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Habituation to a specific practice, such as drinking alcoholic beverages or using drugs (for example, heroin, cocaine, or amphetamines), and disorders characterized by the chronic use of a drug, alcohol, or similar substance. Addiction and addictive…

A disease of the nervous system characterized by a progressive dementia that leads to profound impairment in cognition and behavior. Dementia occurs in a number of brain diseases where the impairment in cognitive abilities represents a decline from…

Loss of sensation with or without loss of consciousness. Anesthesia is used to prevent pain during surgery and other medical procedures. There are several ways of producing anesthesia, with the choice dependent on the type of surgery and the medical…

Any treatment or procedure that includes the in-vitro handling of oocytes (immature ova or egg cells) and sperm or embryos for the purpose of establishing a pregnancy. Assisted reproductive technology (ART) is undertaken as a treatment of…

Bats are members of the order Chiroptera, which is the second-largest order of living mammals. The geographic distribution of these flying mammals is tremendous as well, ranging from the limit of trees in the Northern Hemisphere to the southern tips…

The common name for a malignant neoplasm or tumor. Cancer is a serious medical condition that develops when the orderly relationship of cell division and cell differentiation becomes disordered, leading to the development of neoplasms. Neoplasms are…

Cells within a tumor that possess the capacity to self-renew and cause the heterogeneous lineages of cancerous cells that comprise the tumor. Cancer stem cells (CSCs) typically represent a small percentage of all cells in a tumor (rarely more than…

The administration of chemical substances for the treatment of disease, especially cancer, or for the prevention of aberrant growth of cells or tissues (neoplasms). In general, chemotherapy is the use of chemicals to treat any disease, but the term…

Pathologies and abnormal conditions that involve the circulatory system. Circulation disorders include both localized disturbances of circulation and diseases of the circulatory system (Fig. 1). Circulation 1 Illustration of the thickening and…

Structural or functional abnormalities of the body that develop during embryogenesis and the fetal period; also called birth defects. Congenital anomalies, or birth defects, are conditions present at or from birth that deviate from the body's normal…

Any of a group of diseases involving connective tissue as the pathological target. Connective tissue comprises one of the primary tissues of the body and is distinguished by an abundance of fibrillar and nonfibrillar extracellular components, which…

Any of a group of viruses that cause upper and lower respiratory tract diseases, gastroenteritis, hepatitis, and central nervous system infections in birds and mammals, including humans. Coronaviruses (Fig. 1) comprise a major group of common animal…

A genome-engineering technique that allows precise targeting of specific stretches of genetic code and editing of DNA at designated locations. The CRISPR/Cas9 system has been used as a general tool to engineer the genomes of many different…

A pathology characterized by abnormal enlargement of air spaces distal to the terminal bronchioles in the lung. Emphysema (see illustration) is a pathologic condition distinguished by loss of elasticity of the lung. The primary cause of this loss of…

The occurrence of cases of disease in excess of what is usually expected for a given period of time. An epidemic is a breakout of disease affecting unusually large numbers of people within a community or population. When an epidemic spreads…

An organism that has had its genetic material manipulated or altered in a laboratory setting through the use of genetic or genomic engineering techniques. Genetically modified organisms (GMOs) are microorganisms, plants, or animals that have been…