The thoracic cage protects the organs that are contained within it.
Protect the heart and lungs.
The answer is "cone-shape" noted in the Lab Book A&P CAT VERSION Eliane Marieb page 137
1. breathing 2. protect viscera in the thoracic+abdominal cavities 3. support pectoral girdle and upper limbs
I had this for my anatomy class, and my teacher told us it was an upside down ice cream cone.