Page 118 - Biology Form Two

Biology for Secondary Schools

Agglutination can be fatal. There are four major groups of blood, which are group
A, group B, group AB, and group O. Table 5.3 shows a summary of blood groups
with the antigens and antibodies present in them.

Table 5.3: Blood groups according to ABO blood grouping system
FOR ONLINE READING ONLY
Blood group Antigen on the membrane Antibody in the plasma
of the red blood cell
A A b
B B a
AB A and B None
O None a and b

Rhesus factor leaks into the mother. This causes the
This factor is named after the Rhesus mother’s body to produce antibodies
monkey in which it was first observed. which destroy some of the foetus’s
The Rhesus factor is found on the surface red blood cells. This destruction is
membrane of the red blood cells. When minimal in the first child pregnancy.
the Rhesus factor is present on the red For the children that follow, a lot of

blood cell membrane, a person is said to destruction can take place and death
be Rhesus positive. This is abbreviated of the foetus may occur. This is called
as Rh . If it is absent, the person is Rh disease or haemolytic disease of the
+
rhesus negative. This is abbreviated newborn or erythroblastosis foetalis. To
as Rh . Thus, a person’s blood is said prevent this, the mother is treated with
‾
to be A if it is blood group A and has anti-rhesus globulin. This prevents her
+
the Rhesus factor Rh , or is said to be body from forming antibodies against
+
A if it is blood group A but lacks the the rhesus antigen. However, if there
–
Rhesus factor. There are also B or B , is no leakage that causes mixing up of
+
–
O or O and AB or AB blood groups. the two blood samples, no effect will
+
+
–
–
Usually the Rh is more common in occur.
+
the population than the Rh . If a rhesus Blood transfusion
‾
negative woman marries a Rhesus
positive man, their children are highly Task 5.6
likely to be rhesus positive. During the Search the library and internet sources
last months of pregnancy, the Rhesus for information on blood transfusion.
antigen from the foetus may pass into Then, write short notes.
the mother’s blood if the foetal blood

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