Question

Highlight moments of the; Sternoclavicular joints, Acromioclavicular joints scapular and glenohumeral joint during movements of the shoulder and shoulder girdle. List out the key muscles involved, highlighting their origins and insertions as well as their contributions to the outlined movements. PLEASE GIVE REFERENCES of where you found the information ( website, book,..) Thank you :)

Answer 1

The Three Bones

The clavicle
The scapula
The proximal humerus form the shoulder with other muscles and ligaments

The Sternoclavicular Joint

Where the Clavicle articulates with the manubrium of the sternum

The Acromioclavicular joint

Where the Clavicle articulates with the acromion process

The Glenohumeral joint

Where the head of the humerus articulates with the glenoid fossa

Structures of the Shoulder Joint

Articulating Surfaces

The synovial joints, the articulating surfaces are covered with hyaline cartilage. The head of the humerus is larger than the glenoid fossa, and the joint showa a wide range of movement at the cost of inherent instability. The glenoid fossa theis deepened by a fibrocartilage rim, called the glenoid labrum.

Joint Capsule and Bursae

The joint capsule is a fibrous sheath

The capsule encloses the structures of the joint.

The joint capsule is lax, permitting greater mobility (particularly abduction).

To reduce friction in the shoulder joint, several synovial bursae are present. A bursa is a synovial fluid filled sac which acts as a cushion between tendons and other joint structures.

Movements

As a ball and socket synovial joint, a wide range of movement is permitted by the muscles

Extension (upper limb backwards in sagittal plane) – posterior deltoid, latissimus dorsi and teres major.

Flexion (upper limb forwards in sagittal plane) – pectoralis major, anterior deltoid and coracobrachialis. Biceps brachii weakly assists in forward flexion.

Abduction (upper limb away from midline in coronal plane):

abduction is produced by the supraspinatus.

The middle fibres of the deltoid are also involved.

The abduction with scapula – that is carried out by the trapezius and serratus anterior.

Adduction (upper limb towards midline in coronal plane) – pectoralis major, latissimus dorsi and teres major.

Internal rotation (rotation towards the midline, so that the thumb is pointing medially) – subscapularis, pectoralis major, latissimus dorsi, teres major and anterior deltoid.

External rotation (rotation away from the midline, so that the thumb is pointing laterally) – infraspinatus and teres minor.

Parts contributing to mobility:

Type of joint – ball and socket joint.

Bony surfaces – shallow glenoid cavity and large humeral head

Joint capsule.

bursae of shoulder joint

ligaments of shoulder joint

rotor cuff muscles of shoulder joint