shoulder joint Flashcards
what muscles abduct the arm at the shoulder joint?
suprsaspinatus
deltoid
what is the action of supraspinous in relation to abducting the arm at the shoulder joint?
- initiates abduction being more important in the early stages
- Role is twofold during this movement, it braces the head of the humerus firmly against the glenoid fossa to prevent upward shearing of the humeral head, while at the same time producing abduction
- after the initial 20’ of abduction, when the stronger deltoid takes over, supraspinatus acts to hold the humeral head against the glenoid fossa
what is the action of deltoid in relation to abducting the arm at the shoulder joint?
- principle abductor
- movement is produced by its middle fibres
- can only produce this movement efficiently after it has been initiated by supraspinatus
- anterior part of deltoid is a strong flexor and medial rotator of the humerus
- posterior part is a strong extensor and lateral rotator and also active during adduction of the arm, to counteract the medial rotation produced by pectoralis major and latissimus dorsi
how is the upward shearing of the head of the humerus caused by deltoid resisted?
By the rotator cuff muscles, that is by subscapularis anteriorly, teres major and infrapspinous posteriorly and suprapsinatus superiorly
what is the functional activity of the deltoid muscle in relation to abducting the arm at the shoulder joint?
- active in abduction when the middle fibres contact concentrically, but the massive development and multipennate nature of the muscle are probably due to the fact that many activities of the upper limb require that it is maintained or ‘held’ in this long position for long periods of time
- middle fibres contact statically when performing activities with the arms in front of the trunk they then lower the arm back to the side by working eccentrically
Muscles which flex the arm at the shoulder joint?
- pectoralis major
- deltoid (ant)
- biceps brachii (long head)
- coracobrachialis
action of pectoralis major in relation to flexing the arm at the shoulder joint?
- very powerful adductor and medial rotator of the humerus at the shoulder joint
- the clavicular part can flex the humerus to the horizontal, while the sternocostal fibre, because of their direction, can extend the flexed humerus, particularly against resistance in the anatomical position
- while the humerus is fixed as in gripping a table or chair back, pectoralis major pulls on the upper ribs to assist inspiration during respiratory distress
how does pectoralis major assist in functional activity in relation to flexing the arm at the shoulder joint?
- if the arms are fixed above the head, the power of the muscle can be used to pull the trunk upwards
- assisted in this activity by latissimus dorsi
- in pushing, punching and throwing, pectoralis major acts to move the humerus forcefully forwards while serratus anterior and pectoralis minor simultaneously protract the pectoral girdle
- press-ups, this muscle contracts concentrically on the upward movement raising the body eccentrically on the downward movement when lowering the body
what activity does pectoralis major assist in?
climbing
muscles extending the arm at the shoulder joint?
- latissimus dorsi
- teres major
- pectoralis major
- deltoid (post)
- triceps (long head)
what is the action of latissimus dorsi in relation to extending the arm at the shoulder joint?
- strong extensor
- if the humerus is fixed relative to the scapula it retracts the pectoral girdle
- it is also a strong adductor and medial rotator of the humerus at the shoulder joint
What is the functional activity of latissimus dorsi in relation to extending the arm at the shoulder joint?
- a climbing muscles, and with the arms fixed above the head it can raise the trunk upwards
- important in rowing and the downstroke in swimming
- active in violent expiration
- attachment to the inferior angle of the scapula can allow it to assist in holding it against the thorax during movements of the upper limb
what is the action of teres major in relation to extending the arm at the shoulder joint?
- adducts and medially rotates the humerus at the shoulder joint
- it can help extend the flexed arm
what is the functional activity of teres major in relation to extending the arm at the shoulder joint?
- climbing muscle and works with the latter and pectoralis major to pull the trunk upwards when the arms are fixed
- in conjunction with latissimus dorsi and pectoralis major, it is important in stabilising the shoulder joint
muscles adducting the arm at the shoulder joint?
- coracobrachialis
- pectoralis major
- latissimus dorsi
- teres major
