Blood Composition and Function
• Blood is the only fluid tissue in the
• Has both cellular and liquid
• Blood cells, or formed elements, are
suspended in a nonliving fluid matrix
What is in a blood sample?
• Erythrocytes – red blood cells (about 45% of
• Buffy coat – thin, white layer present at
• Leukocytes – white blood cells that protect
body (less than 1% of blood)
• Platelets – cell fragments (less than 1% of
• Plasma – fluid portion of blood (remaining
55% of blood)
Physical Characteristics and
• Blood is sticky and has a metallic
• Blood is scarlet with large oxygen
content and dark red/violet with poor
• Blood accounts for 8% of body weight.
– Healthy males have 5-6 L
– Healthy females have 4-5 L
1. Delivering oxygen from the lungs and
nutrients from the digestive tract.
2. Transporting metabolic waste
products from cells to elimination
3. Transporting hormones from the
endocrine organs to their target
1. Maintaining appropriate body
2. Maintaining normal pH in body
3. Maintaining adequate fluid volume in
the circulatory system.
1. Preventing blood loss
2. Preventing infection
• Yellow, sticky fluid
• Made mostly from water
• Contains over 100 different dissolved
• Contains many proteins
– Albumin is the protein with greatest
• Carries certain molecules through circulation
• Blood buffer
Blood Plasma (con’t)
• Content continuously changes by
• Also distributes heat throughout the
Red Blood Cells
• Small, flattened discs with depressed
• Basically, little “bags” or hemoglobin
(Hb – the RBC protein that aids in gas
• Pick up oxygen in the capillary bed of
the lungs and releases it to tissue cells
across the capillaries throughout the
• Transport ~20% of the carbon dioxide
by tissue cells back to the lungs.
• Spectrin, RBC protein, allows the RBC
to bend and change shape to move
through blood vessels and capillaries.
• Women typically have a lower RBC
count than men.
• Thickness of the blood is affected by
the # of RBC’s. (thicker = more RBC’s)
• Hemoglobin serves as the molecule for
– 1 hemoglobin molecule can transport 4
oxygen molecules at a time.
• Blood cells are made by hematopoiesis
in the red blood marrow.
A condition in which the blood
has an abnormally low oxygen-
It is not a disease, but a
symptom of a disease.
Causes of anemia:
1. An insufficient # of RBC’s
• Hemorrhagic anemias result from rapid
blood loss. Usually treated with
• Hemolytic anemias result from RBC’s
that rupture prematurely. It is caused by
hemoglobin abnormalities, bad blood
transfusion, or infection.
• Aplastic anemia results from destruction
or inhibition of the red marrow by
bacterial toxins, drugs, or radiation.
2. Decreased hemoglobin content
• Iron-deficiency anemia is generally a secondary
result of hemorrhagic anemias, but it can be
from an inadequate intake of iron-rich foods.
• Athlete’s anemia occurs when athletes exercise
vigorously, expanding their blood volume by as
much as 15%, diluting the blood. Converts back
within a day or so.
• Pernicious anemia is caused by a deficiency of
vitamin B12, which is provided by meats,
poultry and fish.
3. Abnormal hemoglobin
• Thalassemias are typically seen in people of the
Mediterranean ancestry (Italians and Greeks).
RBC’s are thin, delicate, and deficient in
• Sickle-cell anemia is caused by an abnormal
hemoglobin molecule which causes the RBC’s
to become crescent shaped. The standard
treatment is blood transfusion. Occurs chiefly
in black people who live in the malaria belt of
Africa and among their descendants.
• Abnormal excess of erythrocytes that
increase blood thickness
• Treated by blood dilution
• “Blood Doping”
– Artificially induced polycythemia
– Practice of drawing off RBC’s and
reinserting them later.
– Used by athlete’s to increase blood’s
White Blood Cells
• Only formed element that is a true cell
• Critical to our defense system
• Protects the body from bacteria,
viruses, parasites, toxins, and tumor
• Slip in and out of capillaries through a
process called diapedesis.
– WBC’s follow a signal
– Go to the area of damage and infection to
destroy foreign substances or dead cells
• When mobilized, body speeds up WBC
production, doubling the # in the blood.
– When WBC count goes over 11,000 cells
per mL, this is called leukocytosis.
• Most numerous of the WBC’s - ~ ½ of
• Chemically attracted to inflammation
• Phagocytize bacteria and fungi
• The body’s “bacteria slayers”;
numbers increase during bacterial
• Filled with digestive enzymes
• Lead the attack against parasitic
• Found in intestinal or respiratory
• Tend to “hang out” where parasitic
worms may enter
• Rarest WBC
• Cytoplasm contains histamine-
– Histamine is an inflammatory chemical
that acts as a vasodilator and attracts
most numerous leukocyte
• Large amounts in body; however, small
amounts in blood
• Found in lymphoid tissue (lymph nodes,
• T lymphocytes (T cells) act against virus-
infected cells and tumor cells.
• B lymphocytes (B cells) make plasma cells,
producing antibodies that are released into
• Largest leukocytes
• Phagocytic and increase in numbers
• Defend against viruses and parasites
• Group of cancerous conditions involving
• Without treatment, all are fatal
• Immature WBC’s flood into bloodstream
• Bone marrow becomes totally occupied by
• Because healthy blood cells are crowded out,
anemia and bleeding disorders occur.
• Symptoms include fever, weight loss,
and bone pain.
• Most common causes of death are
internal bleeding and infections.
• Treatments include radiation and
antileukemic drugs to destroy cancer
• Bone marrow transplants are used in
• Called the “kissing disease”
• Highly contagious viral disease seen in
children and young adults
• Caused by the Epstein-Barr virus
• Symptoms include feeling tired and
achy, sore throat, and a low-grade
• No cure must run its course!!
Are not cells, only fragments,
• Essential for clotting when blood
vessels are injured
• Stick to the damaged site, forming a
temporary plug to seal break
• Quickly degenerate because they have
• Stopping of bleeding
• “Plug the Hole” defensive reaction
• Three main phases…
Phases of Hemostasis
1. Vascular Spasms
• Immediate response constrict blood vessel
• Chemicals released cause vasoconstriction
2. Platelet Plug Formation
• Temporary plug formed to seal break
• Positive feedback mechanism increases the
numbers of platelets to the site to build the plug
• Blood turns from liquid to gel
• Multistep process that requires 30 different
Anything that interferes with
the clotting mechanism can
result in abnormal bleeding.
• A condition in which the # platelets is
• Causes spontaneous bleeding from blood
vessels all over the body
• Even normal movement can cause
hemorrhages (petechiae = small purple
• Arises from any condition that suppresses or
destroys the bone marrow
• Blood transfusions give temporary relief
Impaired Liver Function
• Several different hereditary bleeding
• Sex-linked genetic disorder
• Primarily in males
• Lack clotting mechanisms in the blood
• Causes prolonged bleeding with even
• Must receive transfusion or injections
of clotting factors.
Transfusions of Whole Blood
• The human cardiovascular system is
designed to minimize the effects of
blood loss by:
1. reducing the volume of affected blood
vessels, which helps to maintain normal
2. stepping up the production of RBC’s.
• A loss of 15-30% of blood causes pallor
• More than 30% results in severe shock,
which can be fatal
• Whole blood transfusions are routine
when blood loss is substantial.
Human Blood Groups
• People have different blood types and
transfusion of incompatible blood can be
• RBC’s membranes have specific antigens on
their external surfaces.
• One person’s RBC proteins may be
recognized as foreign if transfused into
someone with a different RBC types
• The presence or absence of antigens allows
a person’s blood cells to be classified in
several blood types.
ABO Blood Groups
• ABO blood groups are based on the
presence or absence of two agglutinogens,
type A and type B
• Depending on a person’s inheritance, his or
her ABO blood group will be one of the
Blood Groups (con’t)
• The O blood group, which had neither
agglutinogens, is most common.
• AB is the least prevalent of the blood
• Presence of either the A or the B
agglutinogen results in group A or B,
Rh Blood Groups
• There are at least 8 different types of Rh
agglutinogens, called an Rh factor.
• Most people are Rh+, RBC’s carry the Rh antigen.
• If a person receives Rh+ blood, the immune system
becomes sensitized and begins producing anti-Rh
antibodies against the foreign antigen soon after the
• No problems (hemolysis) occurs the 1st
time, however, and every time thereafter will
result in attack and rupture of the donor RBC’s.
• An important problem related to the Rh factor
occurs in pregnant Rh- women who are
carrying Rh+ babies.
pregnancy will be successful, and will
result in a healthy baby.
pregnancy will result in hemolytic disease
of the newborn. The mother’s anti-Rh
antibodies built up from the 1st
attack the baby’s RBC’s.
• RhoGAM, a serum containing anti-Rh
agglutinins, is administered.