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The shoulder joint, also known as the glenohumeral joint, is a ball and socket joint with the most extensive range of motion in the human body. The shoulder muscles have a wide range of functions, including abduction, adduction, flexion, extension, internal and external rotation. The central bony structure of the shoulder is the scapula, where all of the muscles interact. At the lateral aspect of the scapula is the articular surface of the glenohumeral joint, the glenoid cavity. The glenoid cavity is peripherally surrounded and reinforced by the glenoid labrum, shoulder joint capsule, supporting ligaments, and the myotendinous attachments of the rotator cuff muscles. The muscles of the shoulder play a critical role in providing stability to the shoulder joint. The primary muscle group that supports the shoulder joint is the rotator cuff muscles. The four rotator cuff muscles include the supraspinatus, infraspinatus, teres minor, and subscapularis. Other muscles that form the shoulder girdle include the pectoralis major, pectoralis minor, the deltoids, trapezius, and the serratus anterior.

The upper limb comprises many muscles which are organized into anatomical compartments. These muscles act on the various joints of the hand, arm, and shoulder, maintaining tone, providing stability and allowing precise fluid movement.

Muscles Of Upper Limb Pdf Download

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Axioappendicular groups of muscles arise from the axial skeleton to act upon the pectoral girdle. Scapulohumeral muscles originate from the scapula and insert into the proximal humerus. Included in this category are the rotator cuff muscles which provide stability to the glenohumeral joint. In the arm, the muscles of the anterior compartment are involved in flexion of the forearm, and the posterior comprises of the forearm extensors. Similarly, the anterior compartment of the forearm contains the flexors of the hand and posterior has extensors. The hand is divided into the thenar, the hypothenar, the adductor compartment, as well as the short muscles of the hand.[1][2][3][4]

Shoulder and Upper limb muscles are specialized to perform functions of pressure and manipulation of objects. Skeletal muscle is formed by myofibers which contain millions of myofibrils, and each of them is formed by sarcomeres. Sarcomeres are the contractile unit, therefore skeletal muscle fibers are completely dedicated to generating force. Skeletal muscle also carries out multiple functions such as voluntary locomotion, the protection of internal organs, generation of heat, and assisting in postural behavior. [5][6]

Mesenchyme (mesodermal in origin) condenses into sets of dermatomes and myotome complexes. Myotomes migrate into the developing limb buds, to give rise to myoblasts. Elongation of the limb buds, along with muscle formation from myoblasts, compartmentalizes the muscles into their respective muscle groups.

The arterial supply to the muscles of the upper limb is primarily from the axillary artery (of subclavian artery) and its branches. The brachial artery supplies to the anterior compartment of the arm, and the profunda brachii supplies the posterior. In the arm, the radial artery supplies the lateral forearm and the ulnar is responsible for the medial aspect. Beyond the wrist, the radial and ulnar arteries form the superficial and deep palmar arterial arches. The deoxygenated blood drains into the cephalic vein and the basilic vein. Lymphatics of the right upper limb drain into the right lymphatic duct, and the left drains into the thoracic duct.[4][8][9]

The biceps brachii is one of the most variable muscles in the human body, this muscle can have more than two heads arising from humerus at the insertion of the coracobrachialis or neck of the humerus. Some reports describe supernumerary bicipital heads fluctuating from 3 to 7 in different groups, being the 3 heads variant the most common type.

Upper extremity injuries are usually treated in non-operative modalities such as medications, splints, injection, physical therapy. The surgical consideration of the muscles of the upper limb depends on the underlying condition.

The surgical purpose in upper limb dysfunction due to brain injury is to decrease muscle spasticity, correct joint contractures, as well as enhance the appearance, and function of the extremity. Some of the approaches to increase or decrease the muscle tone imply the peripheral nerve surgery or lengthening hyperactive muscles.

Some injuries where fractures and destruction of soft tissues (skin and muscles) are present, a multidisciplinary approach is required in which the orthopedic surgeons work with plastic surgeons to treat open fractures of the extremities, osteomyelitis, or unstable scars correctly.

This is the congenital ipsilateral absence or hypoplasia of pectoralis major and pectoralis minor muscles with hypoplasia of the corresponding ribs. It is hypothesized to be caused by an in-utero defect of blood supply to the developing chest. Poland syndrome is commonly associated with defects in breast and/or upper limb development.

Lateral epicondylitis (tennis elbow) is caused by a combination of repetitive or sustained contraction of the extensor muscles of the forearm leading to inflammation of the common extensor origin. Medial epicondylitis (golfers elbow) is due to repetitive or sustained contraction of the flexor muscles of the forearm leading to inflammation of the common flexor origin. Patients present with pain and tenderness over the affected epicondyle that worsens with extension (in the case of lateral epicondylitis) or flexion (when suspecting medial epicondylitis). Treatment involves avoiding exacerbating activities, physical therapy, and pain relief.

Traumatic injury, malignancy, infection, or congenital deformity of the upper extremity can lead to amputation. Surgeons have different surgical options to improve the potential of using prosthetic technologies for this group of patients. Targeted muscle reinnervation is a surgical procedure to enhance the control of myoelectric upper limb prostheses, and it helps to prevent and treat painful postamputation neuromas. This technique was originally described for transhumeral amputations and shoulder disarticulations but nowadays it has also been applied in the treatment of transtibial, transfemoral, transradial, and partial hand amputees. [15][16]

There are 4 muscles of the pectoral region: pectoralis major, pectoralis minor, serratus anterior and subclavius. Collectively, these muscles are involved in movement and stabilisation of the scapula, as well as movements of the upper limb.

The muscles of the shoulder joint can be divided into an intrinsic and extrinsic group; The extrinsic group originate from the torso and attach to the bones of the shoulder, whereas the intrinsic ones originate from the bones of the shoulder and attach the humerus. They collectively act to move the upper arm and stabilise the shoulder joint.

The upper arm, located between the shoulder and elbow joint, has an anterior and posterior compartment. The muscles located in the anterior compartment are involved in flexion at the elbow and shoulder joint whereas muscle in the posterior compartment, triceps brachii, extends the arm at the elbow joint.

The muscles of the forearm are subdivided into an anterior and posterior compartment. The muscles of the anterior compartment are further divided into a superficial, intermediate and deep layer; Innervated by both the ulnar and median nerve, they collectively act to pronate the forearm and to flex the wrist and the digits.

The muscles of the posterior compartment are separated into a superficial and deep layer. These muscles are innervated by the radial nerve and are known as the extensor muscles due to their general action of extending the wrist and the digits.

The muscles of the hand can be divided into an extrinsic and intrinsic group. The extrinsic group originate from the forearm and attach to the bones of the hand, they are associated with forceful or non-precise movements. On the other hand, the intrinsic group originate and attach within the hand itself and are more involved with fine-tuned and delicate movements. Both groups are innervated by the ulnar and median nerve.

The muscles of the upper extremity include those that attach the scapula to the thorax and generally move the scapula, those that attach the humerus to the scapula and generally move the arm, and those that are located in the arm or forearm that move the forearm, wrist, and hand. The illustration below shows some of the muscles of the upper extremity.

The muscles that move the forearm are located along the humerus, which include the triceps brachii, biceps brachii, brachialis, and brachioradialis. The 20 or more muscles that cause most wrist, hand, and finger movements are located along the forearm.

By looking at all of the upper limbs components separately we can appreciate and compartmentalize the information, then later view the upper limb as a whole and understand how all of its parts work in unison. 006ab0faaa