Final answer:
The second costocartilage attaches to the sternum at the sternal angle, the junction between the manubrium and the body of the sternum.
Step-by-step explanation:
The second costocartilage connects to the sternum at the sternal angle. The sternum is the elongated bony structure that anchors the anterior thoracic cage and consists of three parts: the manubrium, body, and xiphoid process. The manubrium and body join together at the sternal angle, which is the junction line between the two and serves as the site for attachment of the second rib. Importantly, the sternal angle is a significant anatomical landmark as it marks the level where the second rib attaches, which helps in identifying and counting the lower ribs.