The trapezius muscle (Trapz) is a large muscle consisting of four parts covering the upper back, shoulders and neck. It is used in shrugging the shoulders and with overhead movements.
There are two rhomboid muscles - Rhomboid Major and Rhomboid Minor. Rhomboid major is larger and positioned below rhomboid minor. Chins and dips are excellent activities for developing these muscles.
The Pectoralis Minor muscle is the smallest of the two pectoral (chest) muscles. It works together with Serratus anterior which protracts and rotates the scapula upwards. When the two work together, pure protraction (without rotation) is produced.
The Serratus Anterior muscle is used in activities which draw the scapula forwards. It is used strongly in push-ups and bench presses. Winged scapula are an indicator of having a weak Serratus Anterior muscle.