mellizom

Mellizom, meaning “pectoralis muscle” in Hungarian, refers to the chest muscles located on the anterior thorax, most often the pectoralis major and pectoralis minor. Together, they form the front wall of the chest and contribute to movements of the shoulder girdle and arm.

Pectoralis major is a broad, fan-shaped muscle covering the upper chest. It has a clavicular head that originates from the medial half of the clavicle and a sternocostal head that originates from the sternum and the upper six costal cartilages. The muscle inserts into the intertubercular groove of the humerus. Its actions include flexion, adduction, and medial rotation of the humerus; the clavicular portion favors flexion of a raised arm, while the sternocostal portion contributes to moving a flexed arm toward the body. Innervation comes from the medial and lateral pectoral nerves of the brachial plexus. Blood supply is provided by branches of the thoracoacromial trunk (pectoral branches) and the lateral thoracic artery.

Pectoralis minor lies beneath the major and originates from ribs 3–5, inserting on the coracoid process of the scapula. It stabilizes the scapula by drawing it anteriorly and inferiorly toward the thoracic wall and can assist in deep inspiration when the scapula is fixed. Innervation is via the medial pectoral nerve, with possible small communications from the lateral pectoral nerve. Blood supply comes from perforating branches of intercostal arteries and related thoracoacromial branches.

Clinically, these muscles contribute to shoulder movement and posture. Imbalances or tightness can affect scapular mechanics, while weakness can influence pressing or pulling activities.