How many types of blood are there in all ?
– Human blood is grouped into four types A, B, AB and O.
– Each blood type can either be Rhesus positive (Rh+) or Rhesus negative (Rh-)
– Blood contains the same basic components (red cells, white cells, platelets, and plasma.
– It was an Austrian Biologist Karl Landsteiner (1868-1943) who discovered the 4 blood groups.