Dictionary

Body systems

Anatomy and the conditions of each body system, from the heart and lungs to the skin.

arteriovenous graftA soft synthetic tube placed under the skin to join an artery to a vein, used for hemodialysis access.

arteryA blood vessel that takes blood from the heart out to the body.

arthritisInflammation of one or more joints.

ascitesA buildup of fluid in the abdominal cavity, the space around the organs of the belly.

aspirationBreathing food, liquid, saliva or stomach contents into the airway and lungs; also, drawing fluid out with suction or a needle.

aspiration pneumoniaPneumonia that develops after food, liquid, stomach contents or saliva are breathed into the lungs.

asthmaA long-term lung disease in which the airways become inflamed and narrow from time to time.

asthma attackA sudden worsening of asthma in which the airways tighten, swell and fill with mucus.

asystoleA complete absence of electrical activity and pumping in the heart; a flat line on the monitor.

ataxiaLoss of control and coordination of body movements, so that movements are clumsy and unsteady.

atelectasisThe collapse of part or all of a lung, in which the tiny air sacs close and hold no air.

atherosclerosisA buildup of fatty deposits (plaque) inside the walls of the arteries.

atopic dermatitisA long-term inflammatory skin condition in which the skin barrier is weak; the most common type of eczema.

ATPAdenosine triphosphate: the molecule that stores and delivers energy for nearly every process in a cell.

ATPaseAdenosine triphosphatase: an enzyme that breaks down ATP to release energy the cell uses.

atrialRelating to an atrium, one of the two upper chambers of the heart.

atrial fibrillationAn irregular heart rhythm in which the upper chambers of the heart quiver instead of beating in an organized way.

atrial septal defectA hole in the wall between the two upper chambers of the heart.

atriumOne of the two upper chambers of the heart, which receive blood coming back to the heart.

atrophyThe wasting away or shrinking of a body part, such as a muscle or organ.

attention deficit hyperactivity disorderA brain development condition that affects attention, activity level and self-control, starting in childhood.

auditoryRelating to hearing or to the ear.

auricleThe outer part of the ear that you can see, on the side of the head.

autism spectrum disorderA lifelong difference in brain development that shapes how a person communicates, relates to others and experiences the world.

autoimmuneDescribing a reaction in which the immune system attacks the body's own healthy cells and tissues.

autoimmune diseaseA disease in which the immune system attacks the body's own healthy tissue.

autonomicWorking on its own, without conscious control; used for the nerves that run the organs.

autonomic nervous systemThe part of the nervous system that controls body functions without conscious thought, such as heart rate, breathing and digestion.

AV nodeAtrioventricular node: a small group of cells between the upper and lower chambers of the heart that passes on the heartbeat signal.

axonThe long, thin part of a nerve cell that carries electrical signals away from the cell body.