Answer:
Floating ribs
Explanation:
The thoracic cavity has 12 pairs of ribs evenly distributed on the left and the right sides of the cavity that function to provide surface area for muscle attachment such as the intercoatal muscles that assist in breathing. The ribs are flat shaped bones semi circular in shape attaching to the thoracic vertabrae with a wider. The first to the tenth ribs are linked to the sternum by a cartilage to assist in their epansion and relaxation during breathing. The 11th and 12th ribs have no cartilage that can attach them to the sternum and hence are called floating ribs.
