The abductor pollicus brevis (APB) muscle is primarily associated with which nerve?

The abductor pollicis brevis (APB) muscle is primarily associated with the median nerve because this nerve is responsible for the motor innervation of the muscles in the thenar eminence, which includes the APB. The function of the APB is to abduct the thumb, an essential movement for grasping and manipulating objects. The median nerve originates from the brachial plexus and innervates several important muscles in the forearm and hand, making it vital for fine motor skills and hand function.

Understanding the role of the median nerve in thumb movement underscores its significance in hand dexterity. Dysfunction or injury to the median nerve can lead to weakness or paralysis of the APB, resulting in compromised ability to abduct the thumb, which is crucial for many daily activities. This connection emphasizes the importance of the median nerve in upper extremity function, particularly related to the thumb's complex motions.