Abscess -- A localized accumulation of pus buried in tissues, organs, or confined spaces, usually caused by a bacterial infection.

Anemia -- A condition in which there are not enough healthy red blood cells to carry adequate oxygen to tissues. The cause may be an iron or vitamin deficiency, blood loss, a chronic illness, a genetic or acquired defect or disease, or a side effect of medication.

Antibody -- Any of the protein molecules produced by specialized immune system cells (B cells) that can recognize and bind to a particular foreign antigen. If the antigen is on the surface of a cell, this binding leads to cell aggregation and subsequent destruction. Antibodies are also referred to as immunoglobulins.

Antigen -- A substance that induces the formation of antibodies because the immune system recognizes it as a threat. It may be a foreign substance from the environment, such as chemicals, or formed within the body, such as bacterial or viral toxins.

Brucellosis -- An infectious disease caused by the bacteria of the genus Brucella. Humans become infected by coming in contact with animals or animal products that are contaminated with these bacteria. Brucellosis can cause a range of symptoms that are similar to the flu and may include fever, sweats, headaches, back pains, and physical weakness.

Capillary -- Any of the minute vessels connecting the arterioles and venules, forming a network in nearly all parts of the body. Their walls act as semi-permeable membranes for the interchange of various substances, including fluids, between the blood and tissue.

Embryo -- The end product of the zygote that eventually becomes the offspring, during their period of most rapid development, defined as from the time the long axis appears until all major structures are represented. In humans, the embryo is this developing organism from approximately the fourth day after fertilization to the end of the eighth week.

Embryology -- The science of the development of the individual during the embryonic stage, or in the stages immediately preceding or following it.

Endothelium -- The layer of epithelial cells that lines the cavities of the heart, the lumina of blood and lymph vessels, and the serous cavities of the body.

Epithelioid -- Resembling epithelium, the cell layer covering the internal and external surfaces of the body, including the lining of vessels and other small cavities.

Hill-Burton Act, or the Hospital Survey and Construction Act -- Enacted in 1946, the Hill-Burton Act was designed to provide grants to states and local governments in order to modernize hospitals that suffered from under-funding during the Depression and World War II. Since 1946, it has resulted in the allocation of over $4.6 billion to build or repair over 4,000 facilities around the United States.

Histology -- The subset of the study of anatomy that deals with the minute structures, composition, and function of the tissues.

Immune systems -- A complex system of cellular and molecular components that primarily function as the body's defense against foreign organisms or substances. The principal cellular components are lymphocytes and macrophages, and the primary molecular components are antibodies and lymphokines.

Lesion -- An abnormal change in the structure of an organ or tissue due to injury or disease, especially one that is circumscribed or well defined.

Leukemia -- A progressive, malignant disease of the blood-forming organs, characterized by distorted proliferation and development of white blood cells and their precursors in the blood and bone marrow.

Leukocyte -- Any of several types of colorless blood cells capable of ameboid movement. Also called "white blood cells" or "white cells," they are important components of the immune system.

Lymphatic system -- The lymphoid tissue of the body considered collectively. It can be divided into primary lymphoid tissues, the thymus or bone marrow where lymphocytes differentiate from stem cells, and secondary tissues, the lymph nodes, spleen, and other lymphoid tissue, such as the tonsils, where lymphocytes take part in immune responses.

Lymphocyte -- Any of the mononuclear, nonphagocytic leukocytes, found in the blood, lymph, and lymphoid tissues, which are the body's immunologically competent cells and their precursors.

Mesenchyme, or mesenchyma -- The meshwork of loosely organized embryonic connective tissue in the mesoderm from which is formed the connective tissues of the body, as well as the blood vessels and lymphatic vessels.

Microphage -- A small phagocyte such as neutrophil, an abundant type of white blood cell highly destructive of microorganisms.

Monocyte -- A large, phagocytic mononuclear white blood cell with very fine granulation in the cytoplasm. Monocytes constitute about three to eight percent of the white blood cells in humans.

Mononuclear cells -- Cells having a singular nucleus, especially a monocyte of the blood or tissues.

Multinucleate cells -- A cell having two or more nuclei, such as neutrophil, a type of white blood cell.

Pathology -- That branch of medicine that treats of the essential nature of the disease, especially of the structural and functional changes in tissues and organs of the body that are caused by disease.

Phagocyte -- A cell, such as a white blood cell, that engulfs and absorbs waste material, harmful microorganisms, or other foreign bodies in the bloodstream and tissues.

Puerperal fever, or childbed fever -- A form of septicemia generally caused by streptococcus, accompanied by fever, in which the focus of the infection is the uterus.

Synthetic media -- A nutrient-rich environment in which microbes are grown that is chemically defined by very precise amounts of each ingredient.

Syphilis -- An acute to chronic infectious disease caused by the spirochete Treponema pallidum, which is usually transmitted by sexual contact or acquired in utero.

Tuberculosis -- Any of the infectious diseases of humans or other animals caused by species of Mycobacterium and characterized by the formation of tubercles and caseus necrosis in the tissues. In humans, the most common form is pulmonary tuberculosis, which if untreated, can result in tuberculous pneumonia, tuberculous granulation tissue, caseous necrosis, calcification, and cavity formation. Symptoms include weight loss, fatigue, night sweats, and wasting, with purulent or bloody sputum, and chest pain.

White blood cells, or leukocytes -- A colorless blood cell capable of amoeboid movement. There are several different types, classified into the two large groups, granular leukocytes (basophils, eosinophils, and neutrophils), and nongranular leukocytes (lymphocytes and monocytes).