Table Of ConteNt

S.No. Topics Page No.

1. Introduction 2

2. Blood 3

3. Composition Of Blood 4

4. History Of Blood Types 9

5. Importance Of Antibodies 10

6. Importance Of Antigens 11

7. Chemistry Of Blood Group Substances 11

8. Types Of Blood – Blood Grouping System 12

9. Rh Factor 14

10. Importance Of Blood Groups In Blood 15

Transfusions

11. Blood Groups And Populations 17

12. Conclusion 18

13. Bibliography 18

1
 Introduction
Blood, often referred to as the "river of life", is a remarkable fluid that
courses through the human body, ensuring the delivery of essential
nutrients, oxygen, and vital components to every tissue and organ.
More than just a liquid, blood is a complex mixture, comprised of
various cellular and plasma components, each playing a distinct role
in maintaining our health and well-being.
At its core, blood is a symphony of cells suspended in a liquid matrix
called plasma. The cellular elements, including red blood cells, white
blood cells, and platelets, collaborate with plasma to facilitate a
myriad of functions, from oxygen transport to immune defence and
clotting mechanisms.

However, not all blood is identical. One of the most intriguing aspects
of blood is its classification into different groups, primarily
determined by the presence or absence of specific antigens on the
surface of red blood cells. These classifications, known as blood
groups or blood types, have profound implications, especially in
medical procedures like transfusions and organ transplants. The ABO
system, the most familiar blood group classification, categorizes
blood into types A, B, AB, and O, each with its unique antigenic
profile and compatibility characteristics.

2
 Blood
Blood is a body fluid in the circulatory system of humans and
other vertebrates that delivers necessary substances such
as nutrients and oxygen to the cells, and transports metabolic waste
products away from those same cells. Blood in the circulatory system
is also known as peripheral blood, and the blood cells it
carries, peripheral blood cells.

Blood is composed of blood cells suspended in blood plasma. Plasma,

which constitutes 55% of blood fluid, is mostly water (92% by
volume), and contains proteins, glucose,
mineral ions, hormones, carbon dioxide (plasma being the main
medium for excretory product transportation), and blood cells
themselves. Albumin is the main protein in plasma, and it functions to
regulate the colloidal osmotic pressure of blood. The blood cells are
mainly red blood cells (also called RBCs or erythrocytes), white
blood cells (also called WBCs or leukocytes), and in
mammals platelets (also called thrombocytes). The most abundant
cells in vertebrate blood are red blood cells. These
contain haemoglobin, an iron-containing protein, which facilitates
oxygen transport by reversibly binding to this respiratory gas thereby
increasing its solubility in blood. In contrast, carbon dioxide is mostly
transported extracellularly as bicarbonate ion transported in plasma.

3
 Composition Of Blood
Plasma
This is the liquid component of blood, making up about 55% of its
volume. Plasma is primarily water (about 90%) and contains:
 Proteins: Albumin, globulins (including antibodies), and
fibrinogen.
 Nutrients: Glucose, amino acids, and fatty acids.
 Waste products: Urea, creatinine, and uric acid.
 Electrolytes: Sodium, potassium, calcium, magnesium,
chloride, bicarbonate, and phosphate.]

Blood Cells

4
 These are cellular components that make up about 45% of blood
volume and include:

Red Blood Cells (Erythrocytes)

RBCs are biconcave cells without nucleus in humans; also known as
erythrocytes. RBCs contain the iron-rich protein called haemoglobin;
give blood its red colour. RBCs are the most copious blood cells
produced in bone marrows. Their main function is to transport oxygen
from and to various tissues and organs.

White Blood Cells

(Leucocytes)
Leucocytes are colourless blood cells. They are colourless because it
is devoid of haemoglobin. They are further classified as granulocytes
and agranulocytes. WBCs mainly contribute to immunity and defence
mechanism.

Types Of White Blood Cells:-

5
There are five different types of White blood cells and are classified
mainly based on the presence and absence of granules.
 Granulocytes
 Agranulocytes

Granulocytes:-

They are leukocytes, with the presence of granules in their cytoplasm.

The granulated cells include- eosinophil, basophil, and neutrophil.
Eosinophils:
 They are the cells of leukocytes, which are present in the
immune system.
 These cells are responsible for combating infections in parasites
of vertebrates and for controlling mechanisms associated with
allergy and asthma.
 Eosinophil cells are small granulocyte, which are produced in
the bone marrow and makes 2 to 3 per cent of whole WBCs.
These cells are present in high concentrations in the digestive
tract.
Basophils:

6
  They are the least common of the granulocytes, ranging from
0.5 to 1 per cent of WBCs.
 They contain large cytoplasmic granules, which play a vital role
in mounting a non-specific immune response to pathogens, and
allergic reactions by releasing histamine and dilating the blood
vessels.
 These white blood cells have the ability to be stained when
exposed to basic dyes, hence referred to as basophil.
 These cells are best known for their role in asthma and their
result in inflammation and bronchoconstriction in the airways.
 They secrete serotonin, histamine and heparin.
Neutrophils:
 They are normally found in the bloodstream.
 They are predominant cells, which are present in pus.
 Around 60 to 65 per cent of WBCs are neutrophils with a
diameter of 10 to 12 micrometres.
 The nucleus is 2 to 5 lobed and the cytoplasm has very fine
granules.
 Neutrophil helps in the destruction of bacteria with lysosomes,
and it acts as a strong oxidant.
 Neutrophils are stained only using neutral dyes. Hence, they are
called so.
 Neutrophils are also the first cells of the immune system to
respond to an invader such as a bacteria or a virus.
 The lifespan of these WBCs extends for up to eight hours and is
produced every day in the bone marrow.

Agranulocytes:-
They are leukocytes, with the absence of granules in their cytoplasm.
Agranulocytes are further classified into monocytes and lymphocytes.
Monocytes:

7
  These cells usually have a large bilobed nucleus, with a
diameter of 12 to 20 micrometres.
 The nucleus is generally half-moon shaped or kidney-shaped
and it occupies 6 to 8 per cent of WBCs.
 They are the garbage trucks of the immune system.
 The most important functions of monocytes are to migrate into
tissues and clean up dead cells, protect against bloodborne
pathogens and move very quickly to the sites of infections in
the tissues.
 These white blood cells have a single bean-shaped nucleus,
hence referred to as Monocytes.
Lymphocytes:
 They play a vital role in producing antibodies.
 Their size ranges from 8 to 10 micrometres.
 They are commonly known as natural killer cells.
 They play an important role in body defence.
 These white blood cells are colourless cells formed in lymphoid
tissue, hence referred to as lymphocytes.
 There are two main types of lymphocytes – B lymphocytes and
T lymphocytes.
 These cells are very important in the immune systems and are
responsible for humoral and cell-mediated immunity.

8
 Platelets (Thrombocytes)
 Thrombocytes are specialized blood cells produced from bone
marrow.
 Platelets come into play when there is bleeding or haemorrhage.
 They help in clotting and coagulation of blood. Platelets help in
coagulation during a cut or wound.

History Of Blood Types

It was in 1901, that Austrian-American
immunologist and pathologist Karl
Landsteiner discovered human blood
groups. Karl Landsteiner's work helps
to determine blood groups and thus
opened a way for blood transfusions
which can be carried out safely. He
was awarded the Nobel Prize in
Physiology or Medicine in 1930 for
this discovery. He recognized three
groups—A, B, and O—based on their
reactions to each other.

9
A fourth group, AB, was identified a year later by another research
team. Other blood groups were identified later, such as, Diego,
Lutheran, Duffy, and Kidd. The remaining blood group systems were
rest described after antibodies were identified in patients. Once
reliable tests for Rhesus grouping had been established, transfusion
reactions became rare! For this discovery Landsteiner was awarded
the Nobel Prize in Physiology or Medicine in 1930.

Importance Of Antibodies
Antibodies are part of the circulating plasma proteins known as
immunoglobulins, which are classified by molecular size and weight
and by several other biochemical properties. Most blood group
antibodies are found either on immunoglobulin G or immunoglobulin
M molecules, but occasionally the immunoglobulin A class may
exhibit blood group specificity. Naturally occurring antibodies are the
result of immunization by substances in nature that have structures
similar to human blood groups. These antibodies are present in an
individual despite the fact that there has been no previous exposure to
the corresponding red cell antigens—for example, anti-A in the
plasma of people of blood group B and anti-B in the plasma of people
of blood group A.

10
 Importance Of Antigens
The red cells of an individual contain antigens on their surfaces that
correspond to their blood group and antibodies in the serum that
identify and combine with the antigen sites on the surfaces of red cells
of another type. Individual blood group antigens vary in their
antigenic potential; for example, some of the antigens belonging to
the Rh and ABO systems are strongly immunogenic (i.e., capable of
inducing antibody formation), whereas the antigens of the Kidd and
Duffy blood group systems are much weaker immunogens. The
blood group antigens are not restricted solely to red cells or even to
hematopoietic tissues. The antigens of the ABO system are widely
distributed throughout the tissues and have been unequivocally
identified on platelets and white cells and in skin, the epithelial cells
of the gastrointestinal tract, the kidney, the urinary tract, and the
lining of the blood vessels. Evidence for the presence of the antigens
of other blood group systems on cells other than red cells is less well
substantiated. Among the red cell antigens, only those of the ABO
system are regarded as tissue antigens and therefore need to be
considered in organ transplantation.

Chemistry Of Blood Group Substances

The exact chemical structure of some blood groups has been
identified, as have the gene products (i.e., those molecules
synthesized as a result of an inherited genetic code on a gene of a
chromosome) that assist in synthesizing the antigens on the red cell
surface that determine the blood type. Blood group antigens are
present on glycolipid and glycoprotein molecules of the red cell
membrane. The carbohydrate chains of the membrane glycolipids are
oriented toward the external surface of the red cell membrane and
carry antigens of the ABO, Ii, and P systems
11
 Types Of Blood – Blood Grouping System
The ABO blood group system is based on the presence or absence of
specific antigens on the surface of red blood cells (RBCs) and the
presence of corresponding antibodies in the plasma. The system
categorizes blood into four main types: A, B, AB, and O.

From the above mentioned table it is evident that group O blood can
be donated to persons with any other blood group and hence O group
individuals are called ‘UNIVERSAL DONORS’. Persons with AB
group can accept blood from persons with AB as well as the other
groups of blood. Therefore, such persons are called ‘UNIVERSAL
RECIPIENTS’. According to the AB0 blood group system there are
four different kinds of blood groups: A, B, AB and O.

Blood Group A:
Antigens: Contains A antigens on the surface of
RBCs.
Antibodies: Produces anti-B antibodies in the plasma.
Compatibility: Can donate to A and AB; can receive from A and O.

12
Blood Group B:
Antigens: Contains B antigens on the surface of
RBCs.
Antibodies: Produces anti-A antibodies in the plasma.
Compatibility: Can donate to B and AB; can receive from B and O.

Blood Group AB:

Antigens: Contains both A and B antigens on the
surface of RBCs.
Antibodies: Lacks both anti-A and anti-B antibodies
in the plasma.
Compatibility: Universal recipient (can receive from A, B, AB, and
O); can donate only to AB.

Blood Group O:
Antigens: Lacks both A and B antigens on the surface
of RBCs.
Antibodies: Produces both anti-A and anti-B
antibodies in the plasma.
Compatibility: Universal donor (can donate to A, B, AB, and O); can
receive only from O.

13
 Rh Factor
Another antigen, the RH antigen (often
referred to as the "D" antigen). similar to
one present in Rhesus Monkeys, is also
observed on the surface of RBC’s of
majority of humans. Such individuals are
called RH Positive and those in whom this
antigen is absent are called RH Negative.
An RH negative person, if exposed to RH
Positive blood, will form specific antibodies against the RH antigens.
Therefore, RH group should also be matched before transfusions. The
Rh factor becomes particularly crucial during pregnancy. If an Rh-
negative mother carries an Rh-positive foetus, there's a risk of Rh
incompatibility, which can lead to complications in subsequent
pregnancies if not managed appropriately.

 Rh-positive (Rh+): Has the Rh antigen on the RBCs.

 Rh-negative (Rh-): Lacks the Rh antigen.

14
Importance Of Blood Groups In Blood Transfusions
Compatibility:
 Blood transfusions involve transferring blood from a donor to a
recipient. For the transfusion to be successful and not harm the
recipient, the donor and recipient blood types must be
compatible.
 Mismatched blood transfusions can result in severe and
potentially life-threatening reactions, such as hemolytic
transfusion reactions, where the recipient's immune system
attacks and destroys the donor's red blood cells.

ABO Blood Group System:

 The ABO system categorizes blood into four main types: A, B,

AB, and O. Understanding these blood types is essential for
ensuring compatibility during transfusions.
 For example, someone with blood type A can typically receive
blood from donors with type A or O but not from type B or AB
donors due to the presence of incompatible antibodies in the
recipient's plasma.

Rh Factor:

 In addition to the ABO system, the Rh (Rhesus) system plays a

crucial role in blood transfusions. The presence or absence of
the Rh antigen (Rh-positive or Rh-negative) must be considered,
especially in Rh-negative individuals, to prevent potential Rh
incompatibility reactions.

15
  Rh incompatibility is particularly significant in certain
scenarios, such as during pregnancy, where an Rh-negative
mother carrying an Rh-positive foetus can lead to complications
in subsequent pregnancies if not managed appropriately

Reducing Risks:

 Properly matching blood types and conducting compatibility

tests before transfusions significantly reduce the risk of adverse
reactions and complications.
 Blood banks and transfusion services employ rigorous testing
and screening protocols to ensure the safety of donated blood
and match it appropriately with recipients.

Optimizing Efficacy:

 Ensuring compatibility between donor and recipient blood types

not only minimizes risks but also optimizes the efficacy of
transfusions. Compatible transfusions provide the intended
therapeutic benefits, such as delivering oxygen to tissues and
supporting vital functions, without triggering harmful immune
responses.

Understanding blood types is vital in medical scenarios, especially

during blood transfusions. Mismatched blood transfusions can lead to
potentially life-threatening reactions, making it essential to ensure
compatibility between donor and recipient blood types.

16
Blood Groups And Populations

17
 Conclusion
In summary, blood types, primarily determined by the ABO and Rh
systems, play a pivotal role in medical practices, from transfusions to
organ transplants, underscoring the significance of understanding and
classifying blood based on its unique characteristics.

18
 Bibliography

Reference Books:-
 NCERT Textbook

 NCERT Biology Lab Manual

 Oswaal Biology Packages

 Aakash + Byju’s Biology Packages

Online Resources:-
 https://www.medicalnewstoday.com

 https://www.wikipedia.com

 https://www.icbse.com

 https://www.google.com

19
20