ANATOMY OF THE CLAVICLE (COLLARBONE)

The two clavicles, also called your collarbones, are long bones found between your sternum and scapulae. They are found just above the first rib and help hold the scapula in place. This lets the arm hang freely away from the thorax and have a larger range of movement.
The clavicle and scapula together make up the shoulder girdle, also called the pectoral girdle. The clavicle forms the anterior portion of the shoulder girdle, which serves to connect the arms to each side. The shoulder girdle also transmits physical impacts from the upper limb to the axial skeleton, which includes bones of the head and trunk.
At its medial end, the clavicle articulates with the manubrium of the sternum at the sternoclavicular joint. At its lateral end, the clavicle articulates with the acromion of the scapula at the acromioclavicular joint. The two ends of the clavicle are easily distinguished – the medial end is rounded or prismatic and the lateral end is flattened. The inferior surface of the lateral end is rough and has a ridge called the trapezoid line, also called the oblique or trapezoid ridge, which attaches to the trapezoid ligament. Medial to the trapezoid ridge is a slight rounded projection called the conoid tubercle, also called the coracoid tuberosity, which is overtop the coracoid process of the scapula. Note that the coracoclavicular ligament, which connects the clavicle to the coracoid process, is made up of two fasciculi – the trapezoid ligament and the conoid ligament.
The clavicle can be divided into three parts: the medial or sternal end, the shaft, and the lateral or acromial end. The medial end articulates with the clavicular notch of the manubrium of the sternum, forming the sternoclavicular joint. The shaft can be divided into the medial two thirds, which is thicker and a lateral one third. The lateral third has two borders and two surfaces. The borders are the concave, thin, rough anterior border and the convex, rough, thicker posterior border. The surfaces are upper and lower.

Model from: https://www.turbosquid.com/FullPrevie...