Haemopathy is the study of blood. The word haemopathy comes from two words, "Haema-" which refers to blood and "Patho-" which refers to a study or practice. The word Pathology, or pathology, also deals with the study of blood. This article will go into more detail about pathology later on in the text. First let's have a look at some fun facts about erythrocytes, or red blood cells: - There are approximately 5 million red blood cells per micro liter of human plasma (plasma being the liquid part) in an average adult person.