The Blood and Blood Vessels
Dr.Mohammed Sharique Ahmed Quadri
Assistant prof. Physiology
Al Maarefa College
Objectives
By the end of this lecture you should be able to
• Describe the composition of Blood
• Describe composition of Plasma and Types of Cells
Present [RBC, WBC, Platelets]
• List the normal Values for Hb, RBC, WBC, PLT
• Define Anemia, Polycythemia, Leukocytosis, Leukopenia,
Thrombocytosis, Thrombocytopenia
• List the different types of the blood Vessels(Arteries
,Arterioles – resistance, Capillaries, Veins)
• Define blood Pressure, Hyper tension, Hypo tension
• Define normal Heart rate
BLOOD
• Blood transports O2, nutrients to tissues and
CO2 to lungs and other products of
metabolism to kidneys.
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Blood
• Represents about 8% of total body weight
• Average volume
• 5 liters in women
• 5.5 liters in men
BLOOD COMPOSITION
• Blood consists of
– Liquid PLASMA , in which cellular elements
are present.
– Cellular Elements are
• Red Blood Cells(RBC) or Erythrocytes
• White Blood Cells (WBC) or Leukocytes
• Platelets or Thrombocyte
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Normal values
• Plasma: fluid part, 55% of total blood volume.
• Cellular elements: 45% of total blood volume.
– Red Blood Cell [RBC] – 5 millions / mm3
– Hemoglobin [Hb] – 15 gm / dl
– White Blood Cell [WBC] – 4000-11000/mm3
– Platelet – 150,000-400,000 /mm3
Blood Composition
Hematocrit or packed cell volume:
% of total blood volume occupied by RBCs.
Blood
• Consists of 3 types of specialized cellular elements
suspended in plasma (liquid portion of blood)
– Erythrocytes
• Red blood cells ( contains hemoglobin)
• Important in O2 transport
– Leukocytes
• White blood cells
• Immune system’s mobile defense units
– Platelets
• Cell fragments
• Important in hemostasis(they prevent blood
loose from damaged blood vessels).
DIFFERENT TYPES OF WBC &
THEIR FUNCTIONS
WBC
FUNCTION
1. Neutrophil (60-70%)
Phagocytosis (engulf bacteria)
2. Eosinophil (1-4%)
Important in allergic reactions
3. Basophil (0.5-1%)
Important in allergic reactions and
have heparin
4. Lymphocytes (25-33%)
For immunity
5. Monocyte (2-8%)
Tissue macrophage
PLASMA
• Plasma is transport medium for inorganic and organic
substances.
• Plasma Composition:
 Water – 90%
 Solids – 10 %
 Electrolytes [1%]– mainly Na+, Cl-, K+, HCO3-, Ca2+
 Plasma protein [6-8%]
 Organic Substances - Glucose, Amino acids, Lipids,
Vitamins
 Waste products – urea, creatinine
 Dissolved gases – O2 and CO2
 Hormones
Plasma
• Plasma proteins
– Compose 6% to 8% of plasma’s total weight
– 3 groups of plasma proteins
• Albumins
– Most abundant plasma proteins
• Globulins
– 3 subclasses
» Alpha (α)
» Beta (β)
» Gamma (γ)
• Fibrinogen
– Key factor in blood clotting

Most of the plasma protein are synthesized in liver.
Plasma
Constituent
Functions
Water (makes up
90% of plasma)
Transport medium, carries heat
Electrolytes
Membrane excitability; osmotic distribution of fluid between
ECF and ICF; buffer pH changes
Nutrients, wastes,
gases, hormones
Transported in blood; blood gas CO2 plays role in acidbase balance
Plasma proteins
In general, exert an osmotic effect important in distribution
of ECF between vascular and interstitial compartments;
buffer pH changes
Albumins
Transport many substances; contribute most to colloid
osmotic pressure
Alpha and beta
globulins
Transport many water-insoluble substances; clotting
factors; inactive precursor molecules
Gamma globulins
Antibodies
Fibrinogen
Inactive precursor for the fibrin meshwork of a clot
CLINICAL APPLICATION
• Anemia – Decrease in RBC & Hb
• Polycythemia – Increase in RBC & Hb
• Leukocytosis – Increase in WBC count (more than
11,000 /mm3
• Leukopenia – Decrease in WBC count (less than 4000
/mm3)
• Thrombocytosis – Increase in platelet count
• Thrombocytopenia – Decrease in platelet count
BLOOD VESSELS
BLOOD VESSELS
• Blood is transported to all parts of the body through
blood vessels to supply O2, nutrition and remove
the waste products e.g. CO2, Urea.
• Oxygenated blood is pumped by left ventricle to
Aorta and goes to blood vessels to supply oxygen
and nutrition to body.
• Blood is returned to right side of the heart as
Deoxygenated blood through veins.
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Basic Organization of
the Cardiovascular
System
Vascular Tree
• Consists of
– Arteries
• Carry blood away from heart to tissues
– Arterioles
• Smaller branches of arteries
– Capillaries
• Smaller branches of arterioles
• Smallest of vessels across which all exchanges are
made with surrounding cells
– Venules
• Formed when capillaries rejoin
• Return blood to heart
– Veins
• Formed when venules merge
• Return blood to heart
Arteries
• Specialized to
– Take blood from heart to the organs
– Has large radius
– Large Act as PRESSURE RESERVOIR to provide
driving force for blood when heart is relaxing
– Has thick, highly elastic wall.
– Has elastic fibers in the wall.
Arteries as a Pressure Reservoir
Arterioles
• Arterioles are highly muscular (smooth muscle).
• Have small radius
• Have no elastic fiber.
• Are Major resistance vessels
Arterioles
• Mechanisms involved in adjusting arteriolar
resistance
– Vasoconstriction
• Refers to narrowing of a vessel
– Vasodilation
• Refers to enlargement in circumference and radius of
vessel
• Results from relaxation of smooth muscle layer
Arteriolar Vasoconstriction and Vasodilation
Capillaries
• Thin-walled, small-radius, extensively branched
• have endothelial lining only between blood and
tissues.
• Sites of exchange between blood and surrounding
tissue cells (exchange vessels)
• Bring blood within reach of every cell.
• 10 billions in number.
Capillaries
Veins
– Bring blood to heart.
– Veins are thin walled as compared to arteries
– Large radius
– Also serve as blood reservoir
– serve as a BLOOD RESERVOIR (under resting
conditions nearly 65% of blood in located in the
veins).
– As they can store blood, they are called they are
called ‘CAPACITANCE VESSELS’.
Lymphatic System
• Extensive network of one-way vessels
• Provides accessory route by which fluid can be
returned from interstitial to the blood
Percentage of blood volume in different parts
of circulatory system
‘USEFUL INFORMATION’
• Normal Pulse Rate – 72 beats/min
(range 60-100 beats/min)
• Normal Blood Pressure (BP) – 120/80 mmHg
(range for systolic BP – 100-140 mmHg)
(range for diastolic BP – 60-90 mmHg)
• Hypertension (high blood pressure) – when BP is
above 140/90 mmHg.
• Hypotension (low blood pressure) – when BP is
below 100/60 mmHg.
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References
• Human physiology by Lauralee Sherwood,
seventh edition
• Text book physiology by Guyton &Hall,11th
edition
• Text book of physiology by Linda .s
contanzo,third edition
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