Packed Cell Volume (Hematocrit) and Red Blood Cells Quiz

Red Blood Cells and Hematocrit

• Packed cell volume (hematocrit) measures the proportion of blood volume made up by red blood cells (RBCs).
• Plasma makes up approximately 55% of blood volume.
• Healthy men have an average of 5.4 million RBCs per cubic millimeter.
• Healthy women have an average of 4.8 million RBCs per cubic millimeter.
• The average lifespan of RBCs is 120 days.
• RBCs are derived from stem cells in the bone marrow.
• Growth induction and production of increased numbers of erythrocytes are caused by erythropoietin (EPO).

Measuring Packed Cell Volume

• The first step in measuring packed cell volume is to add anticoagulant to the blood sample.
• After allowing the blood to enter the capillary tube, the tube should be sealed at one end and centrifuged.

Characteristics of RBCs

• RBCs change shape to squeeze through capillaries.
• The hematocrit (packed cell volume) reflects the volume of red blood cells.

Anemia and Related Conditions

• Polycythemia is characterized by an increase in packed cell volume above the reference range.
• Microcytic hypochromic anemia can be caused by iron deficiency.
• Megaloblastic anemia is associated with vitamin B12 and folic acid deficiency.
• Primary polycythemias are caused by genetic mutations.
• Hemolytic anemia is associated with premature destruction of RBCs.
• Aplastic anemia results from a lack of functioning bone marrow.
• Anemia can cause a decrease in packed cell volume.
• Bone marrow failure can result from exposure to high-dose radiation or chemotherapy for cancer treatment.
• Anemia can also be caused by vitamin B12 and folic acid deficiency.
• Anemia is characterized by a decrease in packed cell volume below the normal range.
• Polycythemia results in an increase in hematocrit, hemoglobin, or RBCs.