The shoulder region and muscles of the scapula and posterior arm Flashcards
which muscles are responsible for abduction of the shoulder?
Initiation is supraspinatus and then it is assisted by deltoid. Rotation of the scapula is by trapezius.
Describe the movements of the scapula and humerus during abduction of the shoulder.
Supraspinatus initiates abduction and after 10-15 degrees it is assisted by deltoid. As the arm rises the humerus externally rotates to keep the articular surfaces in contact. At full abduction (upper limb vertically above the head) the humerus has externally rotated 90 degrees. For every 2 degrees of abduction at the glenohumeral joint the scapula rotates by 1 degree over the thoracic wall. In full abduction (upper limb vertically above the head) the scapula is rotated so that the glenoid points upwards by 60 degrees.
Which nerve supplies trapezius?
Spinal accessory nerve (cranial nerve XI)
Which nerve is damaged by a posterior dislocation of the shoulder and what sensory and motor loss is experienced?
Axillary nerve; sensory loss in skin over the insertion of deltoid muscle and paralysis of deltoid.
What structures stabilise the shoulder joint?
The rotator cuff muscles; supraspinatus,
infraspinatus, teres minor and subscapularis.
Which bony parts of the shoulder girdle lie subcutaneously and can be palpated easily?
Manubrium sternum, clavicle, spine of the scapula and acromium.
Will “Saturday night palsy” result in a weakness of triceps, explain your answer?
No. Saturday night palsy is loss of function of the radial nerve as it runs against the mid-shaft of the humerus in the spiral groove. Although the posterior compartment of the arm, which is formed by triceps, is supplied by the radial nerve the branches leave the nerve before the spiral groove.