Key Terms

ABO blood group

blood-type classification based on the presence or absence of A and B glycoproteins on the erythrocyte membrane surface

agglutination

clustering of cells into masses linked by antibodies

agranular leukocytes

leukocytes with few granules in their cytoplasm; specifically, monocytes, lymphocytes, and NK cells

albumin

most abundant plasma protein, accounting for most of the osmotic pressure of plasma

anemia

deficiency of red blood cells or hemoglobin

antibodies

(also, immunoglobulins or gamma globulins) antigen-specific proteins produced by specialized B lymphocytes that protect the body by binding to foreign objects such as bacteria and viruses

anticoagulant

substance such as heparin that opposes coagulation

antithrombin

anticoagulant that inactivates factor X and opposes the conversion of prothrombin (factor II) into thrombin in the common pathway

B lymphocytes

(also, B cells) lymphocytes that defend the body against specific pathogens and thereby provide specific immunity

basophils

granulocytes that stain with a basic (alkaline) stain and store histamine and heparin

bilirubin

yellowish bile pigment produced when iron is removed from heme and is further broken down into waste products

biliverdin

green bile pigment produced when the non-iron portion of heme is degraded into a waste product; converted to bilirubin in the liver

blood

liquid connective tissue composed of formed elements—erythrocytes, leukocytes, and platelets—and a fluid extracellular matrix called plasma; component of the cardiovascular system

bone marrow biopsy

diagnostic test of a sample of red bone marrow

bone marrow transplant

treatment in which a donor’s healthy bone marrow with its stem cells replaces diseased or damaged bone marrow of a patient

bruise

localized bleeding under the skin due to damaged blood vessels

buffy coat

thin, pale layer of leukocytes and platelets that separates the erythrocytes from the plasma in a sample of centrifuged blood

carbaminohemoglobin

compound of carbon dioxide and hemoglobin, and one of the ways in which carbon dioxide is carried in the blood

clotting factors

group of 12 identified substances active in coagulation

coagulation

formation of a blood clot; part of the process of hemostasis

colony-stimulating factors (CSFs)

glycoproteins that trigger the proliferation and differentiation of myeloblasts into granular leukocytes (basophils, neutrophils, and eosinophils)

common pathway

final coagulation pathway activated either by the intrinsic or the extrinsic pathway, and ending in the formation of a blood clot

cross matching

blood test for identification of blood type using antibodies and small samples of blood

cytokines

class of proteins that act as autocrine or paracrine signaling molecules; in the cardiovascular system, they stimulate the proliferation of progenitor cells and help to stimulate both nonspecific and specific resistance to disease

defensins

antimicrobial proteins released from neutrophils and macrophages that create openings in the plasma membranes to kill cells

deoxyhemoglobin

molecule of hemoglobin without an oxygen molecule bound to it

diapedesis

(also, emigration) process by which leukocytes squeeze through adjacent cells in a blood vessel wall to enter tissues

embolus

thrombus that has broken free from the blood vessel wall and entered the circulation

emigration

(also, diapedesis) process by which leukocytes squeeze through adjacent cells in a blood vessel wall to enter tissues

eosinophils

granulocytes that stain with eosin; they release antihistamines and are especially active against parasitic worms

erythrocyte

(also, red blood cell) mature myeloid blood cell that is composed mostly of hemoglobin and functions primarily in the transportation of oxygen and carbon dioxide

erythropoietin (EPO)

glycoprotein that triggers the bone marrow to produce RBCs; secreted by the kidney in response to low oxygen levels

extrinsic pathway

initial coagulation pathway that begins with tissue damage and results in the activation of the common pathway

ferritin

protein-containing storage form of iron found in the bone marrow, liver, and spleen

fibrin

insoluble, filamentous protein that forms the structure of a blood clot

fibrinogen

plasma protein produced in the liver and involved in blood clotting

fibrinolysis

gradual degradation of a blood clot

formed elements

cellular components of blood; that is, erythrocytes, leukocytes, and platelets

globin

heme-containing globular protein that is a constituent of hemoglobin

globulins

heterogeneous group of plasma proteins that includes transport proteins, clotting factors, immune proteins, and others

granular leukocytes

leukocytes with abundant granules in their cytoplasm; specifically, neutrophils, eosinophils, and basophils

hematocrit

(also, packed cell volume) volume percentage of erythrocytes in a sample of centrifuged blood

hematopoietic stem cell

type of pluripotent stem cell that gives rise to the formed elements of blood (hemocytoblast)

heme

red, iron-containing pigment to which oxygen binds in hemoglobin

hemocytoblast

hematopoietic stem cell that gives rise to the formed elements of blood

hemoglobin

oxygen-carrying compound in erythrocytes

hemolysis

destruction (lysis) of erythrocytes and the release of their hemoglobin into circulation

hemolytic disease of the newborn (HDN)

(also, erythroblastosis fetalis) disorder causing agglutination and hemolysis in an Rh⁺ fetus or newborn of an Rh⁻ person

hemophilia

genetic disorder characterized by inadequate synthesis of clotting factors

hemopoiesis

production of the formed elements of blood

hemopoietic growth factors

chemical signals including erythropoietin, thrombopoietin, colony-stimulating factors, and interleukins that regulate the differentiation and proliferation of particular blood progenitor cells

hemorrhage

excessive bleeding

hemosiderin

protein-containing storage form of iron found in the bone marrow, liver, and spleen

hemostasis

physiological process by which bleeding ceases

heparin

short-acting anticoagulant stored in mast cells and released when tissues are injured, opposes prothrombin

hypoxemia

below-normal level of oxygen saturation of blood (typically <95 percent)

immunoglobulins

(also, antibodies or gamma globulins) antigen-specific proteins produced by specialized B lymphocytes that protect the body by binding to foreign objects such as bacteria and viruses

interleukins

signaling molecules that may function in hemopoiesis, inflammation, and specific immune responses

intrinsic pathway

initial coagulation pathway that begins with vascular damage or contact with foreign substances, and results in the activation of the common pathway

jaundice

yellowing of the skin or whites of the eyes due to excess bilirubin in the blood

leukemia

cancer involving leukocytes

leukocyte

(also, white blood cell) colorless, nucleated blood cell, the chief function of which is to protect the body from disease

leukocytosis

excessive leukocyte proliferation

leukopenia

below-normal production of leukocytes

lymphocytes

agranular leukocytes of the lymphoid stem cell line, many of which function in specific immunity

lymphoid stem cells

type of hematopoietic stem cells that gives rise to lymphocytes, including various T cells, B cells, and NK cells, all of which function in immunity

lymphoma

form of cancer in which masses of malignant T and/or B lymphocytes collect in lymph nodes, the spleen, the liver, and other tissues

lysozyme

digestive enzyme with bactericidal properties

macrophage

phagocytic cell of the myeloid lineage; a matured monocyte

megakaryocyte

bone marrow cell that produces platelets

memory cell

type of B or T lymphocyte that forms after exposure to a pathogen

monocytes

agranular leukocytes of the myeloid stem cell line that circulate in the bloodstream; tissue monocytes are macrophages

myeloid stem cells

type of hematopoietic stem cell that gives rise to some formed elements, including erythrocytes, megakaryocytes that produce platelets, and a myeloblast lineage that gives rise to monocytes and three forms of granular leukocytes (neutrophils, eosinophils, and basophils)

natural killer (NK) cells

cytotoxic lymphocytes capable of recognizing cells that do not express “self” proteins on their plasma membrane or that contain foreign or abnormal markers; provide generalized, nonspecific immunity

neutrophils

granulocytes that stain with a neutral dye and are the most numerous of the leukocytes; especially active against bacteria

oxyhemoglobin

molecule of hemoglobin to which oxygen is bound

packed cell volume (PCV)

(also, hematocrit) volume percentage of erythrocytes present in a sample of centrifuged blood

plasma

in blood, the liquid extracellular matrix composed mostly of water that circulates the formed elements and dissolved materials throughout the cardiovascular system

plasmin

blood protein active in fibrinolysis

platelet plug

accumulation and adhesion of platelets at the site of blood vessel injury

platelets

(also, thrombocytes) one of the formed elements of blood that consists of cell fragments broken off from megakaryocytes

pluripotent stem cell

stem cell that derives from totipotent stem cells and is capable of differentiating into many, but not all, cell types

polycythemia

elevated level of hemoglobin, whether adaptive or pathological

polymorphonuclear

having a lobed nucleus, as seen in some leukocytes

positive chemotaxis

process in which a cell is attracted to move in the direction of chemical stimuli

red blood cells (RBCs)

(also, erythrocytes) one of the formed elements of blood that transports oxygen

reticulocyte

immature erythrocyte that may still contain fragments of organelles

Rh blood group

blood-type classification based on the presence or absence of the antigen Rh on the erythrocyte membrane surface

serum

blood plasma that does not contain clotting factors

sickle cell disease

(also, sickle cell anemia) inherited blood disorder in which hemoglobin molecules are malformed, leading to the breakdown of RBCs that take on a characteristic sickle shape

T lymphocytes

(also, T cells) lymphocytes that provide cellular-level immunity by physically attacking foreign or diseased cells

thalassemia

inherited blood disorder in which maturation of RBCs does not proceed normally, leading to abnormal formation of hemoglobin and the destruction of RBCs

thrombin

enzyme essential for the final steps in formation of a fibrin clot

thrombocytes

platelets, one of the formed elements of blood that consists of cell fragments broken off from megakaryocytes

thrombocytopenia

condition in which there are too few platelets, resulting in abnormal bleeding (hemophilia)

thrombocytosis

condition in which there are too many platelets, resulting in abnormal clotting (thrombosis)

thrombopoietin

hormone secreted by the liver and kidneys that prompts the development of megakaryocytes into thrombocytes (platelets)

thrombosis

excessive clot formation

thrombus

aggregation of fibrin, platelets, and erythrocytes in an intact artery or vein

tissue factor

protein thromboplastin, which initiates the extrinsic pathway when released in response to tissue damage

totipotent stem cell

embryonic stem cell that is capable of differentiating into any and all cells of the body; enabling the full development of an organism

transferrin

plasma protein that binds reversibly to iron and distributes it throughout the body

universal donor

individual with type O⁻ blood

universal recipient

individual with type AB⁺ blood

vascular spasm

initial step in hemostasis, in which the smooth muscle in the walls of the ruptured or damaged blood vessel contracts

white blood cells (WBCs)

(also, leukocytes) one of the formed elements of blood that provides defense against disease agents and foreign materials