Hematology Basics: Blood Components, Cells & Collection

These vocabulary flashcards cover fundamental terms related to blood composition, cellular elements, hematologic disorders, and common veterinary blood-collection practices.

Blood

A specialized connective tissue consisting of cells suspended in an extracellular matrix called plasma.

Plasma

Liquid portion of blood that contains clotting factors; requires an added anticoagulant to prevent clotting.

Serum

The liquid that remains after blood has clotted and clotting factors have been removed.

Red Blood Cell (RBC) / Erythrocyte

An anucleate, biconcave cell packed with hemoglobin that transports oxygen.

Reticulocyte

Immature RBC released from bone marrow; larger and contains less hemoglobin than a mature erythrocyte.

Hemoglobin (Hb)

The oxygen-carrying protein found inside red blood cells.

Central Pallor

The lighter-colored central region of an RBC caused by its biconcave shape.

Biconcave Disc

Characteristic shape of mammalian RBCs that increases surface area for gas exchange.

Erythrocytosis

An increased number of circulating red blood cells; may result from bone-marrow overproduction or chronic hypoxia.

Anemia

A decrease in red blood cell mass or hemoglobin concentration.

Regenerative Anemia

An anemia in which bone marrow response is adequate, shown by increased reticulocytes; often due to blood loss.

Non-regenerative Anemia

An anemia caused by bone-marrow failure to produce sufficient RBCs.

White Blood Cell (WBC) / Leukocyte

A cell of the immune system; divided into granulocytes and agranulocytes.

Leukocytosis

An increased total white blood cell count.

Leukopenia

A decreased total white blood cell count.

Granulocyte

A leukocyte that includes neutrophils, eosinophils, and basophils.

Neutrophil

The most abundant leukocyte; first responder that performs phagocytosis of bacteria and debris.

Band Neutrophil

An immature neutrophil with a non-segmented nucleus.

Left Shift

Presence of increased band neutrophils in circulation, indicating heightened demand for neutrophils.

Neutrophilia

An increased number of circulating neutrophils.

Neutropenia

A decreased number of circulating neutrophils.

Eosinophil

Granulocyte that combats parasites and modulates allergic reactions; contains pink granules.

Eosinophilia

An increased eosinophil count.

Eosinopenia

A decreased eosinophil count.

Basophil

Granulocyte involved in parasite defense and allergic responses; releases histamine and has purple granules.

Basophilia

An increased basophil count.

Basopenia

A decreased basophil count.

Agranulocyte

Leukocyte lacking prominent cytoplasmic granules; includes monocytes and lymphocytes.

Monocyte

The largest leukocyte; phagocytic cell that can differentiate into macrophages or dendritic cells in tissues.

Macrophage

Tissue-resident phagocyte derived from monocytes that ingests pathogens and dead cells.

Dendritic Cell

Antigen-presenting cell derived from monocytes that initiates adaptive immune responses.

Monocytosis

An increased monocyte count.

Monocytopenia

A decreased monocyte count.

Lymphocyte

Second most common leukocyte; central to adaptive immunity (includes B and T cells).

B Cell

Lymphocyte that differentiates into plasma cells and produces antibodies.

Plasma Cell

Antibody-secreting effector cell derived from a B cell.

T Cell

Lymphocyte responsible for cell-mediated immunity; includes cytotoxic and helper subtypes.

Cytotoxic T Cell

T cell that directly kills virus-infected or abnormal cells.

Helper T Cell

T cell that coordinates immune responses by activating B cells, cytotoxic T cells, and macrophages.

Lymphocytosis

An increased lymphocyte count; may be stress-induced.

Lymphopenia

A decreased lymphocyte count.

Platelet / Thrombocyte

Small anucleate cell fragment involved in hemostasis; forms the primary platelet plug.

Thrombocytosis

An increased platelet count.

Thrombocytopenia

A decreased platelet count that can lead to bleeding and bruising.

Jugular Vein

Neck vein commonly used for high-volume or high-pressure blood collection.

Cephalic Vein

Front-limb vein frequently catheterized in dogs and cats for blood sampling.

Lateral Saphenous Vein

Outer hind-limb vein used for blood draws, especially in dogs.

Medial Saphenous Vein

Inner hind-limb vein often used for blood collection in cats and small animals.

Purple Top Tube

Vacutainer containing EDTA anticoagulant; used for complete blood counts (CBC).

Green Top Tube

Vacutainer containing heparin anticoagulant; used for chemistry panels on plasma.

Blue Top Tube

Vacutainer containing citrate anticoagulant; used for coagulation studies.

Red blood Tube

Vacutainer with no additives; allows clot formation for serum chemistry tests.

Blood Smear

Microscopic preparation used to evaluate the morphology of blood cells.