Final answer:
The manubrium of the sternum attaches to the clavicle at the sternoclavicular joint and to the first ribs, providing connection and structural support for the upper chest area.
Step-by-step explanation:
The manubrium of the sternum serves as an important site of attachment for various structures within the thoracic region. Notably, the clavicular notch located on the superior-lateral margins of the manubrium is where the sternoclavicular joint is formed. Here, the sternal end of the clavicle, commonly referred to as the collarbone, articulates with the manubrium. Additionally, the manubrium attaches to the first ribs, providing further structural integrity to the thoracic cage. The junction where the manubrium and the body of the sternum meet is known as the sternal angle, which is also the site where the second ribs attach. The sternoclavicular joint represents the only bony connection between the pectoral girdle of the upper limb and the axial skeleton, highlighting its significance for both support and mobility.