The Blood
General Info
Blood is part of the circulatory system
 It is a connective tissue (relatively small
number of cells suspended in a large matrix)
 The cellular elements of blood are collectively
referred to as “formed elements”
 The matrix consists of protein and other
molecules suspended in a watery fluid called
plasma
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Microscopic View of Blood
Functions of Blood
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It maintains homeostasis in the following
ways:
– Transportation – moves nutrients from the
digestive system to body tissues as well as
oxygen from lungs, and hormones from
endocrine glands; also moves waste materials
such as carbon dioxide and nonprotein
nitrogen substances to places for disposal
Functions Continued
Protection – protects body from foreign
invaders such as microorganisms and their
toxins using phagocytic WBCs and
specialized proteins called antibodies;
protects against fluid loss by clotting
 Regulation – regulates pH with a system
of buffers; also regulates body
temperature by cooling or heating parts of
the body
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Properties of Blood
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In spite of individual differences from
person to person, the following are shared
characteristics of all blood and may be
used as an indicator of a person’s health:
– Color, volume, viscosity, and pH
Color
Blood is RED because of a protein called
hemoglobin (contains iron atoms) which
forms a chemical bond with oxygen
 Oxygenated blood (found in arteries) has
a bright red, crimson color
 Deoxygenated blood (found in veins) has
a dark-red color with a slightly bluish tinge

Arterial (Oxygenated) Blood
Venous (Deoxygenated) Blood
Volume
Represents approximately 8% of total
body mass (density is approx 1.05 g / ml)
 Average male has 5 – 6 liters, average
female has 4 – 5 liters

Viscosity
Blood is thicker, denser, and more
adhesive than water
 Blood flows about 5 times more slowly
than water
 The resistance to flow is called viscosity

pH
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Blood is slightly alkaline (or basic) with a pH
that usually ranges between 7.35 and 7.45
Maintained by a buffering system that
removes Hydrogen ions
Low pH called acidosis or acidemia and body
cells stop functioning
High pH called alkalosis or alkalemia
Both conditions represent major disruptions
to homeostasis
Plasma
Liquid portion of blood
 Yellow-ish fluid that suspends the formed
elements of blood
 Also contains gases, metabolic wastes,
nutrients and hormones
 Made up of mostly water (92%) and
primary solute is protein

Plasma Proteins
Most of these are synthesized in the liver
 More than 50 different types of protein
found can be classified into one of 3
groups: albumins, globulins, and
fibrinogen

Albumins

Albumins – compose 55% of blood’s
proteins; increase blood’s viscosity which
determines how easily blood can flow
through vessels and how easily plasma
can pass trough blood vessel walls to the
interstitial fluid
Globulins
Globulins make up 38 % of proteins found
in plasma
 There are several types of globulins but
the most important are called gamma
globulins, which function as antibodies in
the immune response
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Fibrinogen
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Remaining 7 % of blood proteins are
fibrinogen
Play a major role in blood-clotting, also
known as hemostasis
When fibrinogens and other blood-clotting
factors are selectively removed from blood,
the remaining product is called blood serum
This makes the storage and reuse of blood
much more convenient
Other Plasma Solutes
One category of these solutes and called
nonprotein nitrogenous (NPN) substances;
includes amino acids, urea, and uric acid
 Gases – Oxygen and carbon dioxide (plus a
significant amount of nitrogen, but it plays no
physiological role
 Nutrients include simple sugars, fats, and amino
acids
 Electrolytes – sodium, chloride, bicarbonate,
potassium, calcium, phosphate, sulfate, and
magnesium ions – concentrations regulated by
kidneys to control variations due to diet
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