The rib cartilage that forms the rib arch is the anterior cartilage of the 8th-10th ribs. The anterior end of the 8th rib is connected to the anterior end of the 7th rib by cartilage, the anterior end of the 9th rib is connected upward to the anterior end of the 8th rib cartilage, and the anterior end of the 10th rib is also connected upward to the anterior end of the 9th rib, thus forming the rib arch. The ribs are divided into true ribs, false ribs, and floating ribs, with the front of ribs 1-7 attached to the sternum by cartilage, and the front of ribs 8, 9, and 10 attached upward to the front of the superior cartilage, with the attachment sites moving backward in sequence to create a curved rib arch structure. The 11th and 12th ribs, called floating ribs, are free at the anterior end and are not connected to any bone or cartilage; the ribs form a barrel-shaped structure through the sternum and the posterior spine to form the thoracic cavity.