Sheryl Shook
Blood Lab
Learning Objectives
- Explain hematocrit, including the significance of values outside of the normal range.
- Determine hematocrit from a blood sample image.
- Explain the ABO and Rh blood groups and their clinical significance.
- Conduct blood typing on a synthetic-blood sample.
- Identify and describe all formed elements in a human blood smear.
- State the relative proportions of formed elements in human blood.
- Demonstrate proficient microscope use.
Blood Composition and Hematocrit
Composition of blood
Overview of Blood [link opens in new window]
- 55% = Plasma
- Proteins (for blood pressure, clotting, and immune functions)
- Water (92% of plasma)
- Electrolytes
- Hormones
- Nutrients
- Blood gases
- Waste
- 45% = Formed Elements
- Red Blood Cells (erythrocytes)
- Platelets (thrombocytes)
- White Blood Cells (leukocytes)
Hematocrit
- Definition: The volume—reported as a percentage—of packed elements (mainly red blood cells) in a blood sample.
- Clinical relevance: Provides information about the oxygen-carrying capacity of blood. Low hematocrit means less red blood cells carrying O2.
- Healthy ranges:
- Male: ____________%
- Female:____________%
Blood Typing
Blood type refers to the presence or absence of specific molecules, called antigens, on the red blood cell (RBC) RBC surface. Antigens are molecules, such as proteins, lipids, carbohydrates or nucleic acids, that your body can use to differentiate self and non-self. People with different blood types have different antigens on their RBCs.
Antibodies are produced in response to some antigens (non-self), and are generally used by the immune system to recognize and facilitate removal of objects (viruses, bacteria, tumorous cells, etc.) that do not belong in the body.
There are more than 50 blood types in the human population. The most clinically significant are the ABO and Rh(+/-) blood groups.
The ABO Blood Group
A and B antigens are glycoproteins on the RCC surface. ABO typing does not affect a person’s Rh (+ or -) designation. Figure 2.3 Blood Type
Type A blood: A antigens on cell; anti-B antibodies in plasma
Type B blood: B antigens on cell; anti-A antibodies in plasma
Type AB blood: both A and B antigens on cell; neither anti-A nor anti-B antibodies in plasma
Type O blood: neither A nor B antigens on cell; both anti-A and anti-B antibodies in plasma
If a different type of blood is put into your bloodstream, the blood will agglutinate (clump) and hemolysis (bursting) occurs within the foreign blood cells. Agglutination due to antibodies and antigens is a different process than blood clotting, which involves fibrin and other cascades associated with hemostasis.
Rh Blood Group
Rh antigens are named after the rhesus macaque, a primate with many blood similarities to human. There are many Rh antigens in humans, but the D type of Rh antigen is the most clinically significant. Because of this, in blood typing, sometimes D and Rh are used interchangeably. The Rh factor is g