Definition of Terms for Hematology

plasminogen

protein converted to plasmin to dissolve thrombi and clots

plasma

liquid portion of blood

phagocytosis

process of cellular ingestion and digestion of foreign bodies

oxyhemoglobin

combined form of oxygen and hemoglobin; primarily found in arterial blood

neutrophil

fully mature WBC capable of phagocytosis; primary defense against bacterial infection

natural killer (NK) cells

lymphocytes that defend against microorganisms and malignant cells

myelopoiesis

formation and maturation of cells derived from myeloid stem cell

myeloid

pertaining to nonlymphoid blood cells that differentiate into RBCs, platelets, macrophages, mast cells, and various WBCs

monocyte

large WBC that becomes a macrophage when it leaves the circulation and moves into body tissues

macrophage

reticuloendothelial cells capable of phagocytosis

lymphoid

pertaining to lymphocytes

lymphocyte

form of WBC involved in immune functions

leukopenia

less-than-normal amount of WBCs in circulation

leukocyte

one of several cellular components of blood involved in defense of the body; subtypes include neutrophils, eosinophils, basophils, monocytes, and lymphocytes (synonym: white blood cell [WBC])

hemostasis

intricate balance between clot formation and clot dissolution

hemoglobin

iron-containing protein of RBCs; delivers oxygen to tissues

hematopoiesis

complex process of the formation and maturation of blood cells

hematocrit

percentage of total blood volume consisting of RBCs

granulocyte

granulated WBC (i.e., neutrophil, eosinophil, basophil)

fibrinolysis

process of breakdown of fibrin clot

fibrinogen

protein converted into fibrin to form thrombus and clot

fibrin

filamentous protein; basis of thrombus and blood clot

erythropoietin

hormone produced primarily by the kidney; necessary for erythropoiesis

erythropoiesis

process of the formation of RBCs

erythrocyte

a cellular component of blood involved in the transport of oxygen and carbon dioxide (synonym: red blood cell [RBC])

differentiation

development of functions and characteristics that are different from those of the parent stem cell

cytokines

proteins produced by leukocytes that are vital to regulation of hematopoiesis, apoptosis, and immune responses

blast cell

primitive white blood cell (WBC)

band cell

slightly immature neutrophil

anemia

decreased red blood cell (RBC) count

platelet

a cellular component of blood involved in in blood coagulation (synonym: thrombocyte)

red blood cell (RBC)

a cellular component of blood involved in the transport of oxygen and carbon dioxide (synonym: erythrocyte)

reticulocytes

slightly immature RBCs, usually 1% of total circulating RBCs

reticuloendothelial system

complex system of cells throughout the body capable of phagocytosis

serum

portion of blood remaining after coagulation occurs

stem cell

primitive cell, capable of self-replication and differentiation into myeloid or lymphoid cell

stroma

component of the bone marrow not directly related to hematopoiesis but serves important supportive roles in this process

thrombocyte

a cellular component of blood involved in blood coagulation (synonym: platelet)

white blood cell (WBC)

one of several components of blood involved in the defense of the body; subtypes include neutrophils, eosinophils, basophils, monocytes, and lymphocytes (synonym: leukocyte)

absolute neutrophil count (ANC)

a calculation of the number of circulating neutrophils, derived from the total number of white blood cells and the percentage of neutrophils counted in a microscope’s visual field

aplasia

lack of cellular development (e.g., cells within the bone marrow)

erythroid cells

any cell that is or will become a mature RBC

haptoglobin

blood protein synthesized by the liver; binds free hemoglobin released from erythrocytes which is then removed by the reticuloendothelial system

hemolysis

destruction of RBCs with release of cellular components into the circulation; may occur within or outside the vasculature

hemosiderin

iron-containing pigment derived from the breakdown of hemoglobin

hypochromia

pallor within the RBCs caused by decreased hemoglobin content

leukemia

uncontrolled proliferation of WBCs

lymphopenia

a lymphocyte count less than 1500/mm³

megaloblastic anemia

a type of anemia characterized by abnormally large, nucleated RBCs

microcytosis

smaller-than normal RBCs

neutropenia

lower-than-normal number of neutrophils

normochromic

normal RBC color, indicating normal amount of hemoglobin

normocytic

normal size of RBC

pancytopenia

abnormal decrease in WBCs, RBCs, and platelets

petechiae

tiny capillary hemorrhages

poikilocytosis

variation in shape of RBCs

polycythemia

excess in RBCs

spherocytes

small, spherically shaped RBCs

thrombocytopenia

lower-than-normal platelet count

thrombocytosis

higher-than-normal platelet count