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INTRODUCTION TO BLOOD
DR LWIINDI

BLOOD
? Composition And Functions
? Blood is a fluid, which circulates in the
vascular channels of human body due to the
pumping action of heart.
? It is red in color and consists of a liquid
portion called plasma in which various types
of cells are present.
? The cells which are suspended in the plasma
are of three different types

? 1.Erythrocytes or red blood cells
? The color of these cells is red due to presence
of an iron containing pigment known as
hemoglobin.
? 2.Leucocytes or white blood cells
? They are of different types (5)
? 3.Thrombocytes or Plateletes
? These cells help in the coagulation of blood

GENERAL FUNCTIONS OF BLOOD
? Blood performs various important functions,
which could be summarized as follows;
? 1.Respiratory Tissues and organs require a
constant supply of oxygen to maintain their
activity and simultaneously they form carbon
dioxide and other waste products.
? Blood and particularly the red blood cells are
responsible for transport of oxygen from the
lungs to the tissues.
? This is due to the presence of hemoglobin, which
combines with oxygen to form oxy-hemoglobin.
Carbon dioxide from tissues is taken up by the
blood and released in the lungs.

? 2.EXCRETORY
? As a result of metabolic activity there is a
constant production of waste products.
? Blood transports them to the kidneys, lungs,
skin and gastrointestinal tract for excretion.
? 3. NUTRITIVE
? Food is digested into simpler end products in
the digestive tract.
? These substances are absorbed from the
intestine and transported to all parts of the
body by the blood

? 4.DEFENSIVE
? Blood protects the body against infections.
This is achieved in different ways.
? Leucocytes have the ability to engulf and
destroy invading organisms and the property
of white blood cells is termed as phagocytosis.
? These cells form the defense force of the body
and during infection their count increases.
? This virtue forms the basis of immunization
against diseases.

? 5.COAGULATION
? It is a mechanism by which various factors
present in the blood form a clot and thus
prevent blood loss
? 6.ACID BASE EQUILIBRIUM
? Cell and enzyme activity require maintenance
of a constant acid base equilibrium.
? Blood contains buffers which maintain the pH
constant.

? 7.BODY TEMPERATURE
? The water content of the blood is 90%. It has a high
specific heat and high latent heat of evaporation,
which help blood to maintain the body temperature.
? 8.TRANSPORT OF SUBSTANCES
? Blood is in rapid circulation and as such substances like
hormones, vitamins and drugs are easily transported
all over the body.
? 9. PROTEIN RESERVE
? Plasma proteins to a certain extent act as protein
reserve and are used in extreme protein deficiency to
form cell proteins.

Water: 93-95%
Plasma: 50-60%
Solutes: 5-7% Proteins:
Nutrients
Products
Electrolytes:
Others: urea, gases.
WBC, Platelet: 1%
RBC: 40-50% (male)
37-48% (female)
Section 1 Components and Characteristic
Whole
blood

Blood Components
? Water:
�C 93~95% (plasma); 65~68% (RBC); 81~86% (whole blood).
�C Solvent, humoral balance, osmotic pressure.
? Electrolytes:
�C Na+, K+, Mg2+, Cl-, HCO3-, etc. Cell shape, pH.
? Proteins:
�C Albumin: 40-48g/L. Colloidal osmotic pressure; carrier;
buffer pH.
�C Globulin: 15-30g/L. Immune reaction: antibody; carrier.
�C Fibrinogen: 2-4g/L. Blood coagulation.

�C Hemoglobin (Hb):
? 120-160g/L (male), 110-150g/L (female)
? Function: carry gases.
? Others:
�C carbohydrates, lipids, amino acid, pigments,
hormones, gas (O2, CO2), and others like urea, uric
acid.

Physical and chemical properties
? Blood pH:
�C Normal interval: 7.35~7.45.
? Regulated by lung and kidney.
? Viscosity:
�C Friction of molecules and cells in blood.
�C Relative viscosity:
? Whole blood: 4~5 times to water (RBC).
? Plasma: 1.6~2.4 times to water (Proteins).
? Anemia or body fluid loss.

? Osmotic pressure
�C Definition:
? An ability of a liquid to attract and retain water. It
drives osmosis. 300mmol/L
�C Composition and roles:
? Crystal osmotic pressure: 298.7 mmol/L.
�C Maintain shape and size of cells.
? Colloid osmotic pressure: 1.3 mmol/L.
�C Retain blood volume
�C Decide distribution of water between blood and
interstitial fluid.

PLASMA
? It is the fluid part of the blood in which formed
elements are suspended.
? The relative quantity of plasma and cells is in
the ratio of 55:45.
? If blood mixed with an anticoagulant is taken
in graduated tube and centrifuged for about
half an hour, the cells being heavier, settle at
the bottom of the tube and constitute about
45% of the blood volume.
? This is known as packed cell volume (PCV)

? 5 liter in
adult
? 45% is
packed cells
volume
(PCV)
? 55% is
plasma
volume
Dr Sitelbanat 16

Hematocrit (packed red cell volume)
- definition: fraction of the blood composed of RBC
- functional significance
- methods of determination: centrifuging blood in a
? calibrated ��hematocrit tube��
- values ~ 35% �C 45%;
~ up to 10% in severe anemia
~ up to 65% in polycytemia
- corrected Ht = 0,96 Ht (3-4% from the measured
Ht is represented by entrapped plasma)
- venous vs. arterial hematocrit ��
- relation hematocrit �C blood viscosity��

COMPOSITION
? Plasma contains 91-92% water and 8-9% of solid
substances, which are both organic and inorganic
in nature.
? In organic constituents are less than 1% and are
mostly chlorides, carbonates and phosphates of
sodium, potassium and calcium.
? Small amounts of iron, copper and iodide are also
present.
? Sodium bicarbonate present in the plasma helps
in the maintenance of blood pH during carbon
dioxide transport.

? Organic substances form the major bulk of
solids present in plasma and they are;
? Plasma proteins (6.5-8 gms %)
? Glucose (80-120mg%)
? Cholesterol and lipids (150-250mg%)
? Non-protein nitrogenous substances like urea,
uric acid, creatine and creatinine
? Hormones, enzymes and blood pigments.

? PLASMA PROTEINS
? They are specific proteins present in plasma
and are of three different types;
? 1. Albumin
? It forms the major bulk of plasma proteins and
has a molecular weight of 60,000.
? Albumin content of plasma is 4-4.5gm%.

2.Globulin
? It constitutes about 2.5 gm of plasma proteins and
has a relatively higher molecular weight of
1,30,000.
? Various types of globulins have been identified like
alpha, beta and gamma globulin.
? The latter plays an important role in antibody
formation.
? Prothrombin which helps in the coagulation is beta
globulin and its plasma content is 0.1 gm%

? 3.Fibrinogen
? Blood coagulation requires this protein.
? The chemical nature of clot is fibrin, which is formed
from fibrinogen.
? About 0.25 gm% of fibrinogen is present in blood.
? Fibrinogen and prothrombin are utilized in the clotting
and plasma devoid of these two proteins is called
serum.
? It only contains albumin and globulin.
? There are various methods by which plasma proteins
can be isolated, like half or full saturation with
ammonium sulphate or electrophoresis.

? FUNCTIONS
? 1. Colloidal osmotic pressure
? It is 25mmHg. Albumin being the major plasma
protein primarily influences the colloidal osmotic
pressure. This is responsible for preventing fluid
exit from the capillaries.
? 2. Antibody formation.
? Antibodies form an essential defense mechanism.
This virtue is attributed to the gamma globulin

? 3. Coagulation
? Fibrinogen and prothrombin are involved in the
clotting of blood. Various other clotting factors
also belong to globulin.
? 4. Transport media
? Certain substances bind themselves with
albumin, alpha and beta globulins and are
transported. The transport of hormones, metals,
drugs, dyes are examples of this function.

? 5. Erythrocyte sedimentation rate( ESR) is influenced
by the fibrinogen content of plasma.
? 6. Viscosity
? Fibrinogen and globulins, due to their high molecular
weight and irregular shape contribute to blood
viscosity.
? 7. Buffer mechanism, plasma proteins act as buffers
and maintain acid base balance.
? 8. Protein reserve.
? During emergency, cells of the reticuloendothelial
system break them into amino acid. Subsequently
these are used for the synthesis of cell protein

The erythrocyte sedimentation rate (ESR)
? - commonly used, inexpensive, but non-
specific laboratory test (Westergren, 1921)
? - measures the speed of sedimentation of
RBC/RBC aggregates in plasma over a period
of 1 hour in a vertical column of
anticoagulated blood under the influence of
gravity
? - sialic acid-rich glycoproteins on cell surface
membranes contribute to creating a negative
charge on the cells�� surface ? cellular repel ��

? - a raised ESR is associated with marked
rouleaux formation of RBCs
? - mainly depends on plasma concentration of
large proteins (fibrinogen, Ig)
? - ESR raised in systemic inflammatory &
neoplastic diseases; useful in chronic diseases,
for monitoring disease activity/response to
therapy
Erythrocyte sedimentation rate (ESR) cont��..

The basic factors influencing the ESR
- increased ESR
? with elevated fibrinogen (e.g., pregnancy, collagen vascular
diseases, malignancy).
? decreased albumin conc.
? anemia (hematocrit is reduced, red blood cell aggregates
fall faster);
? macrocytic red cells also settle more rapidly.
a decreased ESR is associated with:
? hypofibrinogenemia, hypergammaglobulinemia associated
with dysproteinemia, and hyperviscosity
? blood diseases in which RBC have an irregular or smaller
shape that causes slower settling;
? increased albumin concentration
? �C an abnormal value remains a nonspecific finding

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