The chest consists of the chest wall, the heart and its large blood vessels, and both lungs. The chest wall consists of the rib cage, the sternum, and the spine forming a bony framework. Then inside the bony framework there are intercostal muscles, outside there are muscles such as pectoralis major, pectoralis minor, latissimus dorsi, rhomboid, and erector spinae, and outside the muscles there are subcutaneous tissues and skin. These tissues and structures enclose the structure of the thorax. Inside the thorax, there is the mediastinum, which consists of the heart and its large blood vessels; above the thorax, there is the thymus, which begins to degenerate and form mechanization after puberty; then the thoracic cavity on both sides consists of both lungs and their blood vessels. The thorax is protective of the heart and lungs inside the thorax.