The thoracic wall consists mainly of bones and muscles. It is formed by:

• Anteriorly: the sternum. The sternum is a bone that consists of three parts: manubrium of sternum, body of sternum, and the xiphoid process.

• Laterally: twelve ribs on each side and three layers of muscles, which fill the intercostal spaces between adjacent ribs. These muscles move the ribs and provide mechanical support for the intercostal spaces.

• Posteriorly: twelve thoracic vertebrae and their intervertebral discs.

The skeletal framework of the chest wall provides a rich amount of attachment sites for muscles of the neck, abdomen, back, and upper limbs. Some of these muscles attach to ribs and function as accessory respiratory muscles, and some of them also stabilize the positions of the 1st and last ribs.