No other muscle is as prominent in a youthful and fit appearance as a strong and developed chest. What most people consider as the chest is composed of two muscles, the pectoralis major, and the pectoralis minor. Below is a brief description of these muscles and their primary purpose.
The pectoralis major is a large, substantial, fan-shaped muscle that makes up the majority of the chest muscle mass. It originates at your clavicle, ribs, and sternum, and inserts into the upper portion of your humerus (upper arm bone from elbow to shoulder.) The pectoralis major helps flex the shoulder joint, and moves your arm toward and across your chest. This is the muscle that gives the chest that strong and fit appearance in a front and side profile.
The pectoralis minor is a thin, triangular muscle that is found underneath the pectoralis major. It attaches at the 3rd, 4th and 5th rib, and it reaches to the scapula (shoulder blade.). It is not a very large muscle but is gives the pectoralis major more prominence when it is developed and strong. Its job is to help pull the shoulder forward and down.
When exercising the chest I like to use a heavy movement to develop the pectoralis major followed by a lighter shaping exercise to target the pectoralis minor. Thus, combining an exercise to build mass with a movement to shape and define the chest. Below is a video of two of my favorite exercises to accomplish this task.