The shoulder Flashcards
what does the region of the shoulder include
The pectoral, scapular, and lateral supraclavicular regions
what is the pectoral girdle made out of
- the calvicle and the scapula
what does the humorous articular with
- Humorous articulates with the scapula so that the shoulder regions is connected to the pectoral girdle
what is the pectoral girdle
- Pectoral (shoulder) girdle is a bony ring, it is a moveable and flexible region
describe the structure of the pectoral girdle
- Incomplete posteriorly because the scapula doesn’t articulate bone to bone with the vertebral column, it is attached by muscles to the vertebral column
- scapula acts as a muscle attachement points
- Formed by the scapulae (posteriorly) and clavicles (anteriorly)
- Completed anteriorly by the manubrium of the sternum
- clavicle overlies the first rib
where does the clavicle articular with the sternum
- articulates anteriorly and forms the sternoclavicular joint
why can you palpitate along the clavicle
- because no muscles cross it anteriorly
what causes protractor and retraction in the pectoral girdle
the muscle attached between the scapula and vertebral column
describe the structure of the scapula
- Clavicle (collar bone) connects the upper limb to the manubrium via sternoclavicular joint
- acromioclavicular joint, articulation with acromion of scapula and the clavicle
- the acromioclavicular joint keeps arm away from thorax, giving maximum freedom of movement
- s curve that acts as a spring in the clavicle – this means that it can be more flexible and absorb shock
what does the S shape curve in the clavicle do
- it increases its resilience
how are fractures caused in the clavicle
- direct or indirect force
describe what the fracture looks like
-medial part points upwards whereas lateral part points onwards creating a tent of the skin
this happens because..
– The Weight of arm drags lateral fragment inferiorly.
– And the Action of sternocleidomastoid pulls medial fragment superiorly
describe the promotion of breakages that are clavicles
– 2-5% of adult fractures
– Most frequently fractured bone n childhood – sometimes happens during birth
what does the clavicle protect
Brachial plexus
Major underlying vessels
Apex of lung
what is the scapula
Triangular flat bone on posterolateral aspect of thorax,
what ribs does the scapula overlie
2nd to 7th rib
- this is the physiological scapulothroacic joint
what is the scapula an attachment site for
Attachment site for many shoulder/pectoral girdle muscles
describe the structure of the scapula
spine’ ridge on posterior side separates supraspinous fossa and infraspinous fossa
- Lateral end of spine of scapula - acromion,
what are the muscles that act on the scapula
- trapizieous acts on the scapula
- Trapizieus acts on the scapula
- Levator scapulae – lifts the scapula – it attaches to the top and lifts it
- Triceps brachii – one head attaches to the scapula
what is the humorous
- it is the largest bone in the body
what does the humorous articular with
- Articulates with scapula at glenohumeral joint and radius and ulna at elbow joint
describe the sternoclavicular joint
- Clavicle and manubrium of the sternum and 1st costal cartilage
- Strength due to strong ligaments
- Only articulation between upper limb and axial skeleton
what does the interarticular disc do int he sternoclavicular joint
– fibrocartilage that fits into the joint – this acts as packing and a shock absorber – make certain that the joint surfaces are closer together to prevent movement
describe the structure of the acromioclavicular joint
– Between Acromion and clavicle
– located 2-3 cm from ‘point of the shoulder’
– No muscles cross AC joint
– Muscles moving scapula move AC joint – when the scapula moves the AC joint moves
what is stronger the sternoclavicular joint or the acromioclavicualr joint
– Not as strong as sternoclavicular, interarticular disc is not as large as the one in the sternoclavicular joint
describe how the acromioclavicular can dislocate
– the clavicle is intact but just separated, the clavicle moves up due to the sternocleimastoid, and gravity moves the shoulder and the scapula down
what muscles cause ... movement in the scapula 1. elevation 2 depression 3 protection 4 retraction 5 upward rotation 6 downward rotation
Elevation - Trapezius (descending) Depression - Gravity Protraction - Serratus anterior - Pectoralis minor Retraction - Trapezius (middle) Upward rotation - Trapezius (descending) - Serratus anterior (inferior) Downward rotation - Latissimus dorsi
what does the glenoid cavity articular with
head to the humorous
describe the structure of the glenoid cavity
– Shallow glenoid cavity deepened by ring of fibrocartilage - ‘glenoid labrum – it helps to hold the head of the humerous against the shallow depression of the glenoid cavity’ – it is a slight depression in the glenoid region in the scapula, the head of the humerous is about 4 times bigger then the glenoid cavity
– Fibrous joint capsule loose and baggy – increases the range of movement
why is there a large freedom of movement in the glenohumeral joint
– Due to loose articular capsule,
– large humeral head compared to shallow/small glenoid cavity – this prevents any bone restrictions that limit the head of the humorous from moving
what movements can the glenohumeral joint do
– flexion-extension
– abduction-adduction
– medial and lateral rotation
– circumduction (combination flexion, extension, abduction and adduction)
what are the chief flexors in the glenohumeral joint
Chief flexors
Pectoralis major (clavicular part)
Deltoid (anterior part) - comes from the clavicle, goes round the arcomin onto the scapula spine
- Coracobrachialis assisted by biceps brachii which stabilises the joint
what are the chief extensors in the glenohumeral joint
Chief extensors
Latissimus dorsi - attaches to the humerous and the vertebrae
Deltoid (posterior fibres)
- Teres major - Long head of triceps brachii helps stabilise the joint
what are the chief abductors in the glenohumeral joint
chief abductor
Deltoid (all parts but especially central fibres)
Solely active 110-180o of abduction
Supraspinatus does 1st 10o of abduction
Active and works with deltoid 10- 110o of abduction
describe how the physiological scapulotheraicic joint works
- the head of the humerus uses all the available articular space when it moves to 90 degrees, the supraspinatus and deltoid help it do this abduction
- up to 30 degrees the scapula is in a position of stability
- beyond 30 degrees scapula rotates upwards to reposition glenoid fossa - serratus anterior and trapezius help it do this
- there is a 2:1 ratio over the 180 degree of shoulder abduction, 120 degrees occurs at the glenohumeral joint and 60 degrees occurs at the scapualthroacic joint
what is the 2:1 ratio of shoulder abduction
- there is a 2:1 ratio over the 180 degree of shoulder abduction, 120 degrees occurs at the glenohumeral joint and 60 degrees occurs at the scapualthroacic joint
what are the chief adductors
Pectoralis major
Latissimus dorsi
Gravity is prime mover
what is the chief medial rotator
Subscapularis
what is the chief lateral rotator
Infraspinatus
what are rotator cuff muscles
- Group of 4 muscles that surround the scapula and attach to the head of the humerous
what are movements that are combined often
- abduction and external rotation
- adduction and internal rotation
what are the 4 muscles that stabilise the glenohumeral joint
- Supraspinatus – abductor - goes to the greater tuberosity
- Infraspinatus- goes into the greater tuberisocity
- Teres minor – goes into the greater tuberiosicty
- Subscapularis – goes into the lesser tuberosicty
what do the glenohumeral joints do
- Form musculotendinous cuff around glenohumeral joint blending with articular capsule
- Tonic contraction holds relatively large humeral head in shallow glenoid cavity
where do glenohumeral joints attach
- 3 attach to greater tuberosity of humerus
- 1 attaches to lesser tuberosity of humerus
what are bursae
- Protect tendons
- Bursae act as cushions and reduce friction in order to protect tendons
- they are normally filed with fluid
where is the bursae
- They are underneath the acromin and can protect the supraspinatus tendon
what causes pain on abduction of the arm
- Subacromial bursa inflammation (bursitis) causes pain on abduction of arm
what is the most common glenohumeral joint dislocation
- anterior dislocation
why when you dislocate the glenohumeral joint is it weaker
Glenoid labrum may be stripped from anterior aspect of glenoid cavity, making joint weaker
how does dislocation of the glenohumeral joint dislocate
- Glenohumeral joint fully abducted tilts head of humerus inferiorly onto weaker part of joint
- Strong flexor and adductor muscles pull humeral head anteriorly
- this causes the humerus to go into the weaker part of the join where there is not muscle there
- the rounded profile of the shoulder is lost and gravity pulls the humorous inferiorly
what is the problem with a glenohumeral dislocation
Axillary nerve can be compressed or damaged completely as it is near the inferior part of the glenohueral joint
what are the consequences of the axillary nerve being damaged
– Deltoid
• Impaired abduction – can no longer do abduction
– Loss of sensation over “regimental badge
– Long term dmage is that the deltoid atrophies and waste end up with a really weak shoulder
what does the axillary nerve innervate
the deltoid muscle
