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chapter 11: cardiovascular system : blood 11-4 (blood groups/ transfusions)
chapter 11: cardiovascular system : blood 11-4
blood groups/ transfusions
significance
there are antigens present on the cell membrane surface of our erythrocytes
our plasma contains substances called antibodies that are produced against non-self antigens
if the RBC's antigen and plasma antibody are the same, the serious condition of hemolysis of rbc's will occur
ABO blood types
inherited trait
determined by the antigens on a person's RBC
4 types: A,B,AB,O
Rh factor
inherited trait
studied on rhesus monkeys (thus, Rh)
group of antigens present on rbc's = Rh positve; lack of antigens on rbc's = Rh negative
Rh antibodies do not form spontaneously, but will form in Rh- negative persons in response to stimulation:
initial exposure does not produce harmful effects, however the Rh- negative person has now been sensitized
additional exposure causes serious hemolysis to occur
erythroblastosis fetalis = hemolytic disease of the newborn
scheme
Rh-negative mother becomes pregnant with Rh-positive fetus
the pregnancy is uneventful, but during birth, baby's blood enters the mothers circulation and causes her to produce anit-Rh antibodies
mother conceives a second Rh-positive fetus
mother's anti-Rh antibodies can now pass through the placenta and enter the fetus' circulation
the fetus' rbc's hemolyze resulting in this fatal condition
usually, no longer a significant problem because of the administration of a drug called RhoGAM, which destroys the mother's anti-Rh antibodies before they can cross the placenta and destroy the fetus' rbc's . given during week 28 of pregnancy