BLOOD
COMPONENTS, PHYSICAL
CHARACTERISTICS, AND VOLUME
Blood transports everything (nutrients, wastes,
and body heat)
 Blood is a complex fluid connective tissue with
both solid and liquid components.
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Solid – living blood cells (formed elements)
Erythrocytes (red blood cells –RBCS)
 Leukocytes (white blood cells –WBCS)
 Platelets (function in the blood-clotting process)
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Liquid – nonliving fluid matrix (plasma)

An average blood sample (hematocrit) contains
(by volume):
55% plasma
 45% RBCs
 Less than 1% WBCs
 Less than 1% platelets

Blood color varies from scarlet (oxygen-rich) to a
dull red (oxygen-poor)
 Whole blood is slightly alkaline (pH 7.35 – 7.45)
 8% of body weight
 Total adult blood volume is about 6 quarts
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PLASMA
Straw-colored fluid
 90% water
 Helps to distribute body heat evenly throughout
the body
 Over 100 different solutes

(plasma proteins, nutrients, respiratory gases,
hormones, wastes, and products of cell metabolism)

Plasma proteins are most abundant solutes
Most are made by the liver
 Not used for cellular metabolism
 Composition varies continuously as cells remove or
add substances to the blood
 Body organs make dozens of adjustments daily to
maintain solutes at life-sustaining levels.
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FORMED ELEMENTS

Erythrocytes
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Ferries oxygen in blood to all cells
Anucleate
Contain very few organelles
Contains iron-containing hemoglobin (Hb) protein to
transport oxygen
Lack mitochondria and make ATP by anaerobic
mechanisms
Small biconcave cells that provide a large surface
area relative to volume
Outnumber WBCs by about 1000 to 1
About 5 million RBC/mm³ (as the RBC volume
increases, blood viscosity increases)
 The more Hb a RBC contains, the more oxygen it will
carry
 Average of 12-18 hemoglobin per 100 ml blood
 A single RBC contains about 250 million Hb
molecules

Each Hb can carry 4 molecules of oxygen
 So each RBC carry about 1 billion molecules of oxygen
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Leukocytes
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Far less numerous than RBCs
4,000 – 11,000 WBC/mm³
The only complete cells in blood (contain nuclei and
usual organelles)
Helps defend the body against damage by bacteria,
viruses, parasites, and tumor cells
Able to slip into and out of the blood vessels
(diapedesis) to cause inflammatory or immune
responses
Leukopenia is an abnormally low WBC count

Can locate areas of tissue damage and infection in
the body
Respond to certain chemicals that diffuse from the damaged
cells (positive chemotaxis)
 Following the diffusion gradient to pinpoint areas of tissue
damage
 Gather in large numbers to destroy foreign substances or
dead cells
 The body speeds up their production

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Total WBC count above 11,000 cells/mm³is referred
to as leukocytosis

Indicates the presence of a bacterial or viral infection in the
body

Platelets
Not cells in the strict sense
 Fragments of very large multinucleate cells called
megakaryocytes that rupture
 Normal platelet count in blood is about 300,000/mm³
 Needed for the clotting process
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Write a paragraph/overview of what we learned
about blood.
Draw a picture and thoroughly describe each of
the solid/cellular components of blood (RBC,
WBC and platelets)
THIS IS DUE AT THE END OF THE PERIOD!!!
BLOOD CELL FORMATION
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Occurs is red bone marrow
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Flat bones of the skull and pelvis, ribs, sternum, and
proximal epiphysis of the humerus and femur.
Each type of blood cell is produced in different
numbers in response to body needs and stimuli
 All formed elements arise from a common type of
stem cell ( hemocytoblast) in the red bone
marrow

Two types of descendents
1.
Lymphoid stem cell – produces lymphocytes
2.
Myeloid stem cell – produces all other classes of
formed elements

RBCs are unable to divide (anucleate) and have a
limited life span of 100 to 120 days
 They begin to fragment and their remains are
eliminated by the phagocytes in the spleen and
liver
 Lost cells are replaced more or less continuously
 Developing RBCs divide many times and then
begin synthesizing huge amounts of hemoglobin
 When hemoglobin has been accumulated, nucleus
and most organelles are ejected and the cell
collapses
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The young RBC (reticulocyte) still contains some
rough ER but begins transporting oxygen
 Within two days they have ejected the remaining
ER and have become fully functional erythrocytes
 The process from hemocytoblast to mature RBC
takes 3 to 5 days
 Platelet production is accelerated by
thrombopoietin
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Rate of erythrocyte production is controlled by a
hormone called erythropoietin from liver and
kidneys
When blood levels of oxygen begin to decline, the
kidneys increase release of erythropoietin
 Bone marrow is targeted and is stimulated to make
more RBCs
 Excessive amount of oxygen in the bloodstream
depresses erythropoietin release and RBC production
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Colony stimulating factors (a hormone) trigger
formation of leukocytes and platelets and also
enhance the ability of mature leukocytes to
protect the body
HEMOSTASIS
Stoppage of blood flow is fast and localized
 Blood loss at the site is permanently prevented
when fibrous tissue grows into the clot and seals
the hole in the blood vessel.
 Three phases occur in rapid sequence
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1.
Platelet plug formation
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Membrane is broken so endothelium and collagen
fibers are exposed to oxygen
Platelets become “sticky” and cling to the damaged
site
Platelets release chemicals that attract more
platelets
Platelet plug is formed
2.
Vascular spasms
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Platelets release serotonin that causes the blood
vessel to go into spasms
Blood loss decreases until clotting can occur
3.
Coagulation
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Injured tissues release thromboplastin (helps the
clotting process)
A platelet phospholipid interacts with
thromboplastin and Ca⁺ to form a prothrombin
activator
The activator converts prothrombin in the plasma
into the enzyme thrombin
Thrombin joins soluble fibrinogen proteins into
long hair-like molecules of insoluble webbing

Coagulation continued
Forms a meshwork that traps the RBCs and forms
the basis of the clot
 Within the hour, the clot begins to retract, squeezing
serum (plasma minus the clotting proteins) from the
mass and pulling the ruptured edges of the blood
vessel closer together

Normally, blood clots within 3 to 6 minutes
 Once the clotting cascade has started, triggering
factors are rapidly inactivated to prevent
widespread clotting
 Eventually the endothelium regenerates and the
clot is broken down
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Create a comic strip of hemostasis including
pictures and thoroughly descriptive captions.
DISORDERS OF HEMOSTASIS

Undesirable Clotting
Usually occurs in the legs
 Clot that develops and persists in an unbroken blood
vessel is a thrombosis
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May prevent blood flow if large enough
A thrombosis that breaks away from the vessel wall
and floats freely in the bloodstream is an embolus
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Usually no problem unless/until it lodges in a blood vessel
Caused by anything that roughens the blood vessel
endothelium and encourages clinging of platelets
 Slowly flowing blood or blood pooling is another risk
factor (especially in immobilized patients)
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Bleeding disorders
Common causes are platelet deficiency, deficits of
clotting factors and genetic conditions
 Thrombocytopenia results from an insufficient
number of circulating platelets
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Normal movement causes spontaneous bleeding from small
blood vessels (petechia)
Hemophilia is a hereditary bleeding disorder
Lack of the factors needed for clotting
 Minor tissue trauma results in prolonged bleeding and can
be life-threatening
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HUMAN BLOOD GROUPS
Plasma membranes of RBCs have genetically
determined proteins (antigens)
 Each of us tolerates our own cellular (self)
antigens
 RBC proteins will be recognized as foreign if
transfused into another person with different
RBC antigens
 Antibodies present in the plasma attach to
“foreign” RBCs causing RBCs to clump
(agglutination)
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This leads to the clogging of small blood vessels
throughout the body
 Foreign RBCs are lysed and Hb is unable to
deliver oxygen
 Clogged vessels affect kidney tubules to cause
kidney failure, fever, chills, nausea, and vomiting
may occur.
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Over 30 common RBC antigens
 ABO blood groups are based on which of the two
antigens (type A or B) a person inherits
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Absence of both antigens results in blood type O
 Presence of both antigens results in blood type AB
 Possession of either A or B antigen yields type A or B
blood, respectively
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Rh blood groups are based on agglutinogen D
(originally identified in Rhesus monkeys)
 Most Americans are Rh⁺ (RBCs carry the Rh
antigen)
 If an Rh⁺ person receives Rh⁺ blood their immune
system begins producing anti- Rh⁺ antibodies
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Hemolysis does not occur with the first transfusion
 It takes time for the body to react and start making
antibodies

In subsequent transfusions, a typical reaction
occurs (patient’s antibodies attack/rupture donor
RBCs)
 First time pregnant Rh⁺ women who carry Rh⁺
babies usually results in the delivery of a healthy
baby

Mother is sensitized by Rh⁺ antigens and forms antiRh⁺ antibodies
 If she becomes pregnant again with an Rh⁺ baby, her
antibodies will cross the placenta and destroy the
baby’s RBCs
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DEVELOPMENTAL ASPECTS OF BLOOD
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Embryonic development of the entire circulatory
system occurs within 28 days
Embryonic blood cells are circulating in the newly
formed blood vessels around day 28
Fetal Hb has a greater ability to pick up oxygen (fetal
blood is less oxygen-rich than that of the mother)
Fetal blood cells are gradually replaced by RBCs that
contain the more typical Hb
Fetal RBCs are destroyed and the products are
released in the bile
If this happens at a rate faster that the immature
liver can handle, the infant becomes jaundiced

Write a journal entry as if you are a person
suffering from a hemostatic disorder. You must
explain your disorder and how you feel about
having that disorder. You may also portray a
doctor explain what to expect while telling a
patient that they have that disorder, are
pregnant with a child who has the disorder. This
is due at the end of the period!