Dictionary

atrophic vaginitis Thinning of the lining (endothelium) of the vagina due to decreased production of estrogen. Atrophic vaginitis may occur with menopause.

atrium An entry chamber. On both sides of the heart, the atrium is the chamber that leads to the ventricle.

atrioventricular node The electrical relay station between the upper and lower chambers of the heart. Abbreviated AV node. Electrical signals from the atria must pass through the AV node to reach the ventricles. The AV node, which controls the heart rate, is one of the major elements in the cardiac conduction system. The AV node…

atrioventricular Pertaining to the upper chambers of the heart (atria) and the lower chambers of the heart (ventricles).

atrial septum The wall between the right and left atria of the heart.

atrial septal defect A hole in the wall (septum) between the upper chambers of the heart (atria). Abbreviated ASD. ASD is a major class of heart malformation. Usually, when clots in veins break off (embolize), they travel first to the right side of the heart and then to the lungs, where they lodge. When there…

atrial fibrillation See fibrillation, atrial.

atrial arrhythmia See arrhythmia, atrial.

atria The plural of atrium.

atresia Absence of a normal opening, or failure of a structure to be tubular. Atresia can affect many structures in the body. For example, esophageal atresia is a birth defect in which part of the esophagus is not hollow, and with anal atresia, there is no hole at the bottom end of the intestine.

ATP 1 Acute thrombocytopenic purpura. 2 Adenosine triphosphate.

atopic dermatitis A skin disease characterized by areas of severe itching, redness, scaling, and loss of the surface of the skin. Atopic dermatitis is the most common of the many types of eczema. Atopic dermatitis is frequently associated with other allergic disorders, especially asthma and hay fever. A defect of the immune system within the…