Final answer:
The percentage of total volume used to determine the number of erythrocytes in a blood sample is referred to as the hematocrit, which typically measures about 45 percent of erythrocytes in a normal blood sample.
Step-by-step explanation:
The percentage of total volume used to determine the number of erythrocytes in a blood sample is referred to as the hematocrit. The hematocrit measures the volume percentage of red blood cells (RBCs), or erythrocytes, in a sample of centrifuged blood. In a typical blood sample, the hematocrit is about 45 percent erythrocytes for normal blood, but this can vary from approximately 36-50 percent depending on gender and other factors. Normal hematocrit values for females range from 37 to 47, with a mean value of 41; for males, the range is 42 to 52, with a mean of 47. The process for determining the hematocrit involves spinning the blood in a centrifuge, causing the erythrocytes to settle at the bottom of a tube. The layer above the erythrocytes, the buffy coat, contains other formed elements such as leukocytes and platelets but is generally less than 1 percent of the blood sample.