Blood
STRUCTURE AND FUNCTION
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Facts about Blood
• The only fluid tissue in
the body
• Sticky, opaque fluid
• Metallic, salty taste
• Alkaline pH between
7.35-7.45
• Temperature is 38° C
(100.4° F)
• Volume in healthy adult
male is 5-6 liters; about
8% of body weight
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2
3
4
5
Venous blood, 1 & 2, is
slightly darker due to low
oxygen content. Oxygen
gives arterial blood, 3, 4 &
5, a much brighter color.
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Functions of Blood
• Blood transports
substances
throughout the body
through blood
vessels
• Carries nutrients,
respiratory gases,
and other substances
throughout the body
• Distributes body heat
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Components of Blood
1. Solid Component or
Formed Elements
(living):
• red blood cells
• white blood cells
• platelets
2. Liquid Component
(non-living): plasma
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Erythrocytes
Thrombocytes
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Leukocytes
Hematocrit
• Blood samples
are spun in a
centrifuge
• Formed
elements settle
at the bottom &
plasma rises to
the top
The ratio of red blood
cells to total blood
volume is the hematocrit.
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Plasma
• Liquid portion of blood,
90% water
• Makes up 55% of blood
volume
• Contains over 100
dissolved substances
including nutrients,
salts (electrolytes),
respiratory gases,
hormones, plasma
proteins, and various
wastes
Albumin is the most
abundant plasma protein
found in blood. It helps
maintain osmotic pressure
of blood by keeping water
in the bloodstream.
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Formed Elements
Red blood cells are the
most numerous blood
cells; white blood cells
are the largest
• Together, make up
about 45% of blood
• Red blood cells
carry oxygen & CO2
• White blood cells
play a role in
immunity
• Platelets are
responsible for
blood clotting
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Red Blood Cells: Erythrocytes
• 44% of blood volume
• Function to carry oxygen
• Shaped like a biconcave
disk, increases surface
area
• No nucleus
• Live 100-120 days; old
cells are destroyed in
liver or spleen
• Low number or reduced
function is anemia
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Hemoglobin
• An iron-bearing
protein that carries
oxygen and gives
blood its red color
• A single RBC
contains about 250
million hemoglobin
molecules
• Each hemoglobin
molecule can carry 4
molecules of oxygen
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White Blood Cells: Leukocytes
• Defend the body against
•
•
•
•
Bacteria
Viruses
Parasites
Tumor cells
• Less than 1% of total
blood volume
• Leukocytosis is the
increase in wbc
production to fight
infection
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Types of Leukocytes
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Phagocytosis
• The process of engulfing
and destroying
microorganisms, cellular
debris, and other foreign
or toxic substances
• Leukocytes can leave the
circulatory system and
move around inside
body tissues to fight
invaders such as bacteria
• They respond to certain
chemicals released by
damaged cells
Most phagocytosis is
performed by
neutrophils
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Macrophage
• Monocytes change
into macrophages
when they enter
infected tissues
• They recognize,
engulf and destroy
target cells
• Image shows
macrophages in
infected lung tissue
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Pus
A collection of dead leukocytes
at the site of an infection.
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Platelets: Thrombocytes
• Cell fragments
• Necessary for blood
clotting process
• A blood clot on the
surface of skin
forms a scab
• Bruises are caused
by bleeding under
the skin
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HEMATOPOIESIS
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All Blood Cells Differentiate from
Stem Cells in Bone Marrow
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Hematopoiesis
• Blood cell formation
• Occurs in red bone
marrow
• All formed elements
come from a type of stem
cell called a
hemocytoblast
• Most blood cells are
formed in the red marrow
of the vertebrae and
pelvis
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Hemocytoblasts are Stem Cells
that develop into Blood Cells
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HEMOSTASIS
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Hemostasis
• Hemostasis is the
process of stopping
blood flow
• A series of reactions
triggered by a break
in a blood vessel
wall
• Response is fast and
localized
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3 Stages of Hemostasis
1. Vascular Spasms
2. Platelet Plug
Formation
3. Coagulation
Events
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Vascular Spasms
• Damaged blood vessels constrict to reduce
blood loss
• Most effective in smaller vessels
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Platelet Plug Formation
• Platelets detect damage, become sticky and
cling to the damaged area
• Anchored platelets release chemicals that
attract more platelets
• A small mass is formed called a platelet plug
platelet plug
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Coagulation
• A complex series of reactions that eventually
convert a soluble protein called fibrinogen
into an insoluble fiber called fibrin
• A fibrin mesh forms to strengthen the platelet
plug and trap red blood cells
blood clot
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Fibrin Mesh
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Scab
Scabs fall off when
the underlying skin
is fully healed.
• Protective crust
that forms over an
injury
• Once a platelet plug
is no longer
needed, it begins to
dry out and form a
scab
• The scab protects
underlying tissues
as they are
regenerated
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BLOOD GROUPS & TRANSFUSIONS
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Blood Types
• 4 inherited blood
types exist in the
human population
• Type O is most
common
• Type AB is least
common
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ABO Blood Groups
• Differences in blood
type are due to the
presence or absence
of proteins (antigens)
on the surface of red
blood cells
• Antigens will
determine the type of
antibodies produced
in the plasma
Red blood cells have either:
• A antigens
• B antigens
• Both A & B
• Neither A nor B
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Antigens & Antibodies
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Determining Blood Type
• A blood sample is
mixed with
• Anti-A
• Anti-B
• Anti-Rh
• Clumping or
agglutination
indicates the
presence of the
antigen
Anti-A
-
Anti-B Anti-Rh
+
+
Results:
• A antigen NOT
present
• B antigen present
• Rh antigen present
Conclusion: Type is B+
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Blood Transfusions
If blood of an incompatible type is introduced, the patient’s
plasma (serum) antibodies will react with red blood cell
antigens, and aggregation or clumping will occur.
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Complications of Transfusing
Incompatible Blood
• Aggregation or agglutination of blood in the
body leads to:
• Clogging of small blood vessels
• Destruction of erythrocytes
• Free hemoglobin molecules can cause fatal
kidney damage
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Rh Factor
The Rh factor was first
discovered in the
blood of Rhesus monkeys.
• Another type of protein
sometimes found on the
rbc
• Rh- people do not
automatically have
antibodies against Rh
• First exposure of Rhperson to Rh+ antigens
will cause the
production of antibodies
• Second exposure will
result in recipient’s
antibodies attacking and
rupturing donor’s Rh+
red blood cells
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Rh Factor Complications during Pregnancy
• When Rh- mother carries
her first Rh+ baby, her
body will produce
antibodies, but baby is
not affected
• The second pregnancy
will result in her
antibodies crossing the
placenta and attacking
the baby’s red blood cells
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Universal Donor & Recipient
• The absence of rbc
antigens makes those
with type O- blood able
to donate to any other
type: universal donor
• The absence of
plasma antibodies
makes those with
type AB+ blood able
to receive
transfusions from
any other type:
universal recipient
Type O-: no antigens
Type AB+: no antibodies
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DISEASES & CONDITIONS
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Anemia
• Reduced ability of
the blood to carry
oxygen
• Several different
types of anemia exist
Common symptoms of anemia:
• May result from:
• Pale or sallow skin
• Low number of rbc
• Abnormal or deficient
hemoglobin content
• General fatigue
• Weakness
• Shortness of breath
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Sickle Cell Anemia
• Inherited form of
anemia
• Hemoglobin does not
form properly giving
red blood cells a sickle
shape
• Abnormal red blood
cells rupture easily and
get clogged in small
vessels
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Hemophilia
• A sex-linked genetic
blood disorder in
which blood does
not clot properly
• May lead to
excessive internal
or external bleeding
• Can be treated with
IV clotting factors
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Leukemia
Red bone marrow becomes cancerous and
produces large numbers of abnormal white
blood cells that do not function properly.
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Undesirable Clots
• A blood clot that
forms in a blood
vessel and does not
move to another
area of the body is
called a thrombus.
• If the clot moves to
another part of the
body, it is called an
embolus.
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The End
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