Final answer:
The pectoralis minor is a muscle located beneath the pectoralis major, helping in moving the scapula and aiding in respiration by raising the ribs during deep inhalation.
Step-by-step explanation:
The pectoralis minor is a thin, triangular muscle located beneath the pectoralis major. Its primary functions include moving the scapula both downward and anteriorly and assisting in respiratory movements by raising the ribs when the scapula is stationary. As part of the anterior thorax muscles, the pectoralis minor contributes to the stabilization of the pectoral girdle, which includes the clavicles and scapulae, essential for upper limb mobility.
When engaged, the pectoralis minor pulls the scapula forward and downward toward the chest wall, playing a role in movements such as reaching down or forward. Additionally, it acts collaboratively with other muscles to secure the scapula against the thoracic wall, providing a stable base for arm movement. Its role in respiration becomes noticeable during labored breathing, where it aids in elevating the ribs to allow for an increased volume of air into the lungs.