The document discusses the composition and functions of blood. It describes the components of blood including plasma, red blood cells, white blood cells, and platelets. It explains the process of hematopoiesis where blood cells are produced in the bone marrow. It details the characteristics and functions of red blood cells, white blood cells, and platelets. It also outlines the mechanism of blood clotting through the coagulation cascade.

1. 5.
Haemopoietic system
Composition and functions of blood
Process of Hematopoiesis
Characteristics and functions of RBCs,
WBCs and platelets
Mechanism of Blood Clotting
Importance of Blood groups

2. Composition and functions of blood
Blood is a fluid connective tissue that consists of plasma, blood
cells and platelets. It circulates throughout our body delivering
oxygen and nutrients to various cells and tissues. It makes up
8% of our body weight. An average adult possesses around 5-6
litres of blood.
Components Of Blood
There are many cellular structures in the composition of
blood. When a sample of blood is spun in a centrifuge machine,
they separate into the following constituents: Plasma, buffy coat
and erythrocytes.

5. Plasma
The liquid state of blood can be contributed to plasma as it makes
up ~55% of blood. It is pale yellow in colour and when separated, it
consists of salts, nutrients, water and enzymes. Blood plasma also
contains important proteins and other components necessary for overall
health. Hence, blood plasma transfusions are given to patients with liver
failure and life-threatening injuries.
Red Blood Cells (RBC)
Red blood cells consist of Hemoglobin, a protein. They are produced by
the bone marrow to primarily carry oxygen to the body and carbon
dioxide away from it.
White Blood Cells (WBC)
White blood cells are responsible for fighting foreign pathogens (such as
bacteria, viruses, and fungi) that enter our body. They circulate
throughout our body and originate from the bone marrow.
Platelets
Tiny disc-shaped cells that help regulate blood flow when any part of the
body is damaged, thereby aiding in fast recovery through clotting of
blood.

6. Functions of Blood
Blood is responsible for the following body functions:
Fluid Connective Tissue
Blood is a fluid connective tissue composed of 55% plasma
and 45% formed elements including WBCs, RBCs, and
platelets. Since these living cells are suspended in plasma,
blood is known as a fluid connective tissue and not just fluid.
Provides oxygen to the cells
Blood absorbs oxygen from the lungs and transports it to
different cells of the body. The waste carbon dioxide moves
from the blood to the lungs and is exhaled.
Transports Hormones and Nutrients
The digested nutrients such as glucose, vitamins, minerals,
and proteins are absorbed into the blood through the
capillaries in the villi lining the small intestine.
The hormones secreted by the endocrine glands are also
transported by the blood to different organs and tissues.

7. Homeostasis
Blood helps to maintain the internal body temperature by
absorbing or releasing heat.
Blood Clotting at Site of Injury
The platelets help in the clotting of blood at the site of
injury. Platelets along with the fibrin form clot at the wound
site
Transport of waste to the Kidney and Liver
Blood enters the kidney where it is filtered to remove
nitrogenous waste out of the blood plasma. The toxins from
the blood are also removed by the liver.
Protection of the body against pathogens
The White Blood Cells fight against infections. They
multiply rapidly during infections.

8. Process of Hematopoiesis
• General term for production of blood cells from
Haemopoietic stem cell.
• It includes
• Erytropoiesis
• Leucopoiesis
• Thrombopoiesis

9. Hematopoiesis during the early stages of embryogenesis
occurs in the yolk sac and subsequently in the liver. During
the 3rd to 7th month of gestation it primarily occurs in the
spleen and just before birth shifts to the marrow cavity and
from birth onwards occurs primarily in the bone marrow.
Pluripotent stem cells continuously produce more of
themselves. Hematopoietic cells are constantly generated
from pluripotent stem cells, where some of these pluripotent
cells become unipotential stem cells. Subsequently, some of
the cells of this unipotential population differentiate into
precursor cells that, once differentiated, are in part committed
to becoming one of the mature types of blood cells, which are
erythrocytes, monocytes, lymphocytes, thrombocytes and
granulocytes.

11. Erythropoiesis
Erythropoiesis is the process by which red blood cells, also
known as erythrocytes, are made and are stimulated by
decreased levels of oxygen in the blood, which sets into
motion the secretion of erythropoietin, a hormone central
to the formation of red blood cells. The process of red
blood cell formation takes on average 2 days to be
completed from unipotential hematopoietic cell to mature
red blood cell. In our bodies, there 2 million erythrocytes
are produced every second. Hematopoietic cells committed
to becoming red blood cells usually get smaller and more
condensed as they mature until there is eventually loss of
their nuclei.

12. The unipotential cell becomes what is known as a
proerythroblast, which has a nucleus that is not condensed
and takes up most of the cell with basophilic or blue
cytoplasm. The cell then becomes a basophilic
erythroblast, which is followed by a polychromatophilic
erythroblast stage, where the nucleus is more condensed
than the latter two stages and the cytoplasm becomes
reduced. In the subsequent orthochromatophilic
erythroblast stage, the nucleus is much smaller than that
of the previous stages with a pinker cytoplasm. In the
reticulocyte stage the red blood cell has no nucleus, but
still stains somewhat blue due to the remnants of
polyribosomes within the cell. Finally, the erythrocyte is
the mature red blood cell, which has no nucleus and no
polyribosome remnants and as a result stains pink.

13. Granulopoiesis
Granulopoiesis is the formation of granulocytes, which
are white blood cells with multi-lobular nuclei and
cytoplasmic granules. The unipotential hematopoietic cell
that becomes a myeloblast is large and has a cytoplasm
that stains blue with a large nucleus. This cell evolves into
a promyelocyte that contains azurophilic granules, and
then becomes a myelocyte, which has a non-indented still
rather large nucleus. This cell then becomes a
metamyelocyte, which is similar in size to a mature
granulocyte and the nucleus begins to become indented.
Following this stage is the band cell stage, where the
nucleus has definitive indentation and resembles a
horseshoe. Finally, there is the mature granulocyte, which
has a lobed nucleus and cytoplasmic granules. The entire
process happens over a period of 2 weeks.

14. Monopoiesis, Lymphopoiesis and Thrombopoiesis
Monopoiesis is the process by which monocytes are formed.
The committed progenitor cell, the monoblast, is found only in
the bone marrow and has a basophilic cytoplasm without
granules. These evolve into promonocytes, which are smaller
with nuclei that become slightly indented, before becoming
monocytes, which have kidney-shaped nuclei and can develop
into dendritic cells or macrophages.
Lymphopoiesis is the formation of lymphocytes, which start
from their first committed progenitor cells, lymphoblasts. These
cells go on to mature into lymphocytes that are capable of
differentiating into either B, T or natural killer cells.
Thrombopoiesis is the formation of platelets, which come from
extremely large cells within the bone marrow called
megakaryocytes. The creation of individual platelets occurs
when the plasma membranes of megakaryocytes are fragmented,
thereby generating platelets containing many granules.

15. Characteristics and functions of RBCs, WBCs
and platelets
Red blood cells (Erythrocytes)
RBCs are biconcave cells without nucleus in humans; also known as
erythrocytes. RBCs contain the iron-rich protein called hemoglobin 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.
Erythrocyte structure
Erythrocytes have a consistent diameter of 7-8 µm, However, they have an
atypical structure compared to the majority of human body cells. First of
all, erythrocytes have a biconcave shape, which resembles a donut. This
means that their periphery is thicker than their central part. In addition,
erythrocytes do not have a nucleus (anuclear) or any other
intracellular organelles, as they are all lost during erythropoiesis. The only
two major structures left are the cytoplasm which is enclosed by a
surrounding cell membrane.

16. Cytoplasm
The cytoplasm of RBCs is filled with hemoglobin, a
protein that reversibly binds and transports oxygen and
carbon dioxide.
Hemoglobin is a tetramer that comprises four polypeptide
subunits called globin chains. There are four types of
globin chains (α, β, γ, δ) which can give rise to three main
hemoglobin classes called HbA, HbA2 and HbF.
Cell membrane
The cell membrane of erythrocytes is a lipid bilayer that
contains two types of membrane proteins: integral and
peripheral. Integral membrane proteins are more
numerous, stretching through the entire thickness of the
cell membrane. They bind hemoglobin and serve as anchor
points for the cytoskeletal network of RBCs.

18. Functions of Erythrocytes
• In lung capillaries, hemoglobin binds the inhaled oxygen,
forming oxyhemoglobin. This substance gives
erythrocytes, and hence arterial blood, a bright red colour.
• Oxygen rich erythrocytes then travel through the arteries
until they reach tissue capillaries.
• In tissue capillaries, the oxygen is released from
hemoglobin and diffuses into the tissues.
• Simultaneously, the carbon dioxide from the tissues binds
to hemoglobin, forming deoxyhemoglobin. This substance
gives RBCs, and venous blood, a purple blue colour.
• Carbon dioxide rich erythrocytes then travel via venous
blood towards the heart, and then to the lungs.
• Within lung capillaries, the carbon dioxide is released
from hemoglobin in exchange for a new dose of oxygen.

19. 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
There are five different types of White blood cells and are
classified mainly based on the presence and absence of
granules.
• Granulocytes
• Agranulocytes

20. (A) Granulocytes
They are leukocytes, with the presence of granules in their
cytoplasm. The granulated cells include- eosinophil,
basophil, and neutrophil.
1. 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.

21. 2. Basophils
• 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.
3. 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.

22. (B) Agranulocytes
They are leukocytes, with the absence of granules in their
cytoplasm. Agranulocytes are further classified into monocytes
and lymphocytes.
1. Monocytes
• 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.

23. 2. 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.

25. Platelets (Thrombocytes)
Thrombocytes are specialized blood cells produced from bone
marrow. Platelets, also known as thrombocytes, are special
blood cells. These cells control blood clotting to heal a wound
and stop the bleeding.
Functions of platelets :
• 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.

26. • Adhesion: This is the first step in which platelets rush to the
site that's bleeding. For example, if you cut your finger and
rupture a blood vessel, it will bleed. To stop the blood flow,
platelets within that broken vessel start attaching to the site
of the injury. They then send out chemical signals for more
help.
• Aggregation: In the next step, more platelets answer the
call and begin to connect to each other to form a clot.
• Coagulation: As platelets build up at the site of the wound,
they seal up the blood vessel in what's called a coagulation
cascade. A structural protein known as fibrin joins the
platelets to knit the clot together. Fibrin is what forms the
scab on a cut.

27. Mechanism of Blood Clotting
• Blood coagulation or clotting is an important phenomenon
to prevent excess loss of blood in case of injury or trauma.
The blood stops flowing from a wound in case of injury.
The blood clot or ‘coagulum’ is formed by a network of
fibrin threads. In this network, deformed and dead formed
elements (erythrocytes, leukocytes and platelets) get
trapped.
• Prothrombin is the inactive form of thrombin that is
present in the plasma. Thrombokinase converts
prothrombin to active thrombin which in turn activates
fibrinogen to fibrin. All these clotting factors help in blood
coagulation.
• An injury stimulates platelets or thrombocytes to release
various factors that initiate the blood clotting cascade.
Calcium ions play an important role in blood coagulation.

28. Blood Coagulation Cascade
The process of coagulation is a cascade of enzyme catalysed
reactions wherein the activation of one factor leads to the
activation of another factor and so on.
The three main steps of the blood coagulation cascade are as
follows:
• Formation of prothrombin activator
• Conversion of prothrombin to thrombin
• Conversion of fibrinogen into fibrin

29. 1. Formation of prothrombin activator
The formation of a prothrombin activator is the first step in the blood
coagulation cascade of secondary haemostasis. It is done by two
pathways, viz. extrinsic pathway and intrinsic pathway.
• Extrinsic Pathway
It is also known as the tissue factor pathway. It is a shorter pathway. The
tissue factors or tissue thromboplastins are released from the damaged
vascular wall. The tissue factor activates the factor VII to VIIa. Then the
factor VIIa activates the factor X to Xa in the presence of Ca2+.
• Intrinsic Pathway
It is the longer pathway of secondary haemostasis. It begins with the
exposure of blood to the collagen from the underlying damaged
endothelium. This activates the plasma factor XII to XIIa.
XIIa is a serine protease, it activates the factor XI to XIa. The XIa then
activates the factor IX to IXa in the presence of Ca2+ ions.
The factor IXa in the presence of factor VIIIa, Ca2+ and phospholipids
activate the factor X to Xa.

30. • Common Pathway
The factor Xa, factor V, phospholipids and calcium ions
form the prothrombin activator. This is the start of the
common pathway of both extrinsic and intrinsic pathways
leading to coagulation.
2. Conversion of prothrombin to thrombin
Prothrombin or factor II is a plasma protein and is the
inactive form of the enzyme thrombin. Vitamin K is
required for the synthesis of prothrombin in the liver. The
prothrombin activator formed above converts prothrombin
to thrombin. Thrombin is a proteolytic enzyme. It also
stimulates its own formation, i.e. the conversion of
prothrombin to thrombin. It promotes the formation of a
prothrombin activator by activating factors VIII, V and
XIII.

31. 3. Conversion of fibrinogen into fibrin
Fibrinogen or factor I is converted to fibrin by thrombin.
Thrombin forms fibrin monomers that polymerise to form long
fibrin threads. These are stabilised by the factor XIII or fibrin
stabilising factor. The fibrin stabilising factor is activated by
thrombin to form factor XIIIa. The activated fibrin stabilising
factor (XIIIa) forms cross-linking between fibrin threads in the
presence of Ca2+ and stabilises the fibrin meshwork. The fibrin
mesh traps the formed elements to form a solid mass called a
clot.

33. Importance of Blood groups
• Blood typing is a test that determines a person’s blood type. The
test is essential if need a blood transfusion or planning to
donate blood.
• Not all blood types are compatible, so it’s important to know
your blood group. Receiving blood that’s incompatible with
your blood type could trigger a dangerous immune response.

34. Blood type is determined by what kind of antigens that
red blood cells have on the surface.
Antigens are substances that help the body differentiate
between its own cells and foreign, potentially dangerous
ones. If body thinks a cell is foreign, it will set out to
destroy it.
The ABO blood typing system groups your blood into
one of four categories:
• Type A has the A antigen.
• Type B has the B antigen.
• Type AB has both A and B antigens.
• Type O has neither A nor B antigens.

35. Blood types are further organized by Rh factor:
• Rh-positive: People with Rh-positive blood have Rh antigens
on the surface of their red blood cells. People with Rh-positive
blood can receive Rh-positive or Rh-negative blood.
• Rh-negative: People with Rh-negative blood don’t have Rh
antigens. People with Rh-negative blood can receive only
blood that is also Rh-negative.

36. Importance:
For medical reasons
• The most important reason to know your blood type is in case of an
emergency. If you are in a situation where you require a blood
transfusion, you’ll need compatible blood. An incompatible blood group
can cause blood cells to clump—which can be fatal.
• “Knowing your blood type can also help predict the concentrations of
certain proteins in the bloodstream, like von Willebrand disease” Dr.
Nance said.
To help others
• One of the best, and most selfless, reasons to know your blood type is to
help others through blood donations. Medical facilities are always in
need of blood donations, whether you are O or A.
• “All types of blood are needed because all types of people need blood,”
Dr. Nance said. “Someone needs a blood transfusion every 2 seconds,
according to the American Red Cross. Blood donations are especially
important for people with Native American, Hispanic, African American
and Asian heritage, because blood type in each race is slightly different.”

37. To plan a healthy pregnancy
• Knowing your blood type can help predict some conditions
that can occur during pregnancy, such as Rh
incompatibility between mom and baby.
• “Rh-negative women can become pregnant from an Rh-
positive father,” Dr. Nance said. “When this happens, the
mother can have an immune reaction to the fetus. This
needs to be treated and monitored carefully during
pregnancy.”
To lower risk for certain health conditions
• Most of the time, blood typing helps you safely donate and
help others, but it can also let you know if you are at risk
for certain health conditions in the future. Some
studies suggest connections between certain blood types
and the risk of blood clots and bleeding and kidney stones.

38. THANK YOU