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A compound in red blood cells that affects oxygen binding to and release from hemoglobin.


Destruction of part or all of an organ or structure.


A purulent collection of fluid separated from surrounding tissue by a wall consisting of inflammatory cells and adjacent organs. It usually contains necrotic debris, bacteria, and inflammatory cells.


A primary-generalized seizure characterized by sudden and brief (i.e., several seconds in duration) loss of consciousness without muscle movements.

Acanthosis nigricans:

Increased thickness and hyperpigmentation of the outer cell layers of the skin; typically observed at areas of flexure.


A chemical that kills mites and ticks.


A hepatotoxic metabolic by-product of alcohol.


The neurotransmitter responsible for transmitting messages between certain nerve cells in the brain.


Disorder in which the esophageal sphincter is impaired, preventing normal swallowing and often causing reflux of contents and a feeling that something is caught in the throat.


Absence of free hydrochloric acid in the stomach.


An increase in the hydrogen ion concentration of the blood or a fall below normal in pH.


Any pathologic state that leads to acidemia.

Acinar cells:

Exocrine glands of the pancreas that secrete digestive enzymes.


A pathologic condition characterized by excessive production of growth hormone during adulthood after epiphyseal (long bone) fusions have completed.

Action potential:

A rapid change in the polarity of the voltage of a cell membrane from negative to positive and back to negative; a wave of electrical discharge that travels across a cell membrane.

Acute acid-base disorder:

An acid-base disturbance that has been present for minutes to hours.

Acute coronary syndrome (ACS):

Ischemic chest discomfort at rest most often accompanied by ST-segment elevation, ST-segment depression, or T-wave inversion on the 12-lead electrocardiogram; caused by plaque rupture and partial or complete occlusion of the coronary artery by thrombus. Acute coronary syndromes include myocardial infarction and unstable angina.

Acute kidney injury:

Characterized by a rapid decrease in kidney function and the resultant accumulation of nitrogenous waste products (e.g., creatinine and blood urea nitrogen or BUN), with or without a decrease in urine output.

Acute otitis media:

Inflammation of the middle ear accompanied by fluid in the middle ear space and signs or symptoms of an acute ear infection.

Acute respiratory distress syndrome (ARDS):

Occurs when fluid builds up in the alveoli of the lungs, reducing amount of oxygen delivered to other organs.

Acute tubular necrosis:

Form of acute kidney injury that results from toxic or ischemic injury to the cells in the proximal tubule of the kidney.


A primary, chronic, neurobiologic disease, with genetic, psychosocial, and environmental factors influencing its development and manifestations. It is characterized by behaviors that include one or more of the following: impaired control over substance use, compulsive use, continued use despite harm, and craving.


A non-malignant tumor of the epithelial tissue that is characterized by glandular structures.

Adenomatous polyposis coli (APC):

A gene associated with familial adenomatous polyposis (FAP), an inherited disorder characterized by ...

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