The major muscles that are divided during resuscitative thoracotomy include the pectoralis major, the pectoralis minor, and the serratus anterior muscles.

• Pectoralis major muscle: It originates from the anterior surface of the medial half of the clavicle, the anterior surface of the sternum, and the cartilages of all of the true ribs (the first seven ribs which are directly attached to the sternum). The 5-cm wide tendon inserts into the upper humerus.

• Pectoralis minor muscle: It arises from the third, fourth, and fifth ribs, near their cartilages, and inserts into the coracoid process of the scapula.

• Serratus anterior muscle: It originates from the first eight or nine ribs and inserts into the medial part of the scapula.

The left phrenic nerve descends on the lateral surface of the pericardium.

The lower thoracic aorta is situated to the left of the vertebral column. The esophagus descends on the right side of the aorta to the level of the diaphragm, where it moves anterior and to the left of the aorta. The aorta is the first structure felt while sliding your fingers along the left posterior wall anterior to the spine.