Final answer:
The first seven ribs, known as true ribs, attach directly to the sternum through their costal cartilage, which is a hyaline cartilage structure essential for attachment. True ribs form the front part of the ribcage, providing protection to the thoracic organs.
Step-by-step explanation:
The first seven ribs are referred to as true ribs or vertebrosternal ribs. These ribs are notable for being directly connected to the sternum through their costal cartilage. Costal cartilage is a hyaline cartilage structure essential for the attachment of the ribs. The true ribs, numbered 1-7, have cartilages that attach straight to the sternum, forming the forepart of the ribcage. This structural arrangement provides protection to the thoracic cavity and its vital organs such as the heart and lungs.
While the true ribs attach directly to the sternum, the remaining ribs—numbers 8 through 12—are known as false ribs or vertebrochondral ribs. They attach indirectly to the sternum or not at all. Ribs 8 to 10 are connected to each other through cartilage, which then attaches to the cartilage of rib 7. Lastly, ribs 11 and 12 are also often called floating ribs because they are not attached to the sternum or to the anterior ribcartilage.