There are two muscles found in the thoratic wall of the cat that  are not found in humans. Those two are, the xiphihumeralis and the  pectiantebrachiales.
Sternum - Structure. 1  The sternum is a long, flat bone, forming the middle portion of the front of the chest. 2  Manubrium. 3  Xiphoid process. 4  In its natural position, the sternum is angled obliquely, downward and forward. 5  The manubrium (Latin: handle) is the broad upper part of the sternum. It has a quadrangular shape, narrowing from the top, which gives it four borders. The suprasternal notch (jugular notch) is located in the middle at the upper broadest part of the manubrium. This notch can be felt between the two clavicles. On either side of this notch are the right and left clavicular notches. The manubrium joins with the body of the sternum, the clavicles and the cartilages of the first pair of ribs.
The sternum or breastbone is a long flat bone shaped like a necktie located in the center of the chest. It connects to the ribs via cartilage, forming the front of the rib cage, and thus helps to protect the heart, lungs, heart and major blood vessels from injury. The sternum is consists of three regions: the manubrium, the body, and the xiphoid process. The word sternum originates from the Greek ÏÏÎ­ÏÎ½Î¿Î½, meaning chest.