Anatomy of the ribs. There are 12 ribs on each side. All 12 connect posteriorly with the vertebrae of the spine. Ribs 1–7 connect anteriorly directly to the sternum, while ribs 8–10 attach to the superior costal cartilages. Ribs 11 and 12 are floating ribs with no anterior attachment. The intercostal vein, artery, and nerve run in the costal groove, which is located along the inferior border of each rib.

Anterior chest wall

• Pectoralis major muscle: The origin is the anterior surface of the medial half of the clavicle and the anterior surface of the sternum. It inserts into the upper humerus. The blood supply is the pectoral branch of the thoracoacromial trunk.

• Pectoralis minor muscle: The origin of the muscle is on the third through fifth ribs near their cartilages. It inserts into the coracoid process of the scapula.

Lateral chest wall

• Serratus anterior muscle: The origin is the lateral part of the first 8–9 ribs. It inserts into the medial aspect of the scapula.

Posterior chest wall

• Latissimus dorsi muscle: The origin is the spinous processes of the lower thoracic spine and posterior iliac crest. It inserts into the upper portion of the humerus.

• Trapezius muscle: The origin of the trapezius muscle is large, from the occipital bone down through the spinous processes of T12. It inserts on the lateral third of the clavicle and the scapula.

• Erector spinae muscle: The origin is the spinous processes of T9–T12 vertebrae and the medial slope of the iliac crest.

• Access to fractures underlying the scapula is obtained through the “auscultatory triangle” between the superior edge of the latissimus dorsi, the lateral border of the trapezius, and the inferomedial border of scapula.