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Module Overview


This module will provide students with:

After completion of this module, students will be able to:


The blood of man and domestic animals has been studied for many years.  It is not until recently that avian hematology has taken its place as a valuable tool to diagnose and control disease.   The examination of the avian blood smear is a very crucial part of the routine hematological assessment.  In some very small species of birds, such as hummingbirds, only a very minute amount of blood can be obtained, and the differential may be the single diagnostic procedure that can be done.  The differential can provide information on disease processes such as anemia, liver disease, malignancies, inflammatory diseases and many others.  For this reason, it is very important for a veterinary technician student to learn to perform this diagnostic procedure.


These hematological terms are used throughout this module; they appear in blue with links back to this glossary.

Anisocytosis - The presence of red blood cells showing excessive variation in size

Anticoagulant - A substance that inhibits the clotting of the blood

Basophilic - Refers to cells that stain readily with blue dyes

Chromatin - The material within the cell nucleus from which chromosomes are formed

Diagnosis - Identification of a disease or condition by a scientific evaluation of physical signs, symptoms, history, laboratory tests, and procedures

Differential - Distinguishing the different types of blood cells

Eccentric - Off-centered

Eosinophilic - Refers to cells that stain readily with red dyes

Erythrocyte - Red blood cell

Granulocyte - A cell containing cytoplasmic granules

Hematology - The study of blood

Hematoma - A localized accumulation of blood between tissues or tissue layers, due to a break in a blood vessel

Hemostasis - The termination of bleeding with mechanical or chemical means        

Hemostatic Agent - An agent that stops bleeding

Heparin - A naturally occurring anticoagulant

Hypochromia - Reduced hemoglobin content

Leukocyte - White blood cell

Mononuclear - Pertaining to one nucleus

Morphology - The study of the structure and form of a blood cell

Necropsy - A postmortem examination performed to confirm or determine the cause of death of an animal

Peripheral blood - Blood outside of the bone marrow that is carrying blood to and from the heart and lungs in blood vessels

Poikilocytosis - The presence of red blood cells showing excessive variation in shape

Polychromia - Red cells staining with a basophilic tinge, indicating incomplete hemoglobin formation

Prognosis - A prediction of the probable outcome of a disease

Proximal - Pertaining to a position toward the body proper

Psittacine - Pertaining to parrots

Vacuole - A clear or fluid-filled space or cavity within a cell

Venipuncture - The puncturing of a vein for blood withdrawal

Ventral - Pertaining to a position toward the belly of the body; frontward; anterior


Relevance to Academia and Industry

The number of veterinarians treating exotic animals has increased greatly over the last ten years.  These veterinarians depend on laboratory results to help establish a diagnosis, track the course of a disease, and offer a prognosis to clients.  Veterinary technicians are heavily relied upon to perform many of the avian diagnostic procedures. The avian differential is one of the most critical of these hematologic tests.  This module should prove useful in training technicians entering the veterinary field, and to assist those that are currently practicing in the field to become more knowledgeable and proficient when performing a differential.