The |sternum| is a flat, blade-like bone located at the center of the chest. It serves as the ~anterior~ (forward) site of articulation for the |ribs| via cartilaginous connections, called |costal cartilage|. The |pectoralis major| also anchors to the |sternum|, giving the |shoulder joint| much of its strength during ~flexion~ of the arm. The |sternum| features two articulations in addition to its ~costal~ (rib) articulations. One of these, called the manubriosternal joint, is between the body (middle plate) of the |sternum| and the broader upper section, called the manubrium. The manubrium of the |sternum| articulates with the |clavicles| and the |sternocleidomastoid|, |sternohyoid|, and |sternothyroid| muscles connect here. The lower articulation is called the xiphisternal joint, and is between the body of the |sternum| and a small, teardrop-shaped bone called the xiphoid (pronounced "zy'-foid") ~process~. The xiphoid ~process~ anchors the |rectus abdominis|, the ~transverse~ thoracic, and the |diaphragm| muscles, responsible for much of the muscular expansion and |contraction| of the abdomen.
