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results in a rough surface that is ideal for the -adhesion of
the platelets, thus starting the clotting mechanism. Too
much cholesterol in the diet from eating too much fatty
food contributes to the formation of these masses. Clotting
in such an unbroken vessel is called throm-bosis (throm-
BOH-sis) and the clot itself is called a thrombus-
(THROM-bus). A thrombus may dissolve. However, if it
remains intact, it can damage tissues be-neath it by cutting-
off oxygen supplies. If a piece of a blood clot dislodges and
gets transported by the blood-stream, it is called an
embolus (EM-boh-lus). When an embolus becomes
lodged in a vessel and cuts off circu-lation, it is called an
embolism (EM-boh-lizm). When a blood clot forms in a
vessel that supplies a vital organ, it is designated in a
special way. If the brain is affected, it is called a cerebral
thrombosis. If the heart is af-fected, it is called a coronary
thrombosis. If the tissues are killed, it is called an
infarction (in-FARK-shun) and is often fatal. If a blood
clot dislodges and travels to a vital organ like the lungs and
blocks a vessel supplying that organ, it is referred to as a
pulmonary embolism. To prevent embolisms from
occurring after surgery, patients are expected to walk or
ambulate as soon as possible so that the normal destruction
of cellular and tissue debris can occur through the activities
of the WBCs and phagocytosis.
The Blood Groups
Human blood is of different types and only certain
combinations of these blood types are compatible.
-Procedures have been developed for typing blood. This
ensures that donor and recipient blood transfusions are
compatible. If blood groups are mismatched, agglutina-
tion (ah-gloo-tih-NAY-shun) or clumping of RBCs will
occur. This is called a transfusion reaction and is caused by
a reaction between protein antibodies in the blood plasma
and RBC surface molecules called antigens. It is just a few
of the many RBC antigens that can cause a se-rious
transfusion reaction. These are the antigens of the ABO
group and the Rh group.
Agglutination of RBCs is the result of a transfusion
reaction caused by mismatched blood. The individual will
experience headache and difficulty breathing, the face will
appear flushed, and there will be accompanying pain in the
neck, chest, and lower back. The RBCs will be destroyed,
their hemoglobin converted to bilirubin, which
accumulates, causing jaundice or yellowing of the skin. The
kidneys may fail.
Chapter 13The ABO Blood Group
The ABO blood group consists of those individuals who
have the presence or absence of two major antigens on the
RBC membrane, antigen A and antigen B. Due to
inheritance, a person’s RBCs contain only one of four
antigen combinations: only A, only B, both A and B, or
neither A nor B.
Based on these facts, blood is typed. Someone with
only antigen A has type A blood. An individual with only
antigen B has type B blood. Someone with both antigen A
and antigen B has type AB blood. If, however, a per-son
has neither antigen A nor antigen B, then that indi-vidual
has type O blood. Antibodies are formed during infancy
against the ABO antigens not present in our own RBCs.
Individuals with type A blood have antibody anti-B in their
plasma; those with type B blood have antibody anti-A;
those with type AB blood have neither antibody; finally,
those with type O blood have both antibody anti-A and
antibody anti-B. An antibody of one type will react with an
antigen of the same type and cause agglutina-tion.
Therefore, a person with type A (anti-B) blood must not
receive blood of type B or AB. Likewise, a person with
type B (anti-A) must not receive type A or AB blood.
Similarly, a person with type O (anti-A and -anti-B) must
not receive type A, B, or AB blood. However, a person
with type AB blood, which lacks both anti-A and anti-B
antibodies, can receive a transfusion of blood of any type
and is therefore known as a universal recipient. A person
with type O blood lacks antigens A and B and is known as
a universal donor, because type O blood could be trans-
fused into people with any of the blood groups.The Rh Blood Group
The Rh blood group was named after the Rhesus mon-
keys, the animals in which one of the eight Rh antigens or
factors was first identified and studied. This was anti-gen D
or agglutinogen D, which was later discovered in humans.
If antigen D and other Rh antigens are found on the RBC
membrane, the blood is Rh positive. Most Americans are
Rh positive. If the RBCs lack the antigens, the blood is Rh
negative. The presence or absence of the antigens is an
inherited trait.
Unlike the antibodies of the ABO system, anti-Rh
antibodies do not develop spontaneously. -Instead, they
develop only in Rh-negative persons if an Rh--negative
person receives a blood transfusion of Rh-positive blood.
Shortly after receiving the mismatched Rh--positive blood,
the Rh-negative person begins to produce anti-Rh