Final answer:
A normal adult has 12 pairs of ribs amounting to 24 ribs total, which make up the thoracic cage and protect vital organs. True ribs (1-7) attach directly to the sternum, while false ribs (8-10) and floating ribs (11-12) do not.
Step-by-step explanation:
Normal Adult Ribs Count
In a normal adult, there are 12 pairs of ribs, totaling 24 ribs altogether. These ribs form the thoracic cage, which not only provides structure to the thorax or chest region but also protects critical organs such as the heart and lungs. The ribs are connected posteriorly to the thoracic vertebrae and anteriorly to the sternum via costal cartilages, except for the 11th and 12th pairs, which are known as floating ribs and do not attach to the sternum.
The first seven pairs of ribs are termed true ribs because they connect directly to the sternum. Ribs 8 through 10, defined as false ribs, connect to the sternum indirectly through cartilage that is joined to the rib above. The floating ribs (11 and 12) are not connected to the sternum at all. These various attachments allow for the expansion and flexibility necessary for respiration.