Blood Smear Microscopy, White Blood Cell microscopy and Blood smear Lab

Why should blood intended for a CBC not be clotted?

Clotting prevents accurate cell counts and evaluation.

Name two problems with blood films extending to the end of the slide.

They may be too long and uneven, making evaluation difficult.

What is the appropriate angle of the spreader slide when making a blood smear?

Approximately 30°.

Where should the blood drop be placed relative to the spreader slide?

At the end of the spreader slide

How does spreading faster affect the length of a blood film?

It creates a shorter smear.

How does spreading slower affect the length of a blood film?

It creates a longer smear.

What must be done to clearly see stained smear material at 40× with no cover slip?

Use Köhler illumination and ensure a clean objective.

Where should blood smear evaluation begin?

At the feathered edge.

What is the feathered edge of a blood smear?

The thin end where cells spread

What is the optimal zone of a blood smear?

1-2 fields from the feathered edge where RBCs are evenly spread and not overlapping.

What is the main large finding often seen in the feathered edge?

Platelet clumps, cancers (abnormal) cells, critters

What are the goals of low magnification (10×) evaluation of a smear?

Assess overall cell distribution and density.

How is a WBC differential count performed?

Count a set number of WBCs and record the % of each type.

How do nucleated RBCs affect automated WBC counts?

They are counted as WBCs, falsely increasing the count.

Why is blood smear evaluation important compared to analyzer data?

Smear provides qualitative and semiquantitative information (morphology, clumps, parasites) that analyzers may miss.

How do analyzer vs microscopic WBC concentrations differ in health vs disease?

Analyzer is more accurate in health; microscopy may be more accurate in disease.

How are concentrations of each WBC type calculated?

Analyzer total WBC × percentage from differential.

How are platelets evaluated on a smear?

At 100× oil immersion; estimate concentration, clumping, and size.

How is platelet concentration estimated from a smear?

Convert the mean platelet count per 100× oil field into estimated concentration.

What causes central pallor in discocytic RBCs?

Their biconcave shape (thin center, thicker edges).

What are the five major categories of RBC abnormalities assessed?

Shape, size, color, inclusions, arrangement

Why can WBCs not be evaluated well in old blood samples?

They deteriorate and lyse over time.

What are the typical features of segmented neutrophils?

Segmented nucleus, dense clumped chromatin, pale cytoplasm with variable pink graininess.

What are the typical features of band neutrophils?

Broader nucleus with smooth parallel sides, no focal indentations, looser chromatin.

What is the significance of reactive lymphocytes?

They indicate antigen exposure and increased protein production.

Why do reactive lymphocytes appear blue?

Increased protein synthesis stains cytoplasm darker blue.

What is the significance of lysed leukocytes?

They may reflect poor sample handling or fragile cells.

What is the function of neutrophils?

Innate immunity; phagocytosis, microbial killing (oxidative injury, enzymes, NETs), degranulation.

What is the lifespan of neutrophils in blood?

Less than 2 days.

What is the lifespan of eosinophils in blood and tissue?

What is the appearance of eosinophils?

Slightly larger than neutrophils, lobulated nucleus, prominent pink granules

What are the main functions of eosinophils?

allergy/parasite involvement.

What is the appearance of basophils?

Larger than neutrophils, ribbon-like nucleus, prominent lavender granules.

What is the function of basophils?

Parasite defense, allergy response, immunoregulation via granule content (histamine, heparin, enzymes).

What is the lifespan of basophils?

3-4 days in blood, weeks in tissue.

What is the appearance of monocytes?

Larger than neutrophils, pleomorphic nucleus, looser chromatin, blue cytoplasm.

What are the functions of monocytes?

Phagocytosis, antigen presentation, immunoregulation, tissue repair.

What do monocytes become in tissue?

Macrophages.

What are the two macrophage polarization types?

M1 (inflammatory) and M2 (healing).

What are dendritic cells?

Mobile antigen-presenting cells linking innate and adaptive immunity (not detectable in blood smears).

What removes old neutrophils from circulation?

Tissue macrophages.

What is the appearance of lymphocytes?

Variable size; small round nucleus, dense chromatin, scant cytoplasm.

What are reactive lymphocytes?

Lymphocytes with darker cytoplasm due to increased protein synthesis.

What is the lifespan of lymphocytes?

Hours to years (usually weeks to months).

What is the mononuclear phagocyte system (MPS)?

Network of monocytes, macrophages, and dendritic cells for phagocytosis and antigen presentation.

What are the steps of phagocytosis?

Attachment → engulfment → phagosome-lysosome fusion → killing.

What are the main steps of leukocyte transendothelial migration?

Rolling, firm adhesion, crawling, chemoattractant signaling, adhesion molecule involvement.

What are the leukocyte pools in blood?

Circulating pool and marginating pool.

What are the major routine leukocyte tests?

Total WBC, Manual WBC differential, and specific leukocyte concentrations.

What do gray granules in sighthound neutrophils represent, and are they pathologic?

Gray granules are a normal variant in sighthound neutrophils and should not be mistaken for toxic change.

What is the major function of B lymphocytes?

Antibody production

What types of cells can B lymphocytes differentiate into?

Plasma cells and memory cells

What are the major functions of T lymphocytes?

Cytotoxic killing, cytokine release, and memory cell formation

What are the major functions of natural killer (NK) cells?

Innate recognition and killing, cytokine release