▶ For more Information @ http://amrita.vlab.co.in/index.php?sub=3&brch=69&sim=192&cnt=1 ▶ Amrita Virtual Lab Project website http://amrita.vlab.co.in ▶ Learn more about Amrita University http://www.amrita.edu ▶ Subscribe @ http://www.youtube.com/amritavlab https://www.facebook.com/SakshatAmrita Copyright © 2013 Under the NME ICT initiative of MHRD An adult human has about 4--6 litres of blood circulating in the body. Blood consists of several types of cells including White Blood Corpuscles or WBC and Red Blood Corpuscles or RBC floating around in fluid called plasma. There are certain protein molecules called antigens located on the surface of the red blood cells and antibodies which are in the blood plasma. The differences in human blood are due to the presence or absence of these antigens and antibodies. Individuals have different types and combinations of these molecules. According to the ABO blood grouping system discovered by Karl Landsteiner, there are four types of blood groups.