Final answer:
The medial pectoral nerve functions to innervate the pectoralis minor and the medial part of the pectoralis major, facilitating movement and stabilization of the pectoral girdle and upper limbs.
Step-by-step explanation:
The function of the medial pectoral nerve (C8, T1) is to innervate the pectoralis minor and sternal portion (medial part) of the pectoralis major muscle. These muscles are located in the anterior thorax and are crucial for the movement and stabilization of the pectoral girdle and upper limbs. The pectoralis minor helps with the protraction and depression of the scapula, which moves the shoulder downward and anteriorly, while the pectoralis major assists in the adduction and medial rotation of the humerus, effectively moving the upper limb across the chest.