Blood, it's type and Rh-factor

Blood

Blood is composed of several kinds of cells (occasionally called corpuscles); these formed elements of the blood constitute about 45% of whole blood. The other 55% is blood plasma, a fluid that is the blood's liquid medium, appearing yellow in color. The normal pH of human arterial blood is approximately 7.40 (normal range is 7.35-7.45), a weak alkaline solution. Blood that has a pH below 7.35 is acidic, while blood pH above 7.45 is alkaline. Blood pH along with arterial carbon dioxide tension (PaCO.) and HCO, readings are helpful in determining the acid-base balance of the body. The respiratory system and urinary system normally control the acid-base balance of blood as part of Mammalian blood homeostasis. Blood is about 7% of the human body weight, (1) so the average adult has volume of about 5 liters, of which 2.7-3 liters is plasma. Human blood density is around 1060 kg/m³ (2) The combined surface area of all the red cells in the human body would be roughly 2,000 times as great as the body's exterior surface.

The cells are:

i. Red blood cells or erythrocytes (96%). In mammals, mature red blood cells lack a nucleus and organelles. They contain the blood's hemoglobin and distribute oxygen. The red blood cell. (together with endothelial vessel cells and some other cells) are also asked by glycoproteins that define the different blood types.

ii. White blood cells or leukocytes (3.0%), are part of the immune system; they destroy infectious agents, pathogens.

iii. Platelets or thrombocytes (1.0%) are responsible for blood clotting (coagulation). 

Blood plasma is essentially an aqueous solution containing 92% water, 8% blood plasma proteins, and trace amounts of other materials. Some components are: albumin, blood clotting factors, immunoglobulins (antibodies), hormones and, various other proteins.

Various electrolytes (mainly sodium and chlorine) together, plasma and cells form a non-Newtonian fluid whose flow properties are uniquely adapted to the architecture of the blood vessels. The term serum refers to plasma from which the clotting proteins have been removed. Most of the protein remaining is albumin and immunoglobulins. 

Blood Facts 

i. The average healthy adult contains between 5 and 6 quarts of blood.

ii. A cubic millimeter of human blood contains about 5 million red blood cells.

iii. Red blood cells are formed in the bone marrow.

iv. Distribution of blood in different organs: Body muscles : about 15%

Bones :about 5%

Body skin : 6%

Brain : about 14%

Kidney : about 22%

Heart : about 27% etc. 

Diseases of blood 

i. Wounds can cause major blood loss. The thrombocytes cause the blood to coagulate, blocking relatively minor wounds, but larger ones must be repaired at speed to prevent exsanguination. Damage to the internal organs can cause severe internal bleeding, or hemorrhage.

ii. Circulation blockage can also create many medical conditions from ischemia in the short term to tissue necrosis and gangrene in the long term.

iii. Hemophilia is a genetic illness that causes dysfunction in one of the blood's clotting mechanisms. This can allow otherwise inconsequential wounds to be life-threatening, but more commonly results in hemarthrosis, or bleeding into joint spaces, which can be crippling.

iv. Leukemia is a group of cancers of the blood- forming tissues.

v. Major blood loss, whether traumatic or not (e.g. during surgery), as well as certain blood diseases like anemia and thalassemia, can require blood transfusion. Several countries have blood banks to fill the demand for transfusable blood. A person receiving a blood transfusion must have a blood type compatible with that of the donor.

vi. Blood is an important vector of infection. HIV, the virus which causes AIDS, is transmitted through contact between blood, semen, or the bodily secretions of an infected person. Hepatitis B and C are transmitted primarily through blood contact. Owing to blood-borne infections, bloodstained objects are treated as a biohazard.

vii. Infection of the blood is bacteremia or sepsis. Malaria and trypanosomiasis are blood-borne parasitic infections.

A, B, O Blood Types

The most well known and medically important blood types are in the A, B and O groups, discovered in 1900 and 1901 at the University of Vienna by Karl Land Steiner in the process of trying to learn why blood transfusions sometimes cause death and at other times save a patient. In 1930, he belatedly received the Nobel Prize for this discovery. All humans and many other primates can be typed for the A, B and O blood groups and blood group AB discovered by Decastello and Sturli in 1902. There are four principal types: A, B, AB, and O. There are two antigens and two antibodies that are mostly responsible for the ABO types. The specific combination of these four components determines an individual's type in most cases. The table below shows the possible permutations of antigens and antibodies with the corresponding blood groups are as follows:

Permutations of antigens and antibodies with the corresponding blood groups:

For example, people with type A blood will have the A antigen on the surface of their red cells (as at in the tables). As a result, anti-A antibodies will not be produced by them because they would cause destruction of their own blood. However, if B type blood is injected into their systems, anti-B antibodies in their plasma will recognize it as alien and burst or agglutinate the introduced red cells in order to cleanse the blood of alien protein.

Individuals with type O blood do not produce ABO antigens. Therefore, their blood normally will not be rejected when it is given to others with different ABO types. As a result, type O people are universal donors for transfusions, but they can receive only type O blood themselves. Those who have type AB blood do not make any ABO antibodies. Their blood does not discriminate against any other ABO type. Consequently, they are universal receivers for transfusions, but their blood will be agglutinated when given to people with every other type because they produce both kinds of antigens. It is easy and inexpensive to determine an individual's ABO type from a few drops of blood. A serum containing anti-A antibodies is mixed with some of the blood. Another serum with anti-B antibodies is mixed with the remaining sample. Whether or not agglutination occurs in either sample indicates the AB0 type. It is a simple process of elimination of the possibilities. For instance, if an individual's blood sample is agglutinated by the anti-A antibody, but not the anti-B antibody, it means that the A antigen is present but not the B antigen. Therefore, the blood type is A.

Blood Compatibility 

Blood is categorized as one of four types: O, A, B, and AB. Another identifier of blood type is the R factor indicated as either positive or negative. The Rh factor is a term for substances found on the surface of the red blood cells, and is named for the rhesus monkey, where it was originally found. Rh factors are generally only an interest in obstetrics.

On the basis blood types and Rh. factor during blood transfusion, the blood type AB is called a universal receiver and blood type O is called universal donor. The capability of blood transfusion is given below:

Blood Transfusion table:

Rh-factor

Rh-Factor of the ABO blood type alleles. There are 2 different alleles for the Rh factor known as Rh+ and p Someone who is "Rh positive" or "Rh+" has at least one Rh+ allele, but could have two Their genotype could be either Rh+/Rh+ or Rh+/Rh-. Someone who Rh- has a genotype of Rh-/Rh- Just like the ABO alleles, each biological parent donates one of their two Rh alleles to their child A mother who is Rh- can only pass an Rh- allele to her son or daughter. A father who is Rh+ could either an Rh+ or Rh-allele to his son or daughter. This couple could have Rh+ children (Rh- from mother and Rh+ from father) or Rh- children (Rh- from mother and Rh- from father).

The Rh factor genetic information is also inherited from our parents, but it is inherited independently pass Rh blood types were discovered in 1940 by Karl Land Steiner and Alexander Wiener. This was 40 years after Land Steiner had discovered the ABO blood groups. Over the last half century, we have learned far more about the processes responsible for Rh types. This blood group may be the most complex genetically of all blood type systems since it involves 45 different antigens on the surface of red cells that are controlled by 2 closely linked genes on chromosome 1. The Rh system was named after rhesus monkeys, since they were initially used in the research to make the antiserum for typing blood samples. If the antiserum agglutinates your red cells, you are Rh+. If it doesn't, you are Rh-. Despite its actual genetic complexity, the inheritance of this trait usually can be predicted by a simple conceptual model in which there are two alleles, D and d. Individuals who are homozygous dominant (DD) or heterozygous (Dd) are Rh+. Those who are homozygous recessive (dd) are Rh-.

Clinically, the Rh factor, like ABO factors, can lead to serious medical complications. The greatest problem with the Rh group is not so much incompatibilities following transfusions (though they occur) as those between a mother and her developing fetus. Mother-fetus incompatibility can when the mother is Rh- (dd) and the father is Rh+ (DD or Dd). Maternal antibodies can cross the placenta and destroy fetal red blood cells. The risk increases with each pregnancy. Europeans most likely to have this problem~13% of their newborn babies are at risk. Actually only about Vi of these babies (6% of all European births have complications. With preventive treatment, this number an be cut down even further. Less than 1% of those treated have trouble. However, Rh blood type incompatibility is still the leading cause of potentially fatal blood related problems of the newborn. In the United States, 1 out of 1000 babies are born with this condition. Rh type mother-fetus incompatibility occurs only when an Rh+ man fathers a child with an Rh- mother. Since an Rh+ father can have either a DD or Dd genotype, there are 2 mating combinations are possible. Only the Rh+ children (Dd) are likely to have medical complications. When both the mother and her fetus are Rh- (dd), the birth will be normal.

The first time an Rh- woman becomes pregnant; there usually are not incompatibility difficulties for her Rh+ fetus. However, the second and subsequent births are likely to have life-threatening problems. The risk increases with each birth. In order to understand why first born are normally safe and later children are not, it is necessary to understand some of the placenta's the mother's antibodies regularly transfer across the placental boundary into the fetus, but her red blood cells usually do not (except in the case of an accidental rupture). Normally, anti-Rh+ antibodies do not exist in the first-time mother unless she has previously come in contact with Rh+ blood. Therefore. her antibodies are not likely to agglutinate the red blood cells of her Rh+ faeutus. Placental ruptures do occur normally at birth so that some fetal blood gets into the mother's system, stimulating the development of antibodies to Rh+ blood antigens. As little as one drop of fetal blood stimulates the production of large amounts of antibodies. When the next pregnancy occurs, a transfer of antibodies from the mother's system once again takes place across the placental boundary into the fetus. The anti-Rh+ antibodies that she now produces react with the fetal blood, causing many of its red cells to burst or agglutinate. As a result, the newborn baby may have a severe life-threatening anemia because of a lack of oxygen in the blood. The baby also usually is jaundiced, fevered, quite swollen and has an enlarged liver and spleen. This condition is called erythroblastosis foetalis.