It gives attachment to the linea alba, the midline of the abdomen. They are floating ribs. Clavicles aren't part of the thoracic cage but articulate medially with the manubrium. Lateral ends articulate with scapulae forming shoulder girdle. Iliac bones meet with sacrum on posterior.
Pelvic girdle attaches to several postural muscles.
Also, muscles pertaining to respiration take their origin on the pelvic girdle. Breathing refers to the mechanical process of moving air into and out of the lungs. It also is the mechanical process for generating sound into the upper aspect of the respiratory tract. The rings hold the trachea open. Posterior wall has trachealis muscle to fill the gap between the C-rings.