. Genotype refers the actual genes an individual possesses that determine a particular trait. Phenotype refers to the characteristics of that trait an individual displays. In the case of blood type, both the AA and AO genotypes cause individuals to display the A blood type phenotype. Similarly, both the BB and BO genotypes cause individuals to display the B blood type phenotype. Individuals who are phenotypically type O or type AB have only one possible genotype, OO and AB, respectively.

In different parts of the world, the fraction of individuals with blood type A, B, O, or AB differs. The frequency with which blood types are observed is determined by the frequency with which the three alleles of the ABO gene are found in different parts of the world (allele frequency). Variation in the allele frequency at the ABO gene reflects the social tendency of populations to marry and reproduce within a national, regional, or ethnic group. As people throughout the world intermingle to a greater extent, the distribution of the different blood types will become more uniform throughout the world.

Blood Transfusions

Because there are only four types of blood, it is possible to take blood from one person and donate it to another person in a process called transfusion. In order for a transfusion to work it is essential that the agglutinogens on the surface of the donor's blood cells match the agglutinogens on the surface of the recipient's blood cells. In other words, the blood type of the donor and the blood type of the person receiving the transfusion must be compatible. If the blood types don't match, special antibodies in the recipient's blood, called agglutinins, will attack the donated blood causing blood clots to form in a reaction called agglutination.

If you ever need a blood transfusion, someone will take a sample of your blood in order to determine your blood type and the genotypes of matching blood types. Someone with type A blood can receive blood from people with the AA, AO, and OO genotypes. People with type B blood can receive blood from people with the BB, BO, and OO genotypes.

There are two special genotypes when it comes to blood transfusions

OO and AB

The first special genotype is OO. People with O blood are said to be universal donors because they can donate blood to everybody. However, people with type O blood can only receive transfusions from other type O donors. Because O blood does not carry either the A or B agglutinogens, the immune system of a person with O blood views these agglutinogens as foreign. People with type O blood have agglutinins in their plasma that will react against the A and B agglutinogens.

Therefore, type O blood will undergo agglutination if exposed to A, B, or AB blood. The second special genotype is AB. People with AB blood are said to be universal recipients because they can receive blood from people with all four blood types. Since in AB blood both the A and B agglutinogens are presented on the surface of the red blood cells, the immune system of a person with AB blood views both of these molecules as part of itself - not as something foreign. AB blood does not produce agglutinins against either the A or B agglutinogens, and therefore does not undergo agglutination when exposed to A, B, AB, or O blood.

Blood Donation

If you donate blood , you can help in saving lives of many patients. Thousands of patients need blood transfusion as in the following conditionsPatients suffering from haemorrhage due to casualities, surgical procedures and labours. Haemophilic patients, Chronic Anaemia, Malignancy Thalassemic patients, Bone Marrow transplantation, Neonatal jaundice and others… Blood donation is not hazardous and it proves to be a healthy habit that helps blood renewal. The volume of blood donation is 370:400 ml, almost 7.5% of the adult blood volume.

It is compensated in a short period of time.

When you donate blood, You will get a medical examination including medical history, hemoglobin estimation and blood group determination. The donated blood will be tested for hepatitis B , C , HIV viruses, syphilis microbe, together with liver function tests also HCV RNA by PCR, you will receive the results confidentially or if you want they can be mailed to you.

Adult blood volume is 5 to 6 Liters.Blood is a red coloured fluid that contains continuously renewing cells like red blood cells which renew every 4 months, platelets that renew every week and also white blood cells. The cells are swimming in the liquid part of the blood , the plasma. The blood carries oxygen by RBCs from the lungs into the tissues to generate energy. It carries out carbon dioxide to be expired through the lungs.

White blood cells play a key role in immunity. Plalelets and plasma are responsible for stopping the bleeding from wounds by clotting of the blood.

One can donate blood voluntarily at least twice a year which is safe to his/her health.

Who can donate blood

Those above 17 years.

The body weight should be atleast 50 Kg.

When a women is breast feeding or menstruating, she is allowed to donateonly if she is not fatigued.

Who can’t donate blood

The donor should not be under medication,including antibiotics for ailments, blood pressure, Insulin, asthma medications, aspirin, cholesterol lowering medicines.

Pregnant women

Positive for any of the blood-transferable diseases like hepatitis or HIV/AIDS.

What you need to insist at the blood bank.

Ask for the certification from the state drug controller.

Enquire if all the equipment are working.

Ask for fresh needles and bags to store blood.

Before you donate blood ask for a doctor’s examination.

The doctor should check the weight, blood pressure, anaemia levels.

The blood banks are always having stock of any blood group with proper chilness storage, therefore any one can approach blood banks as per the time of requirements.

Of course blood banks are the safe place to get blood.

After receiving blood from blood bank, one should properly transport it by all means carefully.

While donating blood means you are giving/saving life.