L15 - Introduction to Hematology

What is Hematology?

The study of the structure and function of blood, blood-forming organs, and their diseases

What are the 2 major components of blood?

1. Aqueous fraction → plasma

2. Cellular fraction → RBCs + leukocytes + platelets

What are the Major Constituents of Plasma?

1. Proteins → albumin, globulins

2. Electrolytes

3. Nutrients

4. Metabolic by-products

5. Signaling molecules

What important Proteins are found in Plasma?

1. Albumin

2. Globulins, including:

   • Immunoglobulins

   • Acute-phase proteins

   • Coagulation proteins

What types of Electrolytes are present in Plasma?

• Cations (+):

  1. Na⁺

  2. K⁺

  3. Ca²⁺

  4. Mg²

• Anions (−):

  1. Cl⁻

  2. HCO₃⁻

  3. Phosphate

  4. Sulfate

  5. Organic acids

What Nutrients and Metabolic by-products are found in Plasma?

• Nutrients: glucose, fatty acids, triglycerides, amino acids

• By-products: urea, creatinine, bilirubin

What are the 3 Major Types of Blood Cells?

1. Erythrocytes (RBCs)

   • O₂ delivery

2. Platelets / thrombocytes

   • Blood coagulation

3. Leukocytes (WBCs)

   • Protection from harmful agents

What is the primary function of Erythrocytes (RBCs)?

Oxygen delivery

What is the primary function of Platelets/thrombocytes?

Blood coagulation

What is the primary function of Leukocytes (WBCs)?

Protection against harmful:

• Exogenous agents → infectious organisms

• Endogenous agents → cancer

Which blood cell type is the most abundant?

Erythrocytes (RBCs)

• RBCs ~10⁶/µL > platelets ~10⁵/µL > WBCs ~10³/µL

What is a key morphologic feature of mammalian erythrocytes?

Mammalian RBCs are anucleate and their appearance varies between species.

What is a major difference between mammalian vs. non-mammalian erythrocytes?

• Mammals → RBCs lack nuclei

• Non-mammals → RBCs are nucleated

Which species shown in the lecture has distinctly elliptical/oval RBCs?

Alpaca

What are the 5 major leukocyte types?

1. Neutrophils

2. Eosinophils

3. Basophils

4. Lymphocytes

5. Monocytes

Which leukocytes are classified as Granulocytes/PMNs?

1. Neutrophils

2. Eosinophils

3. Basophils

• PMNs (polymorph-nuclears)

Which leukocytes are classified as Mononuclear cells?

1. Lymphocytes

2. Monocytes

What leukocyte is found in rabbits instead of the typical neutrophil terminology?

Heterophil

What unusual blood cell is highlighted in guinea pigs?

Kurloff cell

What granulocyte is demonstrated in the hawk blood smear?

Heterophil

What are Thrombocytes in non-mammalian species?

The blood cells corresponding to the coagulation function of platelets

• Unlike mammalian platelets, the hawk smear demonstrates nucleated thrombocytes

Why must clotting usually be prevented when collecting blood for hematology?

Because most hematology analyses require the blood to remain liquid

What are 2 key components of coagulation targeted by anticoagulants?

1. Calcium ions (Ca²⁺) → cofactors for many coagulation enzymes

2. Thrombin → key protease involved in coagulation

How does EDTA prevent coagulation?

EDTA → chelates Ca²⁺ → inhibits coagulation

What tube is commonly associated with hematology/CBC testing?

Lavender/pink-top → EDTA.

Why can K₂EDTA or K₃EDTA affect potassium measurements?

They can cause a falsely increased plasma K⁺ concentration.

How does Heparin prevent coagulation?

Heparin → activates antithrombin → inhibits thrombin → prevents coagulation.

Why can heparin be useful when collecting blood from very small animals?

The sample can be used for both hematology and blood chemistry because, unlike EDTA, the plasma can still be analyzed biochemically after hematologic analysis

What are the major methods of hematologic evaluation?

1. Hemogram / CBC

2. Bone marrow examination

3. Immune evaluation (e.g., Coombs test)

4. Blood typing & crossmatch

5. Clotting studies

6. Flow cytometry

What are the 3 major cellular sections of a CBC?

1. Erythrogram = RBC parameters

2. Leukogram = WBC parameters

3. Thrombogram = platelet parameters

• CBC also contains miscellaneous parameters

What methods can be used to count blood cells?

• Manual

  • Hemocytometer

• Automated

  • Impedance

  • Flow cytometry

What is a Hemocytometer?

A manual method for counting blood cells using a specialized counting chamber

What is the basic principle of Impedance cell counting?

Cells pass through an aperture → cause a change in electrical impedance → the change is detected and used for cell counting/classification

What 3-part WBC differential can impedance provide?

1. Granulocytes

2. Monocytes

3. Lymphocytes

What is another major automated method used for blood-cell analysis?

Optics-based cell counting/flow cytometry.

What can the ADVIA 2120i evaluate?

1. Traditional CBC

2. 5-part differential

3. Platelet indices

4. Reticulocyte indices

Should a blood smear be evaluated as part of a CBC?

YES

Why should blood smears be made as soon as possible?

To avoid artifacts that can develop after blood collection

What type of stain is used for blood smears?

Romanowsky stain

• It uses eosin + methylene blue solutions to produce a wide range of colors

What are examples of Romanowsky stains?

1. Wright's

2. Giemsa

3. Leishman's

4. Diff-Quick

What is the most common method for making a blood smear?

Push-slide method

Comparative Blood Morphology SUMMARY

Species/Group	Important Feature
Mammals	RBC morphology varies among species
Alpaca	Distinctly oval/elliptical RBC appearance
Non-mammals	Nucleated RBCs shown
Rabbit	Heterophils
Guinea pig	Kurloff cell
Hawk	Nucleated RBCs, heterophils + thrombocytes

Anticoagulants SUMMARY

Anticoagulant	Target / Mechanism	Important Point
EDTA	Chelates Ca²⁺	Commonly used for hematology
Heparin	Activates antithrombin → inhibits thrombin	Can be useful for hematology + chemistry

Hematology Analytic Methods SUMMARY

Method	Method	Method
Hemocytometer	Manual	Manually count blood cells
Impedance	Automated	Cells passing through aperture → change electrical impedance
Flow cytometry / optical analysis	Automated	Optical detection of cells
Blood smear	Microscopic	Evaluate blood-cell morphology