- Blood type
A blood type (also known as a blood group) is a classification of
blood, based on the presence and absence of antibodies and
inherited antigenic substances on the surface of red blood cells
(RBCs). These antigens may be proteins, carbohydrates,
glycoproteins, or glycolipids, depending on the blood group system.
Some of these antigens are also present on the surface of other types
of cells of various tissues.
There are two types of Blood grouping system:
ABO blood group system
Rh blood group system
- ABO blood group system
The ABO blood group system involves two antigens and two
antibodies found in human blood. The two antigens are antigen A and
antigen B. The two antibodies are antibody A and antibody B. The
antigens are present on the red blood cells and the antibodies in the
serum. Regarding the antigen property of the blood all human beings
can be classified into four groups, those with antigen A (group A),
those with antigen B (group B), those with both antigen A and B
(group AB) and those with neither antigen (group O).
The antibodies present together with the antigens are found as
follows:
Antigen A with antibody B
Antigen B with antibody A
Antigen AB with neither antibody A nor B
Antigen null (group O) with both antibody A and B
- Phenotype and genotype of blood types
I -Dominant trait
i -Recessive trait
- Rh blood group system
The Rh system (Rh meaning Rhesus) is the second most significant
blood-group system in human-blood transfusion with currently 50
antigens. The most significant Rh antigen is the D antigen, because
it is the most likely to provoke an immune system response of the
five main Rh antigens. It is common for D-negative individuals not to
have any anti-D IgG or IgM antibodies, because anti-D antibodies
are not usually produced by sensitization against environmental
substances. However, D-negative individuals can produce IgG anti-
D antibodies following a sensitizing event: possibly a fetomaternal
transfusion of blood from a fetus in pregnancy or occasionally a
blood transfusion with D positive RBCs. Rh disease can develop in
these cases. Rh negative blood types are much less common in
Asian populations (0.3%) than they are in European populations
(15%).
The presence or absence of the Rh(D) antigen is signified by the +
or − sign, so that, for example, the A− group is ABO type A and does
not have the Rh (D) antigen.
- Blood transfusion
There is an agglutination reaction between similar antigen and
antibody (for example, antigen A agglutinates the antibody A and
antigen B agglutinates the antibody B). Thus, transfusion can be
considered safe as long as the serum of the recipient does not
contain antibodies for the blood cell antigens of the donor.
The ABO system is the most important blood-group system in
human-blood transfusion. The associated anti-A and anti-B
antibodies are usually immunoglobulin M, abbreviated IgM,
antibodies. It has been hypothesized that ABO IgM antibodies are
produced in the first years of life by sensitization to environmental
substances such as food, bacteria, and viruses, although blood
group compatibility rules are applied to newborn and infants as a
matter of practice. The original terminology used by Karl
Landsteiner in 1901 for the classification was A/B/C; in later
publications "C" became "O". Type O is often called 0 (zero, or null)
in other languages.
- Erythroblastosis Fetalis
The adult human body is home to trillions of red blood cells, also
known as RBCs or erythrocytes. These blood cells carry oxygen, iron,
and many other nutrients to the appropriate places in the body.
A special case of Rh incompatibility (mismatching)has been observed
between the Rh-ve blood of a pregnant mother withRh+ve blood of
the foetus. Rh antigens of the foetus do not get exposed to the Rh-ve
blood of the mother in the first pregnancy as the two bloods are well
separated by the placenta. However, during the delivery of the first
child, there is a possibility of exposure of the maternal blood to small
amounts of the Rh+ve blood from the foetus. In such cases, the
mother starts preparing antibodies against Rh antigen in her blood. In
case of her subsequent pregnancies, the Rh antibodies from the
mother (Rh-ve) can leak into the blood of the foetus (Rh+ve) and
destroy the foetal RBCs.This could be fatal to the foetus or could
cause severe anaemia and jaundice to the baby
This condition is highly preventable and the typical, severe form is
now very rare in developed countries. Catching it early can ensure a
successful pregnancy for mother and child. If left untreated, however,
it can be life threatening for the baby.
Erythroblastosis fetalis is now known as hemolytic disease of the
newborn.
- How is erythroblastosis fetalis diagnosed?
To diagnose erythroblastosis fetalis, a doctor will order a routine
blood test during the first prenatal visit. They’ll test for the blood
type.
The test will also help them determine whether they have anti-Rh
antibodies in their blood from a previous pregnancy.
The fetus’s blood type is rarely tested. It’s difficult to test for a
fetus’s blood type and doing so can increase the risk for
complications.
- Lymph:-
Lymph is the fluid that flows through the lymphatic system, a system
composed of lymph vessels (channels) and intervening lymph nodes
whose function, like the venous system, is to return fluid from the
tissues to be recirculated. At the origin of the fluid-return process,
interstitial fluid—the fluid between the cells in all body tissues[2]—
enters the lymph capillaries. This lymphatic fluid is then transported
via progressively larger lymphatic vessels through lymph nodes,
where substances are removed by tissue lymphocytes and circulating
lymphocytes are added to the fluid, before emptying ultimately into
the right or the left subclavian vein, where it mixes with central
venous blood. Because it is derived from
interstitial fluid, with which blood and
surrounding cells continually exchange
substances, lymph undergoes continual
change in composition. It is generally
similar to blood plasma, which is the
fluid component of blood. Lymph returns
proteins and excess interstitial fluid to
the bloodstream. Lymph also transports
fats from the digestive system.
- Coagulation of blood:-
Blood exhibits coagulation or clotting in response to an injury or
trauma. This is a mechanism to prevent excessive loss of blood from
the body coagulam formed mainly of a network of threads called
fibrins in which dead and damaged formed elements of blood are
trapped. Fibrins are formed by the conversion of inactive fibrinogens
in the plasma by the enzyme thrombin. Thrombins, in turn are
formed from another inactive substance present in the plasma
called prothrombin. An enzyme complex, thrombokinase, is required
for the above reaction. This complex is formed by a series of linked
enzymic reactions (cascade process) involving a number of factors
present in the plasma in an inactive state. An injury or a trauma
stimulates the platelets in the blood to release certain factors which
activate the mechanism of coagulation. Certain factors released by
the tissues at the site of injury also can initiate coagulation. Calcium
ions play a very important role in clotting.
