The muscles of the upper limb can be divided into six regions, which include the pectoral, shoulder, upper arm, anterior forearm, posterior forearm, and the hand. Each of these regions plays a vital role in the movement and stability of the upper limb, as well as providing support for various functions of the arm.
The pectoral region is located on the front of the torso and consists of four muscles: pectoralis major, pectoralis minor, serratus anterior, and subclavius. They work together to provide movement and stability to the scapula, as well as aiding in the movement of the upper limb.
The muscles of the shoulder joint can be divided into extrinsic and intrinsic groups. The extrinsic group originates from the torso and attaches to the bones of the shoulder, while the intrinsic group originates from the bone of the shoulder and attaches to the humerus. Together, these muscles help to move the upper arm and stabilize the shoulder joint.
The upper arm lies between the shoulder and elbow joints and carries out a variety of functions. It has both an anterior and posterior compartment, with the muscles in the anterior compartment responsible for flexing the elbow and shoulder joint, while the muscle in the posterior compartment, triceps brachii, is responsible for extending the arm at the elbow joint.
The muscles of the forearm are separated into an anterior and posterior compartment. The anterior compartment is further divided into superficial, intermediate, and deep layers; these muscles are innervated by both the ulnar and median nerve, and they work together to pronate the forearm and flex the wrist and the digits. The posterior compartment is also divided into superficial and deep layers and is innervated by the radial nerve. These muscles are known as the extensor muscles and are responsible for extending the wrist and digits.
The muscles of the hand can be divided into an extrinsic and intrinsic group. The extrinsic group originates from the forearm and attaches to the bones of the hand, and these muscles are typically associated with forceful or unpolished movements. The intrinsic group originates and attaches within the hand itself and is involved in movements that require finer control.
Both the extrinsic and intrinsic group of muscles are innervated by the ulnar and median nerve, which allows one to perform a variety of movements with the hand. Through the complex interaction of these muscles, one is able to make use of their upper limbs for a variety of purposes, whether it is for carrying out a daily activity or for a more specific purpose.
