Largest Chest Muscle 💪 Pectoralis major is the superior most and largest muscle of the chest. #PectoralisMajor is a thick, fan-shaped muscle that lies underneath the breast tissue and forms the anterior wall of the axilla (armpit). . Chest Muscle Human Anatomy . There are five muscles of the chest. From superficial to deep, these are the external intercostal, internal intercostal, innermost intercostal, subcostal (posteriorly), and transverse thoracic (anteriorly). These muscles change the volume of the thoracic cavity for respirtion to occur. They elevate or depress the ribs, increasing the thoracic volume and vital (breathing) capacity. . Superficial muscles to the thoracic wall function in the movement of the shoulder girdle, thoracic wall, and spine. These muscles include the #pectoralis major and minor, serratus anterior, levatores costarum (elevators of the ribs), extensor muscles of the spine, and serratus posterior superior and inferior. . The diaphragm is an important muscle for respiratory function. The diaphragm forms the inferior border of the thoracic cavity separating the abdomen from the thorax. As the muscle contracts, it increases the volume of the thoracic cavity resulting in inspiration. Later in pregnancy, the developing baby can raise the volume of the abdominal cavity, thereby reducing vital capacity. . Other muscles that have attachments to the thoracic wall but act predominantly as extensions to the thorax include the scalene, sternocleidomastoid, and subclavius muscles superiorly. Muscles extending inferiorly include quadratus lumborum, psoas major/minor, external oblique, internal oblique, transversus abdominis, and rectus abdominis muscles. #chestmuscle #humananatomy #pectoralismajor #samsulek