Lab 23: White blood cell

Overview of Red Blood Cells and Anemia

  • Red Blood Cell (RBC) Flexibility

    • RBCs exhibit considerable flexibility, allowing them to change shape and navigate through narrow capillaries.

  • Anemia

    • Definition: A medical condition characterized by a reduced number of red blood cells (RBCs) or hemoglobin levels, impairing the blood's capability to carry oxygen.

    • Key Types of Anemia

    • Microcytic Hypochromic Anemia

      • Characterized by smaller than normal red blood cells and low hemoglobin concentration.

      • Commonly due to iron deficiency.

      • Prevalence: Approximately 20% of females and about 3% of males in the U.S. suffer from anemia.

    • Macrocytic Anemia

      • Characterized by larger than normal RBCs, often resulting from inadequate vitamin B12 or folate.

Hemoglobin Function and Types

  • Oxygen Binding

    • Oxygen binds to the iron in the heme group of hemoglobin.

    • Only one oxygen molecule can bind at a time to a single heme group.

  • Carbon Dioxide Transport

    • Carbon dioxide (CO2) is also carried in the blood, specifically on the amino acid part of the hemoglobin molecule, forming carbaminohemoglobin.

  • Carbon Monoxide Toxicity

    • Carbon monoxide (CO) binds to hemoglobin with a significantly higher affinity than oxygen, leading to carbon monoxide poisoning.

    • Treatment often involves placing patients in a hyperbaric chamber to increase oxygen concentration, driving off the CO.

Laboratory Measurements

  • Hematocrit and Hemoglobin Measurements

    • The hematocrit is the percentage of blood volume occupied by red blood cells. Traditionally, hematocrit was divided by three to estimate hemoglobin levels, though this method may not hold for all patients.

    • Anemia is diagnosed based on these measurements, with particular importance on mean corpuscular volume (MCV) and mean corpuscular hemoglobin concentration (MCHC).

    • Mean Corpuscular Volume (MCV)

    • Indicates the average size of RBCs.

    • Normal range: 82-92 fL.

    • Anemia can arise from either enlarged (macrocytic) or small (microcytic) RBCs.

    • Mean Corpuscular Hemoglobin Concentration (MCHC)

    • Reflects the average hemoglobin concentration in RBCs. Normal range: 32-36 g/dL.

    • Below 32 g/dL indicates hypochromic anemia (not enough hemoglobin), while above 36 g/dL indicates hyperchromic (too much hemoglobin).

Blood Types

  • ABO Blood Group System

    • Blood type determined by glycoproteins on the surface of RBCs.

    • Blood types: A, B, AB, and O are identified by the presence or absence of A/B antigens.

    • Individuals produce antibodies against blood types they do not possess. For example, type A individuals produce antibodies against type B.

  • Importance of Blood Typing

    • Blood type compatibility is crucial during blood transfusions to prevent serious immune reactions such as agglutination, which can clump blood cells together, potentially leading to death.

White Blood Cells

  • Classifications of White Blood Cells (WBCs)

    • Neutrophils (60-70% of WBCs): Multi-lobed nucleus, neutral granules.

    • Lymphocytes: Smallest WBCs with large nuclei, essential for immune response.

    • Eosinophils (2-4%): Involved in allergic reactions and parasitic infections; characterized by bi-lobed nuclei and granules.

    • Basophils: Least common WBCs, involved in allergic response. Their granules obscure the nucleus from view.

Laboratory Techniques

  • Blood Slide Preparation

    • Method of making a blood slide involves placing a small drop of blood on a microscope slide, spreading it out, letting it dry, and then staining it with fixatives. Techniques include careful handling and appropriate use of stains to visualize blood cells effectively.

  • Microscoping and Counting

    • Counting should be performed on properly prepared slides to quantify white blood cells. A common technique is to count different cell types across a definable area in a set time frame (e.g., 5 minutes).

Anemia Diagnosis and Treatment

  • Diagnosis

    • Anemia can be diagnosed through measurement of hematocrit, hemoglobin, MCV, and MCHC levels.

    • Different results classify the type of anemia, with microcytic hypochromic anemia being the most common.

  • Treatment Considerations

    • Treatment often depends on the underlying cause of anemia (e.g., iron deficiency, chronic infection, etc.) and may include supplements or medical interventions.