The upper limbs are attached to the pectrol gridles . These are very light and allow the upper limbs a degree of mobility not seen anywhere else in the body . The gridle is formed of two halves . Each half of the pectrol gridle consists of a clavicle or collar bone and a scapula . The scapula is a large , thin, triangular bone situated in the dorsal surface of the ribcage between the second and seventh ribs It has a slightly elevated ridge called the spine which projects as a flat , expanded process called the acromion . The clavicle articulates with this process . Below the acromion is a depression called the glenoid cavity which articulates with the head of the hum erus to form the shoulder joint . Each clavicle which lies horizontally and connects axial skelton with appendicular skeleton .
