Question

Why are some costae called "false ribs?"

A) They are located outside of the chest cavity.
B) They are actually made of cartilage instead of bone.
C) They attach only to other ribs or have no attachment.
D) They are attached to the sternum with ligaments instead of cartilage.

Answer 1

Some costae are called 'false ribs' because they do not attach directly to the sternum. Instead, their costal cartilages attach either indirectly to the next higher rib or terminate within the musculature of the abdominal wall. The correct option is D) They are attached to the sternum with ligaments instead of cartilage.

Step-by-step explanation:

Ribs 1-7 are classified as true ribs (vertebrosternal ribs). The costal cartilage from each of these ribs attaches directly to the sternum. Ribs 8-12 are called false ribs (vertebrochondral ribs).

The costal cartilages from these ribs do not attach directly to the sternum. For ribs 8-10, the costal cartilage is attached to the cartilage of the next higher rib.

Thus, the cartilage of rib 10 attaches to the cartilage of rib 9, rib 9 then attaches to rib 8, and rib 8 is attached to rib 7. The last two false ribs (11-12) are also called floating ribs (vertebral ribs). These are short ribs that do not attach to the sternum at all. Instead, their small costal cartilages terminate within the musculature of the lateral abdominal wall. The correct option is D) They are attached to the sternum with ligaments instead of cartilage.