Blood

Introduction
Blood is a fluid connective tissue. It circulates constantly around the body,
allowing constant communication between tissues distant from each
other.
It transports:
• oxygen
• nutrients
• hormones
• heat
• protective substances
• clotting factors.

Blood
Blood is composed of a clear, straw-colored, watery fluid called plasma
in which several different types of blood cell are suspended.
Plasma normally constitutes 55% of the volume of blood and the cell
fraction.
Blood makes up about 7% of body weight (about 5-6 liters in a 70 kg
man).
This proportion is less in women and considerably greater in children,
gradually decreasing until the adult level is reached.

Characteristics
Blood Volume: 5-6 Liters
Normal Reaction: Slightly Alkaline pH 7.35-7.45
Specific Gravity: 1.052-1.060
Viscosity: 4-5 Times More Than Water
Temperature: 36-380C
Osmotic Pressure: 25mmHg
Color: bright Red(oxygenated); dark red/purplish(deoxygenated)
Taste: Salty

Composition
Cellular substance: 45%
44% RBC & 1% buffy coat containing platelets and WBC
Plasma(fluid): 55%
91-92% water
8-9% solid
Organic Substances: proteins, carbohydrates, fat, urea,
uric acid, creatine, ammonia, enzymes,
antibodies, hormones, bilirubin, etc
Inorganic Substances: sodium, potassium, calcium,
magnesium, phosphorous, iron, copper, etc

Plasma
The constituents of plasma are water (90–92%) and dissolved and
suspended substances, including:
• plasma proteins
• inorganic salts
• nutrients, principally from digested foods
• waste materials
• hormones
• gases.

Plasma proteins
Plasma proteins, which make up about 7% of plasma, are normally retained
within the blood, because they are too big to escape through the capillary
pores into the tissues.
They are largely responsible for creating the osmotic pressure of blood,
which keeps plasma fluid within the circulation.
Plasma viscosity (thickness) is due to plasma proteins, mainly albumin and
fibrinogen.
Plasma proteins, with the exception of immunoglobulins, are formed in the
liver.

Important plasma proteins are
Albumin
Globulin
Fibrinogen
Prothrombin

Functions of plasma protein
They transport hormones, iron and other substances.
They exert osmotic pressure and regulate blood volume.
They provide viscosity to blood(which helps in maintaining
blood pressure).
Fibrinogen in plasma in necessary for clotting
Globulin of plasma is important for the synthesis of immune
substances called antibodies.

Electrolytes
These have a range of functions, including muscle contraction
(e.g. Ca2
+), transmission of nerve impulses (e.g. Ca2
+ and Na+),
and maintenance of acid–base balance.

Nutrients
The products of digestion, e.g. glucose, amino acids, fatty acids and
glycerol, are absorbed from the alimentary tract.
Together with mineral salts and vitamins they are used by body cells
for energy, heat, repair and replacement, and for the synthesis of
other blood components and body secretions.

Waste products
Urea, creatinine and uric acid are the waste products of protein
metabolism.
They are formed in the liver and carried in blood to the kidneys for
excretion.
Carbon dioxide from tissue metabolism is transported to the lungs
for excretion.

Hormones
These are chemical messengers synthesized by endocrine glands.
Hormones pass directly from the endocrine cells into the blood,
which transports them to their target tissues and organs
elsewhere in the body, where they influence cellular activity.

Gases
Oxygen, carbon dioxide and nitrogen are transported round the body
dissolved in plasma.
Oxygen and carbon dioxide are also transported in combination with
hemoglobin in red blood cells.
Most oxygen is carried in combination with hemoglobin and most
carbon dioxide as bicarbonate ions dissolved in plasma.
Atmospheric nitrogen enters the body in the same way as other gases
and is present in plasma but it has no physiological function.

Cellular Content Of Blood
There are three types of blood cell
• erythrocytes (red blood cells)
• thrombocytes (platelets)
• leukocytes (white blood cells).
Blood cells are synthesized mainly in red bone marrow. Some
lymphocytes, additionally, are produced in lymphoid tissue. In the bone
marrow, all blood cells originate from pluripotent (i.e. capable of
developing into one of a number of cell types) stem cells and go through
several developmental stages before entering the blood. Different types of
blood cell follow separate lines of development.
The process of blood cell formation is called hemopoiesis

Erythrocytes (Red Blood Cells)
Red blood cells are by far the most abundant type of blood cell; 99%
of all blood cells are erythrocytes.
They are biconcave discs with no nucleus, and their diameter is about
7 μm.
Their main function is in gas transport, mainly of oxygen, but they
also carry some carbon dioxide.

Their characteristic shape is suited to their purpose; the biconcavity
increases their surface area for gas exchange, and the thinness of the
central portion allows fast entry and exit of gases.
The cells are flexible so they can squeeze through narrow capillaries, and
contain no intracellular organelles, leaving more room for hemoglobin,
the large pigmented protein responsible for gas transport.

Because they have no nucleus, erythrocytes cannot divide and so need to
be continually replaced by new cells from the red bone marrow, which is
present in the ends of long bones and in flat and irregular bones.
They pass through several stages of development before entering the
blood.
Their life span in the circulation is about 120 days.
There are approximately 30 trillion (1014) red blood cells in the average
human body, about 25% of the body’s total cell count, and around 1%,
mainly older cells, are cleared and destroyed daily.

Red Blood Cells(Erythrocytes)
Can be deformed into any shape
• Excess cell membrane
• Less tendency of rupture
• Can squeeze through capillaries

Functions of RBC:
 Transport oxygen from lungs to tissue.
 Transport carbon dioxide from tissue to lungs.
 Hemoglobin in RBC Functions as good buffer
 Carry the blood group antigens like A Agglutinogen, B Agglutinogen,
and Rh factor. This helps in determining blood group and blood
transfusion.

Red Blood Cells
Sites of Production
Yolk sac- fetus less than 2 months
Liver: 2-5 months
Spleen: 2-5 months
Lymph nodes: adult life
Bone marrows: adult life

Development Of Erythrocytes
Formed in bone marrow
The process of development of red
blood cells from stem cells takes about 7
days and is called erythropoiesis.
The immature cells are released into the
bloodstream as reticulocytes, and
mature into erythrocytes over a day or
two within the circulation. During this
time, they lose their nucleus and
therefore become incapable of division.

Development Of Erythrocytes
Both vitamin B12 and folic acid are
required for red blood cell synthesis.
They are absorbed in the intestines,
although vitamin B12 must be bound
to intrinsic factor to allow
absorption to take place. Both
vitamins are present in dairy
products, meat and green
vegetables.
The liver usually contains
substantial stores of vitamin B12,
several years’ worth, but signs of
folic acid deficiency appear within a
few months

Control Of Erythropoiesis: The Role Of Erythropoietin

Hemoglobin
hemoglobin is a large, complex
molecule containing a globular protein
(globin) and a pigmented iron-
containing complex called hem.
Each hemoglobin molecule contains
four globin chains and four hem units,
each with one atom of iron. As each
atom of iron can combine with an
oxygen molecule, this means that a
single hemoglobin molecule can carry
up to four molecules of oxygen.

Hemoglobin
An average red blood cell carries about 280 million hemoglobin
molecules, giving each cell atheoretical oxygen-carrying capacity of over a
billion oxygen molecules.
Iron is carried in the bloodstream bound to its transport protein,
transferrin, and stored in the liver.
Normal red cell production requires a steady supply of iron.
Absorption of iron from the alimentary canal is very slow, even if the diet
is rich in iron, meaning that iron deficiency can readily occur if losses
exceed intake.

Types Of Hemoglobin
Oxyhemoglobin: It is the combined form of oxygen and hemoglobin
which is found in arterial blood and is the oxygen carried to the body
tissue.
Methemoglobin: A compound formed from hemoglobin by oxidation of
its ferrous iron to ferric iron by injury or toxic substance.
Carboxyhemoglobin: The inhaled carbon monoxide combines with
hemoglobin binding more tightly then oxygen and rendering the
hemoglobin incapable of transporting oxygen is known as
carboxyhemoglobin.

Functions Of Hemoglobin
It transports respiratory gases(oxygen and carbon dioxide).
Maintenance of acid base balance.
It reserves iron and protein.

Erythrocyte Disorder
Polycythemia is excess of RBC.
Primary polycythemia is due to cancer of myeloid tissue.
Secondary polycythemia is caused by lung damage, high altitude
or other factors leading to hypoxia.

Erythrocyte Disorder
Anemia is deficiency of either RBC or hemoglobin.
Anemia falls into three categories:
inadequate erythropoiesis or hemoglobin production
hemorrhagic anemia from bleeding and
hemolytic anemia from RBC destruction.
Three potential consequences of anemia are
Hypoxia
reduced blood osmolarity and
reduced blood viscosity.

Leukocytes (White Blood Cells)
These cells have an important function in defense and immunity.
They detect foreign or abnormal (antigenic) material and destroy it,
through a range of defense mechanisms.
Leukocytes are the largest blood cells but they account for only about
1% of the blood volume.
They contain nuclei and some have granules in their cytoplasm.

Leukocytes (White Blood Cells)
There are two main types:
Granulocytes (Polymorphonuclear Leukocytes) :
Neutrophils
Eosinophils
Basophils
Agranulocytes:
Monocytes
Lymphocytes
Rising white cell numbers in the bloodstream usually indicate a physiological
problem, e.g. infection, trauma or malignancy.

Leucocytes(White Blood Cells)
Life span
Granulocytes: 4-8 hrs in blood, 4-5 days in tissue
Monocytes: 10-20 hrs in blood, months in tissue
Lymphocytes: circulates continually, weeks to months

Leucocytes (White Blood Cells)

Granulocytes
All granulocytes have multilobed nuclei in their cytoplasm.
Their names represent the dyes they take up when stained in the laboratory.
Eosinophils take up the red acid dye, eosin;
basophils take up alkaline methylene blue; and
neutrophils are purple because they take up both dyes.

Eosinophils
Eosinophils, although capable of phagocytosis, are less active in this
than neutrophils; their specialized role appears to be in the elimination
of parasites, such as worms, which are too big to be phagocytosed.
They are equipped with certain toxic chemicals, stored in their
granules, which they release when the eosinophil binds to an infecting
organism.
Local accumulation of eosinophils may occur in allergic inflammation,
such as the asthmatic airway and skin allergies.

Neutrophils
These small, fast and active scavengers protect the body against bacterial
invasion, and remove dead cells and debris from damaged tissues.
They are attracted in large numbers to any area of infection by chemicals called
chemotaxins, released by damaged cells.
Their numbers rise very quickly in an area of damaged or infected tissue. Once
there, they engulf and kill bacteria by phagocytosis.
Neutrophils live on average 6–9 hours in the bloodstream.
Pus that may form in an infected area consists of dead tissue cells, dead and live
microbes, and phagocytes killed by microbes.

Phagocytic Action Of Neutrophils.

Basophils
Basophils, which are closely associated with allergic reactions,
contain cytoplasmic granules packed with heparin (an
anticoagulant), histamine (an inflammatory agent) and other
substances that promote inflammation.
Usually the stimulus that causes basophils to release the contents
of their granules is an allergen (an antigen that causes allergy) of
some type.

Neutrophils:
Protect against any foreign materials that gains entry to the body
To remove waste materials
Eosoniphils
Elimination of parasites
Often found at sites of allergic inflammation
Basophils:
Closely associated with allergic reaction
Packed with heparin, histamine, etc

Agranulocytes
The monocytes and lymphocytes make up 25 to 50% of the
total leukocyte count.
They have a large nucleus and no cytoplasmic granules.

Monocytes:
These are the largest of the white blood cells.
Some circulate in the blood and are actively motile and phagocytic
while others migrate into the tissues where they develop into
macrophages.

Monocytes:
Both types of cell produce interleukin 1, which:
acts on the hypothalamus, causing the rise in body temperature
associated with microbial infections
stimulates the production of some globulins by the liver
enhances the production of activated T-lymphocytes.
Macrophages have important functions in inflammation and
immunity.

Lymphocytes:
Smaller than monocytes and have large nucleus
Some circulate in the blood but most are found in tissues,
including lymphatic tissue such as lymph nodes and the spleen.
Responds to antigens
Two distinct types: T- lymphocytes & B- lymphocytes

Disorders of Leukocytes
Leukopenia is a condition in which too few leukocytes are produced.
If this condition is pronounced, the individual may be unable to ward
off disease.
Excessive leukocyte proliferation is known as leukocytosis.
Although leukocyte counts are high, the cells themselves are often
nonfunctional, leaving the individual at increased risk for disease.

Leukemia is a cancer involving an abundance of leukocytes.
It may involve only one specific type of leukocyte from either the
myeloid line (myelocytic leukemia) or the lymphoid line (lymphocytic
leukemia).
In chronic leukemia, mature leukocytes accumulate and fail to die.
In acute leukemia, there is an overproduction of young, immature
leukocytes. In both conditions the cells do not function properly.

Lymphoma is a form of cancer in which masses of malignant T and/or
B lymphocytes collect in lymph nodes, the spleen, the liver, and other
tissues.
As in leukemia, the malignant leukocytes do not function properly,
and the patient is vulnerable to infection.
Some forms of lymphoma tend to progress slowly and respond well
to treatment. Others tend to progress quickly and require aggressive
treatment, without which they are rapidly fatal.

Functions Of Leucocytes(WBC)
Protection against infection: done by neutrophils and monocytes by
phagocytosis.
To aid in repair of injured tissue.
To produce immune substances which defense against disease. This is
done by lymphocytes through synthesis of gamma globulin.
Basophils secretes an anticoagulant substance called heparin.

Platelets (Thrombocytes)
These are very small discs, 2–4 μm in diameter,
derived from the cytoplasm of megakaryocytes
in red bone marrow.
Although they have no nucleus, their cytoplasm
is packed with granules containing a variety of
substances that promote blood clotting, which
causes hemostasis (cessation of bleeding).

Thrombocytes(platelets)
The life span of platelets is between 7 and 14
days and those not used in hemostasis are
destroyed by macrophages, mainly in the
spleen.
About a third of platelets are stored within the
spleen rather than in the circulation; this is an
emergency store that can be released as
required to control excessive bleeding.

Platelets are derived from cells called megakaryocytes.

Functions Of Platelet
Platelets are essential parts of blood coagulating mechanism.
They close minute lesions in the walls of vessels.
Helps in clot retraction.
By the property of agglutination, platelets encircle the foreign bodies
and kill them by process of phagocytosis.

Disorders of Platelets
Thrombocytosis is a condition in which there are too many platelets.
This may trigger formation of unwanted blood clots (thrombosis), a
potentially fatal disorder.
If there is an insufficient number of platelets, called
thrombocytopenia, blood may not clot properly, and excessive
bleeding may result.

Functions of Blood
Carries respiratory gases, nutrients, hormones, enzymes, vitamins,
metabolites(body fluid, CSF) other chemicals and wastes
Regulates body temperature
Maintains water and electrolyte balance
Maintains acid base balance
Contains agents which protects against infection
Coagulation of blood by platelets.

Product And Functions Of Blood Cells
SN Cell type Normal count Life span Main product or component Main function
1. Erythrocyte M: 47-61 lakh/mm3
F: 42-54 lakh/mm3
120 days Hemoglobin Gaseous transport(CO2 and O2)
2. Leucocytes 4000-11000/mm3 1-14 days To provide immunity
2.1 Neutrophil 1000-6000/mm3 1-5 days Azurophilic granule Phagocytosis of bacteria
2.2 Eosinophil 150-450/mm3 7- 12
days
Specific granules with modified
lysozyme
Defense against parasitic
helminth; modulation of
inflammatory process
2.3 Basophil 0-10/mm3 12-15
days
Granules containing histamine
heparin
Release of histamine and other
inflammation mediators
2.4 Monocyte 200-600/mm3 5-8 days Lysosomal enzyme Phagocytosis and digestion of
protozoa and virus infected cells
2.5 Lymphocyte 1500-2700/mm3 ½-1day
a. T-lymphocyte 2days Interleukins Killing of virus infected cells
b. B- lymphocyte 1 day Immunoglobulins Generation of antibody- producing
terminal cells
c. Natural killer
(NK) cells
1day Attacks virus infected& cancer
cells without previous stimulation
Killing of some tumor and virus
infected cells
3. Platelet 1.5 - 4 lakh/mm3 7-14 days Blood clotting substance Clotting of blood

Blood Cells Count
RBC count
4.7-6.1 million/mm3 in male
4.2-5.4 million/mm3 in female
WBC count
4000-11000/mm3
Platelets
1,50,000- 4,00,000/mm3
Hemoglobin
12-16gm/dl for female
14-18gm/dl for male

Blood is composed of straw colored transparent fluid when blood cells are
suspended. It is called
I. Serum
II. Plasma
III. Hemocrit
IV. Fibrinogen
Viscosity of blood is mainly due to
I. RBCs
II. WBCs
III. Platelets
IV. Electrolytes
Approximate life span of platelet is:
I. 120 days
II. 7 days
III. 24 hrs
IV. 6 hrs

Formation of blood
The process of formation of blood is hemopoiesis.
Sites Of Blood Formation:
During intrauterine life:
yolk sac (1-2 months)
liver and spleen (2-5months)
bone marrow, lymph node, spleen (5months till birth)
After birth:
Bone marrow, lymph node, spleen

Blood Grouping(Rhesus/Rh System)
Blood group RBC Antigen Antibody Frequency
Positive D None 85%
Negative None None by birth 15%

Prevalence Of Different Blood Group

Parents Child Blood Group Relationship

Purpose Of Blood Grouping
Blood transfusion: if non match blood will be transferred to the
patient then there will be antigen antibody reaction and hemolysis
will occur.
To prevent hemolytic disease of new born.
Relationship of blood groups, susceptibility to various diseases.

Basis Of Transfusion Reaction
Individual have different types of antigen on the surface of their RBCs.
These antigens, which are inherited, determine the individual’s blood
group .
Individuals can make antibodies to these antigens, but not to their own
type of antigen, since if they did the antigens and antibodies would
react, causing a potentially fatal transfusion reaction.
These antibodies circulate in the blood stream and the ability to make
them, like the antigens, is genetically determined and not associated
with acquired immunity.

Basis Of Transfusion Reaction
If individuals are transfused with blood of the same group, i.e.
possessing the same antigens on the surface of the cells, their immune
system will not recognize them as foreign and will not reject them.
However, if they are given blood from an individual of a different blood
type, i.e. with a different type of antigen on the red cells, their immune
system will generate antibodies to the foreign antigens and destroy the
transfused cells.
This is the basis of the transfusion reaction; the two blood types, the
donor and the recipient, are incompatible.

Hemostasis
The process which causes stoppage of bleeding is called
hemostasis.
It keeps blood within a damaged blood vessel hence prevent
bleeding.
The opposite of hemostasis is hemorrhage.
It is the first stage of wound healing.

Steps Of Hemostasis:
1. Vasoconstriction
2. Platelet plug formation
3. Coagulation(blood clotting)
4. Fibrinolysis

Vasoconstriction:
Platelet come in contact with damaged blood vessel
become sticky
adhere to the wall
release serotonin
constrict blood vessel
reduce blood flow

Platelet Plug Formation:
Adherent platelet clump to each other
release ADP
attracts more platelets
forms temporary seal-platelet plug

Coagulation
Prothrombin activator can be formed by
two process: the extrinsic and intrinsic
pathway.
The extrinsic pathway is activated rapidly
(within seconds) following tissue damage.
Damaged tissue releases a complex of
chemicals called thromboplastin or tissue
factor, which initiates coagulation.
The intrinsic pathway is slower (3–6
minutes) and is triggered when blood
comes into contact with damaged blood
vessel lining (endothelium) and the
effects of platelets adhering to it.

Coagulation
Blood clotting results in the formation of
insoluble thread like mesh of fibrin which
traps the blood cells and is much
stronger than the rapidly formed platelet
plug.
In the final stage of this process
prothrombin activator acts on the
plasma protein prothrombin converting
it to thrombin.
Thrombin acts on another plasma
protein fibrinogen and converts it to
fibrin.

Fibrinolysis:
The breakdown of clot is called fibrinolysis.
An inactive substance called plasminogen is present in clot and is
converted to the enzyme plasmin by activators released from the
damaged endothelial cells.
Plasmin initiates breakdown of fibrin to soluble products that are
treated as waste materials and are removed by phagocytosis.

Erythroblastosis Fetalis
It is a clinical condition, if Rh –ve mother has Rh +ve fetus, at the time of
delivery fetal RBCs enter maternal circulation and cause sensitization
leading to formation of agglutin against Rh in large quantity.
If next time this woman becomes pregnant and bears Rh +ve fetus,
agglutin can enter from mother to fetus leading to agglutination of fetal
RBC and hemolysis. Severe hemolysis in fetus causes jaundice.

Erythroblastosis Fetalis
To compensate hemolysis more and more number of RBC are needed
not only from bone marrow but also from liver and spleen.
Now many large and immature proerythroblastic stage are released in
circulation because of this only disease is called erythroblastosis fetalis.
Ultimately due to excessive hemolysis anemia occurs and the infant
dies because of severe anemia.

Donated blood should be used within
I. 4 weeks
II. 4 months
III. 10 weeks
IV. 10 months
Which blood group is called universal receiver
I. A
II. B
III. AB
IV. O
Universal donar is one who has blood group
I. A
II. B
III. AB
IV. O

In blood group A there is:
I. No antibodies, A&B antigen
II. Anti-B antibody, A antigen
III. Anti-A antibody, B antigen
IV. Anti-A & anti-B antibody, no antigen
Donated blood is usually taken from
I. Artery
II. Vein
III. Capillary
IV. artery and vein

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