Blood Lab Review: Formed Elements, Hematology, and Blood Typing

Identification of Formed Elements

Erythrocyte (RBC)
- Biconcave, anucleate in circulating blood, most numerous formed element.
- Primary function: transport of gases via hemoglobin (O2 delivery to tissues; CO2 removal to lungs).
- Life span: ~120 days in circulation.
Leukocytes (WBCs) — five types
- Neutrophil
- Granulocyte with multi-lobed nucleus and fine granules.
- Primary function: phagocytosis of bacteria; first responders to acute infection.
- Lymphocyte
- Agranulocyte; nucleus occupies most of cell; types include T cells, B cells, and NK cells.
- Primary role: adaptive immune response (antibody production, cell-mediated immunity).
- Monocyte
- Agranulocyte; kidney/horse-shoe shaped nucleus; differentiates into macrophages in tissues.
- Primary role: phagocytosis and antigen presentation.
- Eosinophil
- Granulocyte with bilobed nucleus and red/orange granules; involved in parasitic infections and allergic responses.
- Basophil
- Granulocyte with bilobed or irregular nucleus and dark granules; releases histamine and heparin during inflammation.
Platelets
- Cytoplasmic fragments from megakaryocytes; essential for hemostasis.
- Form platelet plugs and release factors that promote coagulation.
Plasma
- Liquid component of blood; contains water, electrolytes, nutrients, gases, wastes, hormones, and plasma proteins (albumin, globulins, fibrinogen).
Model relevance
- On the model, you should be able to identify each formed element by morphology and relative abundance.
- Functions overview provided below for quick recall.

Exercise 20.3: Determination of Leukocyte Counts

What you need to know
- Procedure
- Manual count vs. automated hematology analyzer.
- Manual method (classic teaching): isolate leukocytes, dilute blood if appropriate, load into counting chamber (hemocytometer), and count cells in specified grid areas to estimate WBC count; differential may require a blood smear and differential count.
- Why it is done
- To assess immune status and identify abnormalities in WBC populations that indicate infection, inflammation, leukemia, or marrow disorders.
- WBC normal percentages (typical differential)
- Neutrophils: ext{ Neutrophils}
 ightarrow ext{about } 40 ext{-}70 ext{ ext%}
- Lymphocytes: ext{ Lymphocytes}
 ightarrow ext{about } 20 ext{-}40 ext{ ext%}
- Monocytes: $ext{ Monocytes} ightarrow ext{about } 2 ext{-}8 ext{\%}$
- Eosinophils: $ext{ Eosinophils} ightarrow ext{about } 1 ext{-}4 ext{\%}$
- Basophils: $ext{ Basophils} ightarrow ext{about } 0.5 ext{-}1 ext{\%}$
- Note: percentages should sum to 100 ext{\%}.
- Interpretation: what increases/decreases in each WBC mean
- Neutrophilia (high neutrophils): acute bacterial infection, inflammation, stress, corticosteroid use.
- Neutropenia (low neutrophils): bone marrow suppression, severe infection, drug toxicity.
- Lymphocytosis: viral infections, certain bacterial infections, chronic infections.
- Lymphocytopenia: immunodeficiency, severe stress, steroids, HIV.
- Monocytosis: chronic infections (e.g., tuberculosis), autoimmune disorders, recovery from acute infection.
- Monocytopenia: rarely clinically significant; may indicate bone marrow suppression.
- Eosinophilia: parasitic infections, allergic reactions, some autoimmune diseases.
- Eosinopenia: often not clinically specific; may be seen with acute stress.
- Basophilia: myeloproliferative disorders, hypersensitivity reactions; less common.
Granulocytes vs. agranulocytes
- Granulocytes: neutrophils, eosinophils, basophils; contain cytoplasmic granules and typically have lobed nuclei.
- Agranulocytes: lymphocytes, monocytes; lack visible granules (monocytes have a kidney-shaped nucleus that may appear agranular in some stains).
Connections to foundational principles
- WBC differential reflects immune system state and hematopoietic balance.
- Differential correlates with clinical signs (fever, infection markers, inflammatory responses).

Exercise 20.4: Determination of Hematocrit

What you need to know
- How to read/determine hematocrit and plasma levels
- Hematocrit (Hct) is the percentage of blood volume occupied by packed red blood cells after centrifugation.
- Plasma percentage is the remainder: Plasma ext{-} ext{%} = 100\% - Hct\%.
- Normal hematocrit for males and females
- Typical ranges (reference values; verify with course materials):
  - Male: $Hct_{male} \approx 40\%\text{-}54\%$
  - Female: $Hct_{female} \approx 36\%\text{-}46\%$
- Equipment used
- Capillary tubes (microhematocrit tubes)
- Centrifuge for separating plasma, buffy coat, and RBC layer
- Hematocrit reader or ruler for reading %
- Define anemia and polycythemia
- Anemia: abnormally low hematocrit (reduced RBC mass/volume).
- Polycythemia: abnormally high hematocrit (increased RBC mass/volume).
Key equations and concepts
- Hematocrit percent: $Hct\% = \left( \frac{Height{RBC\ stack}}{Height{Total\ column}} \right) \times 100$
- Plasma percentage: $Plasma\% = 100\% - Hct\%$
Connections to foundational principles
- Hct reflects oxygen-carrying capacity and volume status.
- Abnormal Hct values can indicate dehydration, fluid overload, or marrow pathology.

Exercise 20.5: Determination of Hemoglobin Content

What you need to know
- Procedure
- Common methods include spectrophotometric colorimetric assays or hemoglobinometry using blood samples.
- Equipment used
- Hemoglobinometer or spectrophotometer with cuvettes.
- How to read results
- Output is typically Hb concentration in $g/dL$ .
- Normal percentage / anemia percentage
- Normal Hb ranges (typical reference values; verify with course materials):
 - Male: $Hb \approx 13.8\text{-}17.2\ \text{g/dL}$
 - Female: $Hb \approx 12.1\text{-}15.1\ \text{g/dL}$
- Anemia thresholds correspond to Hb below the lower limit for sex:
 - Female threshold: typically < $12.0\ \text{g/dL}$
 - Male threshold: typically < $13.0\ \text{g/dL}$
Connections to foundational principles
- Hb concentration directly relates to oxygen-carrying capacity of blood.
- Hb levels are influenced by plasma volume, RBC mass, and iron status.

Exercise 20.7: Determination of Blood Type

What you need to know
- What is in serum
- Serum contains antibodies (anti-A, anti-B, and anti-D in some contexts) capable of agglutinating corresponding antigens on donor RBCs.
- Procedure
- ABO and Rh typing via agglutination tests using antisera:
  - If adding anti-A serum causes agglutination, A antigen is present; if anti-B causes agglutination, B antigen is present; if both, AB type; if neither, type O.
  - Rh typing via anti-D serum to detect Rh (D antigen).
- How to read ABO and Rh blood type
- ABO result determined by presence/absence of A and B antigens on RBCs.
- Rh result determined by presence (Rh+) or absence (Rh−) of D antigen.
- Which blood types can be donated/received for each
- ABO/Rh compatibility for RBC transfusion (general rules):
  - Donor to recipient (RBC):
  - O− donor can donate to all types: O−, O+, A−, A+, B−, B+, AB−, AB+.
  - O+ donor can donate to: O+, A+, B+, AB+.
  - A− donor to: A−, A+, AB−, AB+.
  - A+ donor to: A+, AB+.
  - B− donor to: B−, B+, AB−, AB+.
  - B+ donor to: B+, AB+.
  - AB− donor to: AB−, AB+.
  - AB+ donor to: AB+ only.
  - Recipient can receive from:
  - O−: O− only.
  - O+: O+, O−.
  - A−: A−, O−.
  - A+: A+, A−, O+, O−.
  - B−: B−, O−.
  - B+: B+, B−, O+, O−.
  - AB−: AB−, A−, B−, O−.
  - AB+: AB+, AB−, A+, A−, B+, B−, O+, O−.
- For plasma transfusion, the rules differ (not the focus here unless specified).
- Definition of agglutination, antigen, antibody
- Agglutination: visible clumping of cells when antibodies bind to cell surface antigens.
- Antigen: a molecule or part of a molecule that the immune system recognizes as foreign; on RBCs for ABO/Rh typing.
- Antibody (immunoglobulin): a protein that binds specifically to an antigen (e.g., anti-A, anti-B, anti-D in typing).
Connections to foundational principles
- Blood typing integrates antigen presentation on RBC surfaces with circulating antibodies to determine compatibility.
- Understanding serology is essential for safe transfusion practice and prevention of transfusion reactions.

Page 2: Identification of Formed Elements — Model

Be able to identify the formed elements on the model
- Erythrocyte
- Leukocytes: monocyte, lymphocyte, neutrophil, basophil, eosinophil
- Platelets
Functions (summary)
- Erythrocytes: transport of O2 and CO2 via hemoglobin; gas exchange efficiency depends on hemoglobin affinity and RBC surface area.
- Lymphocyte: adaptive immunity; B cells produce antibodies; T cells mediate cell-mediated responses; NK cells kill infected cells.
- Monocyte: phagocytosis; antigen presentation; differentiate into macrophages in tissues.
- Basophil: release histamine and heparin during inflammatory responses; contributes to hypersensitivity reactions.
- Eosinophil: combat multicellular parasites; modulate allergic inflammatory responses; cytotoxic granules against parasites.
- Neutrophil: first responders; rapid phagocytosis of bacteria and debris; kill microbes with reactive oxygen species.
- Platelets: central to hemostasis and clot formation; release clotting factors and support wound repair.
- Plasma: liquid matrix that carries nutrients, hormones, waste, and blood proteins; maintains blood volume and pH balance.
Connections to previous lectures
- Structure–function relationships: morphology (e.g., RBC biconcavity, nucleus-laden leukocytes) relates to function (gas transport, phagocytosis, immunity).
- Hemostasis and immunity integrate to maintain homeostasis after injury or infection.