[Calcifying aponeurotic fibroma of the right shoulder in an infant]

The muscles surrounding the shoulder girdle, including the clavicle and scapula, primarily stabilize the scapula. This stable base allows other muscles to move the humerus effectively. Scapular movements often mirror those of the humerus and extend its range of motion. For instance, raising the arm above the head would not be feasible without simultaneous upward rotation of the scapula.
Anterior Thoracic Muscles
The anterior thoracic muscles include the serratus anterior, subclavius, and...

The upper and lower limb initially develops as a small bulge called a limb bud, which appears on the lateral side of the early embryo. The upper limb bud appears near the end of the fourth week of development, with the lower limb bud appearing shortly after.
Initially, the limb buds consist of a core of mesenchyme covered by a layer of ectoderm. The ectoderm at the end of the limb bud thickens to form a narrow crest called the apical ectodermal ridge. This ridge stimulates the underlying...

Nine muscles are involved in arm movements. Two of these, the pectoralis major and latissimus dorsi, originate from the axial skeleton and are called axial muscles. The other seven originate from the scapula and are called the scapular muscles.
The pectoralis major has two origins. Its clavicular head originates on the medial half of the clavicle. In contrast, the sternocostal head originates on the costal cartilages of ribs 1-6, the sternum, and the aponeurosis of the external oblique of the...