anthrax A highly infectious disease that normally affects animals, especially ruminants (such as cattle, sheep, and horses), but that can be transmitted to humans by contact with infected animals or their products or by biologic warfare. The agent of anthrax is the bacterium Bacillus anthracis. Its spores can resist destruction and remain viable for years….
anthracosis See black lung disease.
anterior pituitary See pituitary, anterior.
anterior cruciate ligament A ligament in the knee that crosses from the underside of the femur to the top of the tibia. Abbreviated ACL. Injuries to the ACL can occur in a number of situations, including sports, and can be quite serious, sometimes requiring surgery. See also knee.
antenatal diagnosis See prenatal diagnosis.
antagonist A substance that acts against and blocks an action. Antagonist is the opposite of agonist. Antagonists and agonists are key players in the chemistry of the human body and in pharmacology.
ant sting See fire ant.
anoxia The absence, or near absence, of oxygen. Anoxia can injure tissues of the body.
anotia The absence from birth of the external, visible part of the ear (the auricle).
anosmia The failure of the development of or the loss of the sense of smell.
anorgasmia Failure to achieve orgasm (climax) during sexual intercourse. Anorgasmia has many causes, including stress, anxiety, depression, fatigue, worry, guilt, fear of painful intercourse, fear of pregnancy, the undesirability of a partner, the undesirability of a setting, and the use of alcohol or prescription or illicit drugs.
anorexigenic Causing anorexia (loss of appetite) as, for example, an anorexigenic drug. See also anorexia.