No, not all ribs directly articulate with the sternum. Ribs 1 to 7 directly articulate with the sternum, while ribs 8 to 10 indirectly articulate with the sternum through the costal cartilages of the ribs above them. Ribs 11 and 12 are floating ribs that do not articulate with the sternum at all.
There are 12 pairs of ribs that articulate with the thoracic vertebrae, one per vertebra. The upper 7 pairs of ribs articulate directly with the sternum, either via their own costal cartilage or the cartilage of the rib above. Ribs 8-10 articulate indirectly with the sternum through a shared cartilage, while ribs 11 and 12 are floating ribs that do not connect to the sternum.
Floating ribs (ribs 11 and 12) do not articulate with the sternum directly but are attached only to the thoracic vertebrae in the back. They are considered "floating" because they lack an attachment to the sternum or cartilage.
Because they do not articulate directly onto the vertebrae.
According to Ross and Wilson Anatomy and Physiology, 2 pairs
True ribs
costal cartilage.
The clavicles and ribs are lateral to the sternum. Both bones articulate with the breastbone.
Ribs are classified according to their attachment to the sternum. The first seven pairs of ribs attach directly to the sternum and are called true ribs. Ribs 8-10 have cartilage that attaches to the cartilage of the seventh rib and are called false ribs. The eleventh and twelfth ribs do not attach to the sternum and are called floating ribs.
Only the true ribs are attached to the sternum the false ribs (3) and the floating ribs (2) are not directly attached. The flalse ribs are attached indirectly via cartillage and the floating ribs are not attached at all.
Most people have 12 pairs of ribs in their ribcage. The top 7 pairs are true ribs, attached directly to the sternum, while the bottom 5 pairs are false ribs, either attaching indirectly to the sternum or not at all.
The first seven ribs connect directly to the sternum via costal cartilage. These ribs are known as "true ribs" or vertebrosternal ribs.