There are three segmental nomenclature methods commonly used to describe the anatomy of the mitral apparatus: Carpentier nomenclature, anatomic nomenclature, and Duran nomenclature. The Carpentier system has been adopted by the American Society of Echocardiography (ASE) Nomenclature and Standards Committee and the Society of Cardiovascular Anesthesiologists (SCA) to standardize the nomenclature of leaflet segments. In contrast, the Duran nomenclature system helps us understand the mitral apparatus because this system is based on the division of tendons between papillary muscle and leaflet segments. 1, ASE-SCA nomenclature: (Carpentier) specifies the three sectors of the posterior leaflet as P1 (posterior), P2 (middle), and P3 (anterior). the P1 (posterior) sector is adjacent to the anterolateral union and is closest to the left auricle. the P3 sector is adjacent to the posterior medial union. This nomenclature specifies the three corresponding regions of the anterior lobe as A1 (P1 contralateral), A2 (P2 contralateral), and A3 (P3 contralateral). 2, anatomical nomenclature: the posterior lobe includes three fan-shaped surfaces: lateral (anterior), middle and medial (posterior). The lateral (anterolateral) sector is closest to the left heart ear. For convenience of description alone, the anterior lobe is accordingly divided into three parts: lateral, middle, and medial. The anterolateral papillary muscle extends the tendon cords connecting the anterior mitral leaflet and the lateral half of the posterior mitral leaflet, respectively. Thus, the middle scalloped surface of the posterior leaflet and the middle part of the anterior leaflet are connected to the two papillary muscles by tendons. 3. Duran nomenclature: The system names the posterior leaflets as P1 (lateral, nearest to the left auricle), PM (middle), and P2 (anterior, adjacent to the posterior medial union) based on the distribution of the tendon cords. Corresponding to the middle sector (PM) connecting the anterior (M1) posterior (M2) papillary tendon cords, the middle sector was further divided into PM1 and PM2. the anterior lobe was divided into two zones, A1 and A2, corresponding to the area of the anterior-posterior papillary muscle connecting the tendon cords. In addition, two parts of the joint zone of the valve were designated as C1 (anterolateral, between A1 and P1) and C2 (posterior medial, A2 and P2).