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single-celled organisms that lack a nucleus; much smaller in size than human cells


blood cells that specialize in transporting oxygen and carbon dioxide; also called red blood cells (RBCs)


blood cells that specialize in fighting infection; also called white blood cells


a form of agranular leukocytes that are the key players in fighting infection; include T cells and B cells


a form of agranular leukocytes that are actively phagocytic and may transform into macrophages


the cellular process of engulfing a foreign substance; performed by neutrophils, monocytes, and eosinophils


red blood cells, which are the most abundantly formed elements of blood; provide transport of oxygen due to the presence of the protein hemoglobin within the cells


process of blood-cell formation within the red bone marrow


an abundant protein in red blood cells that has a high bonding affinity for oxygen and carbon dioxide


the status of being immune, or successfully resistant to infection


a yellowish fluid channeled through lymphatic capillaries, vessels, and trunks; similar in composition to plasma

lymph nodes

pea-sized organs filled with white blood cells that filter out foreign materials from the lymph; nodes that are actively fighting an infection often swell, producing swollen glands that can be felt to aid in a diagnosis

lymphatic capillaries

microscopic, blind-ended vessels into which interstitial fluid diffuses; are present in most tissues and often parallel blood capillaries

lymphatic nodules

clusters of lymphatic tissue; composed of white blood cells that are embedded within the walls of the large intestine; also known as Peyer's patches

lymphatic trunk

large vessels that carry lymph to the subclavian veins near the heart

lymphatic vessels

vessels that carry lymph from lymphatic capillaries to lymphatic trunks; similar in structure to veins; link lymph nodes to form a chain that leads toward the heart


type of white blood cell that plays the primary role in conferring immunity; forms the bulk of lymphatic tissue; includes T cells and B cells


any microorganism that causes disease, such as a virus, bacterium, protozoan, or fungus


formed elements that are fragments of whole cells; also known as platelets; perform the primary role in coagulation to form blood clots

thymus gland

the soft organ located in the chest superior to the heart in which some white blood cells (known as T lymphocytes) become mature before entering circulation; also part of the endocrine system


a poisonous substance produced by a cell or tissue that affects various parts of the body


presence of red blood cells of unequal size


presence of bacteria in the bloodstream


abnormally reduced number of red blood cells


rupture of the red blood cell membrane


loss of blood from the circulation


abnormally large-sized red blood cells


large, irregularly shaped red blood cells


abnormal increase in the number of erythrocytes in the blood


abnormal enlargement of the spleen


presence of toxins in the bloodstream


acronym for acquired immune deficiency syndrome; AIDS is caused by the human immunodeficiency virus (HIV), which disables the immune response by destroying mainly helper T cells (needed for activation of B cells); the loss of immune function allows opportunistic infections to proliferate and eventually cause death


response to an allergen, which is an antigen that produces a hypersensitivity reaction that includes immediate inflammation but does not elicit other immune responses; allergies are of many types, the most common of which are allergic rhinitis (hay fever), which affects mucous membranes of the nasal cavity and throat, and allergic dermatitis, which affects the skin where it has made contact with the allergen


an immediate reaction to an antigen that includes rapid inflammation and system-wide smoothmuscle contraction


a reduced ability of red blood cells to deliver oxygen to tissue; common forms of anemia include aplastic anemia, iron deficiency anemia, sickle cell, and pernicious anemia


anemia characterized by the failure of red bone marrow to produce red blood cells

Autoimmune disorder

any one of several diseases that are caused by a person's own immune response attacking otherwise healthy tissues; diseases include rheumatoid arthritis, systemic lupus erythematosus, and multiple sclerosis


form of poisoning caused by the ingestion of food contaminated with toxin produced by the bacterium Clostridium botulinum


disease caused by a bacterium and its toxin; results in inflammation of mucous membranes primarily in mouth and throat


general term for an abnormal condition of the blood

Erythroblastosis fetalis

blood disorder that results from incompatibility between a fetus with Rh positive blood and its mother with Rh negative blood; causes the destruction of fetal red blood cells and requires blood transfusion to save the fetus; also known as Rh mismatch or hemolytic disease of newborn


fungal infection distributed by way of the bloodstream

Gas gangrene

Infection of a wound caused by various anaerobic bacteria; produces a fermentation gas, necrosis, and septicemia


inherited disorder that results in an excessive accumulation of iron deposits in the body


inherited bleeding disorder that results from defective clotting proteins involved in blood coagulation
• Hemophilia is the oldest known hereditary bleeding disorder

Hodgkin's disease

cancer of lymphatic tissue; characterized by the progressive enlargement of lymph nodes, fatigue, and deficiency of the immune response


condition that results from a defective immune response


reduction of an immune response caused by disease or, in the case of organ transplants, by the use of chemical, pharmacologic, physical, or immunologic agents


multiplication of disease-causing microorganisms


a swelling of body tissue caused by movement of plasma into the extracellular space to produce edema, or fluid accumulation in tissue; symptoms include swelling, redness, heat, and pain


viral disease characterized by a temporary inflammation of mucous membranes and fever; commonly called "the flu," the virus is highly contagious and is capable of mutating to escape detection by B and T memory cells

Iron deficiency anemia

anemia that is caused by a lack of iron, which results in smaller red blood cells that contain deficient levels of hemoglobin


cancer of the red bone marrow, which is the blood forming tissue


inflammation of the lymph nodes


disease of the lymph nodes; this general term is often applied to a syndrome, lymphadenopathy syndrome (LAS), which is a persistent swelling of the lymph nodes that often precedes the onset of AIDS


tumor that originates in lymphatic tissue


disease caused by a parasitic protozoan that is carried by Anopheles mosquitoes and infects red blood cells; characterized by periodic fever and fatigue


viral disease characterized by enlarged lymph nodes, an increase in number of mononuclear blood cells (monocytes and lymphocytes), sore throat, fever, and fatigue


bone-marrow disorder characterized by the proliferation of abnormal stem cells; usually develops into a form of leukemia

Nosocomial infection

a disorder—usually bacterial infections—contracted during a hospital stay; often due to antibiotic resistant strains of Staphylococcus

Pernicious anemia

anemia caused by an inadequate supply of folic acid (vitamin B12), resulting in red blood cells that are large, varied in shape, and reduced in number


any infectious disease of wide prevalence or excessive mortality; also refers specifically to an acute infectious disease caused by the bacterium Yersinia pestis and characterized by high fever, skin eruptions, internal hemorrhage, and pneumonia; also called bubonic plague


bacterial infection spread from the mouth of an infected animal, usually by way of a bite; this bacterium produces a neurotoxin that acts on the central nervous system and is highly fatal


a systemic disease caused by the presence of bacteria and their toxins in the circulating blood; a person suffering from this is referred to as "septic"

Sickle cell anemia

inherited, chronic anemia that is characterized by defective hemoglobin, which causes red blood cells to become misshapen (sickle-shaped), resulting in drowsiness, leg ulcerations, fever, joint and abdominal pain, and thrombosis


presence of Staphylococci bacteria in the blood, which is the literal meaning of the term; commonly called a staph infection, it is a frequent complication to normal healing and also the most common cause of food poisoning, skin inflammation, osteomyelitis, and nosocomial infections


disease caused by a powerful neurotoxin released by the common bacterium Clostridium tetani; the toxin acts upon the central nervous system to cause convulsions and paralysis


tumor that originates in the thymus gland


therapeutic treatment in which a substance with known toxicity to bacteria is administered; may be obtained from mold (fungus) or from other bacteria; effective only against bacteria, and many types of bacteria are capable of developing resistance, especially when antibiotics are not administered properly


chemical agent that reduces the clotting process

Antiretroviral therapy

application of drugs to battle against a class of viruses that tend to mutate quickly, known as retroviruses, of which HIV is a member; also known as combination therapy, the drugs form a cocktail that includes nucleoside analog reverse transcriptase inhibitors and protease inhibitors, all of which block HIV replication by a variety of means


process in which pathogens are rendered less virulent, prior to their incorporation into a vaccine preparation

Autologous transfusion

transfusion of blood donated by a patient for personal use; this is a common procedure before a surgery to avoid potential incompatibility or contamination


the field of science and medicine focused on the study of bacteria and prevention of bacterial diseases; one who specializes in this field is a bacteriologist

Blood chemistry

test or series of tests on plasma to measure the levels of particular components (glucose, albumin, cholesterol, etc.)

Blood culture

test to determine infection in the blood by placing a blood sample on a nutritive media in an effort to grow populations of bacteria for analysis

Blood transfusion

introduction of blood, blood products, or blood substitute into a patient's circulation to restore blood volume to normal levels; the two main types of blood transfusions are autologous transfusion and homologous transfusion

Coagulation time

a timed blood test to determine the time required for a blood clot to form; one type of this test, called prothrombin time (PT) measures the time required for prothrombin, a precursor protein, to form thrombin and is often used to monitor anticlotting therapy; another type of test is partial thromboplastin time (PTT), which is used to evaluate clotting ability

Complete blood count

a common laboratory blood test that provides diagnostic information of a patient's general health; includes several more specific tests including hematocrit, hemoglobin, red blood count, and white blood count

Differential count

microscope count of the number of each type of white blood cell, using a stained blood smear

Erythrocyte sedimentation rate

a timed test to measure the rate at which red blood cells fall through a volume of plasma to provide information on their hemoglobin content; commonly used to evaluate nonspecific systemic inflammation


test that measures the percentage of red blood cells in a volume of blood; obtained from centrifuging a sample of blood to separate blood cells


the general field of medicine that focuses on blood related disease


test that measures the level of hemoglobin in red blood cells


stoppage of bleeding

Homologous transfusion

transfusion of blood that is voluntarily donated by another person; requires blood-type matching known as cross matching to prevent incompatibility


procedure that provides immunity against a particular antigen


the study concerned with immunity and allergy


a treatment of infectious disease; the use of agents (serum, gamma globulin, treated antibodies, etc.) to activate or strengthen the immune response

Lymph node dissection

removal of lymph nodes for pathological study to assist in a diagnosis; also known as a lymph node biopsy


excision of a lymph node


process of x-ray photography of the lymph nodes following injection of a contrast medium


incision into a lymph node


process of x-ray photography of lymphatic vessels following injection of a contrast medium; produces an x-ray recording called a lymphangiogram


removal of a donor's blood, which is then separated into blood components, with one portion retained for use and the remainder returned to the donor; includes plasmapheresis, in which plasma is used, leukapheresis, in which white blood cells are used, and plateletpheresis, in which platelets are used

Platelet count

calculation of the number of platelets in the blood


any treatment that tends to prevent the onset of an infection or other type of disease

Red blood count

measures the number of red blood cells per cubic centimeter


excision of the spleen


surgical fixation of the spleen


process of dissolving a blood clot


excision of the thymus gland


field of study that focuses on the study and treatment of toxins and the diseases they cause; one who specializes in this field is a toxicologist


inoculation of a culture that has reduced virulence as a means of providing a cure or a prophylaxis


any preparation used to activate an immune response


field of study that focuses on the study of viruses and the diseases they cause; one who specializes in this field is a virologist

White blood count

measures the number of white blood cells per cubic centimeter


vital body fluid that transports substances necessary for survival by way of the cardiovascular system; consists of: plasma, formed elements


is a straw-colored, clear liquid that is 90 percent water. Besides water, plasma contains dissolved salts and minerals such as calcium, sodium, magnesium, and potassium. Microbe-fighting antibodies travel to the battlefields of disease by hitching a ride in the plasma.


protein of blood plasma that begins the blood clotting process


blood plasma that is lacking fibrinogen

Formed elements

substances suspended in the fluid (blood); 3 types include: RBCs, WBCs & platelets

Red blood cells (RBCs)

or erythrocytes—the most abundant cells; carry hemoglobin, a specialized protein that contains iron molecules, which enable the protein to bind to oxygen & carbon dioxide; RBCs are produced by stem cells in the red bone marrow during hematopoiesis


or thrombocytes—the 2nd most abundant type of blood cell; platelets are actually fragments from huge cells that break apart during development in the bone marrow; perform the role of preventing fluid loss by releasing proteins in a process known as coagulation, which results in the formation of blood clots

White blood cells (WBCs)

or leukocytes—the fewest cells in a normal blood sample; perform an important role in protecting your body from infectious microorganisms and other foreign, unwanted materials; there are several types, depending on their histological features.


granulocytes because they contain tiny, pebble-like objects in their cytoplasm (their granules stain red); actively attack and "eat" bacteria and unwanted cells in a process known as phagocytosis


granulocytes because they contain tiny, pebble-like objects in their cytoplasm (their granules stain blue); release substances that trigger an allergic reaction


granulocytes because they contain tiny, pebble-like objects in their cytoplasm (their granules stain pink in a neutral stain); neutrophils, the most abundant, actively attack and "eat" bacteria and unwanted cells in a process known as phagocytosis


large agranulocytes that are aggressive "eaters" of bacteria and other unwanted cells, especially once they transform into macrophages


smaller agranulocytes that provide you with the most powerful immune reaction of the body; include B & T cells

B cells

are produced in the bone marrow & also mature there; produce the most effective weapon in the fight against infection—tiny molecules called antibodies; antibodies attach to unwanted substances called antigens, rendering them ineffective

T cells

capable of destroying unwanted substances by a variety of means and are important in activating the B cells.

Precursors of T cells

produced in the bone marrow, leave the bone marrow and mature in the thymus

Lymphatic system

closely associated with the blood and its circulation; the system also includes components that play a key role in protecting the body against infection; consists of vessels and a yellowish liquid known as lymph, which flows in a one-way direction toward the heart;

Main functions of lymph system

• Recycling fluid back to the bloodstream
• Fighting infection with the white blood cells it contains

organs of the lymphatic system include:

• Microscopic lymphatic capillaries
• Lymphatic vessels—deliver lymph into larger channels
• Lymphatic trunks
• Lymph nodes—pea-sized organs that lymph enters from the lymphatic vessels
• Spleen—located in the abdominal cavity
• Thymus gland—located in the chest
• Tonsils—three pairs in the throat
• Lymphatic nodes—embedded in the wall of the large intestines

The immune response

is a mechanism in the body employed to battle infections, which are immunological diseases that result from pathogens (disease-causing agents that include viruses, bacteria, fungi, protozoans, and worm-like organisms).

Pathogens may cause harm via __, __.

• By destroying cells
• By releasing toxins (poisonous substances) that interfere with cell function

The immune response

is a series of reactions against infection that are orchestrated by white blood cells:

Immune response series of rx

• Unwanted pathogens are attacked by white blood cells that are phagocytic; the process occurs mainly within the lymphatic organs and often results in inflammation, which produces redness, swelling, heat, and pain at the infectious site
• If the infection is aggressive, phagocytosis cannot control the invaders alone; in this case, lymphocytes are brought to battle by chemical signals—the phagocytes produce chemical signals that result in rapid growth of lymphocyte populations; two different mechanisms of lymphocyte activation take place during an infection.

Cytotoxic T cells

help rid the body of cells that have been infected by viruses as well as cells that have been transformed by cancer.
• T cells also are responsible for the rejection of tissue and organ grafts.

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