The Thoracic Skeleton and Walls

The thorax is the upper part of the trunk and contains the heart and lungs and the structures associated with them — the large blood vessels, the trachea and bronchi. The oesophagus also passes through the thorax in or near the midline from the neck to the abdominal cavity, as do two autonomic structures, the vagus nerve and the sympathetic trunk on each side. The phrenic nerves pass from the neck through the thorax to the diaphragm. The thoracic walls, moved by muscles, expand and contract during respiration. The diaphragm, lying between the thoracic and abdominal cavities, makes a large contribution to the changes in volume of the thoracic cavity during this activity. The conical shape of the thorax can only be appreciated after removal of the pectoral girdle, formed by the scapula and clavicle, and the muscles which attach the upper limb to the trunk.