The thorax is formed primarily by which structures?

The thorax is formed primarily by which structures?

• A. Sternum and ribs
• B. Clavicle and scapula
• C. Humerus and radius
• D. Pelvis

Answer: (A)

The chest wall is built mainly from the sternum and the ribs, which together with their costal cartilage form the thoracic cage that encases the heart and lungs and enables breathing by expanding and contracting. The sternum sits in the front, providing a central anchor for the ribs, while the ribs curve around to meet the sternum and attach to the thoracic vertebrae at the back. The clavicle and scapula belong to the shoulder girdle, not the thoracic enclosure. The humerus and radius are arm bones, and the pelvis is part of the lower trunk, so they do not form the thorax.

The chest wall is built mainly from the sternum and the ribs, which together with their costal cartilage form the thoracic cage that encases the heart and lungs and enables breathing by expanding and contracting. The sternum sits in the front, providing a central anchor for the ribs, while the ribs curve around to meet the sternum and attach to the thoracic vertebrae at the back. The clavicle and scapula belong to the shoulder girdle, not the thoracic enclosure. The humerus and radius are arm bones, and the pelvis is part of the lower trunk, so they do not form the thorax.