The Left Atrium

Abstract

The terminology of the atria has been confusing. The words, auricle, atrium, and appendix (or appendage) are often interchanged. Auricle (L. auricula = ear) has long been used—presumably because of the fancied resemblance of the protuberance of the right-sided chamber to the ear of a dog. In the Grays Anatomy of 1893, the word auricle denoted the entirety of each chamber (right or left) which was divided into two parts, sinus and appendix. Approximately 4 decades later in Cunninghams Textbook of Anatomy (1931), the word atrium denoted the entirety of each chamber—however, the protuberances were termed the auricles. Today, another 4 decades later, in some medical writings auricle denotes the entire chamber, which is divided into atrium and appendix. Most authors use only the terms atrium and atrial appendage (auricle is discarded)—this practice is followed in this work. Use of the Greek word atrium, which roughly denotes the room where one pauses before entering the main hall, seems appropriate although the end diastolic volume of the left atrium is less than the stroke volume—i.e., the chamber acts as more than an atrium but also as a conduit during ventricular filling. The word left atrium denotes, herein, either the entire chamber when used in a general sense— or the chamber minus the appendage when anatomic relationships are described.