What is the term for the area of the chest marked by rib cage outlines?

The term that describes the area of the chest marked by the outlines of the rib cage is "costal." This term specifically refers to the ribs and is derived from the Latin word "costa," meaning rib. The costal area includes the tissues and structures associated with the ribs, which protect vital organs such as the heart and lungs and assist in the mechanics of breathing.

In contrast, "sternal" refers to the region of the chest that pertains to the sternum, or breastbone, which is located in the center of the thoracic area. The sternal region is not marked by the outlines of the rib cage but rather by the sternum itself. "Thoracic" describes a broader region of the body that encompasses the entire chest cavity, including both the costal and sternal regions, along with organs and structures contained within the thorax. "Abdominal" pertains to the area of the body below the thorax, thus not relevant to the chest area defined by rib outlines.