Final answer:
The tensional elements of the axial skeleton are the vertebral column and thoracic cage, which are essential for body support, protection of internal organs, and maintenance of upright posture.
Step-by-step explanation:
The tensional elements of the axial skeleton include the vertebral column and thoracic cage, and are said to be preloaded. These structures are crucial parts of the axial skeleton, which forms the central axis of the body. The vertebral column plays a fundamental role in maintaining the upright posture of the body and transmits the weight from the upper parts of the body to the lower extremities. In addition, the thoracic cage, composed of the ribs and sternum, protects the vital organs in the chest such as the heart and lungs.
Among the option provided (a. thoracic cage and vertebral column, b. thoracic cage and pectoral girdle, c. skull and pelvic girdle, d. pectoral and pelvic girdles), the correct answer is a. thoracic cage and vertebral column. The bones of the axial skeleton, along with muscles and ligaments, contribute to the tensional element of the structure, supporting the body and allowing for complex movements.