Week 8 - Glenohumeral Joint Flashcards
What is the glenohumeral joint?
A ball and socket joint type of synovial joint that permits a wide range of movement; however, its mobility makes the joint relatively unstable
Where does the humeral head articulate
With the relatively shallow glenoid cavity of the scapula
How is the glenoid cavity deepened?
It is deepened slightly but effectively by the ring like, fibrocartilaginous glenoid labrum
What are both the articular surfaces covered with?
Hyaline cartilage
How much of the humeral head does the glenoid cavity accept?
Little more than a third
How is the humeral head held in the glenoid cavity?
By the tonus of the musculotendinous rotator cuff, or SITS, muscles
What surrounds the glenohumeral joint?
Loose fibrous layer of the joint capsule
How is the loose fibrous layer of the joint capsule attached?
Medially to the margin of the glenoid cavity and laterally to the anatomical neck of the humerus
What does the fibrous layer of the capsule enclose?
The proximal attachment of the long head of the biceps brachii to the supra-glenoid tubercle of scapula withing the joint
What are the two apertures of the joint capsule?
An opening between the tubercles of the humerus
An opening situated anteriorly, inferior to the coracoid process
What is the opening between the tubercles of the humerus for?
FOr passage of the tendon of the long head of the biceps brachii
What is the opening situated anteriorly, inferior to the coracoid process for?
It allows communication between the subtendinous bursa of subscapularis and the synovial cavity of the joint
What is the only part of the joint capsule not reinforced by the rotator cuff muscles?
The inferior part, which is the weakest part
What happens to the joint capsule at the inferior part when the arm is adducted?
It lies in folds
What happens to the joint capsule at the inferior part when the arm is abducted?
It becomes taught
What does the synovial membrane do?
Lines the internal surface of the fibrous layer of the capsule and reflects from it into the glenoid labrum and the humerus, as far as the articular margin of the head
What does the synovial membrane form?
A tubular sheath for the tendon of the long head of the biceps brachii, where it lies in the intertubercular sulcus of the humerus and passes into the joint cavity
What does the glenohumeral ligament strengthen?
The anterior aspect of the joint capsule
What does the coracohumeral ligament strengthen?
The joint capsule superiorly
What are the glenohumeral and the coracohumeral ligaments?
Intinsic ligaments - that is, part of the fibrous layer of the joint capsule
How many fibrous bands are the glenohumeral ligaments?
Three
Where are the glenohumeral ligaments evident?
On the internal aspect of the capsule
Where do the glenohumeral ligaments radiate?
Laterally and inferiorly from the glenoid labrum at the supraglenoid tubercle of the scapula
Where do the glenohumeral ligaments blend?
With the fibrous layer of the capsule as it attaches to the anatomical neck of the humerous
What is the coracohumeral ligament?
A strong broad band that passes from the base of the coracoid process to the anterior aspect of the greater tubercle of the humerus
What is the transverse humeral ligament?
A broad fibrous band that runs more or less obliquely from the greater to the lesser tubercle of the humerus, bridging over the intertubercular sulcus
What does the transverse humeral ligament convert the groove into?
A canal which holds the synovial sheath and tendon of the biceps brachii in place during movements of the glenohumeral joint
What is the coraco-acromial arch?
An extrinsic, protective structure formed by the smooth inferior aspect of the acromion and the coracoid process of the scapula, with the coraco-acromial ligamnet spanning between them
What does the coraco-acromial arch prevent?
The superior displacement of the humeral head from the glenoid cavity
How is movement of the supraspinatus tendon, passing to the greater tubercle of the humerous facilitated?
As it passes under the arch by the subacromial bursa, which lies between the arch supeiorly and the tendon of the tubercle inferiorly
What is the freedom of movement of the glenohumeral joint the result of?
The laxity of its joint capsule and the large size of the humeral head compared with the small size of the glenoid cavity
Around how many axes does the humeral joint allow movements?
Three
What movements of the humerus and circumduction does the glenohumeral joint allow?
Flexion - extension
Abduction - adduction
Rotation (medial and lateral)
What does lateral rotation of the humerus increase?
The range of abduction
What happens when the arm is abducted without rotation?
Available articular surface is exhausted and the greater tubercle contacts the coraco-acromial arch, preventing further abduction
What is circumduction at the glenohumeral joint?
An orderly sequence of flexion, abduction, extension and adduction - or the reverse
If there is stiffening or fixation of joints of the pectoral girdle what can happen?
There is a much more restricted range of movements , even if the glenohumeral joint is normal.
Where do the axio-appendicular muscles act?
Indirectly on the glenohumeral joint
Where do the scapulohumeral muscles act?
Directly on the glenohumeral joint
What is the glenohumeral joint supplied by?
The anterior and posterior circumflex humeral arteries and branches of the supra-scapular artery
What nerves supply the glenohumeral joint?
Suprascapular nerve
Axillary nerve
Lateral pectoral nerve
What is a bursae?
A sac-like cavity
What do bursae contain?
Capillary films of synovial fluid secreted by the synovial membrane
Where are bursae located?
Where tendons rub against bone, ligaments or other tendons and where skin moves over a bony prominence
Why are the bursae around the glenohumeral joint of special clinical importance?
Because some of them communicate with the joint cavity
Where is the subtendinous bursa of the subscapularis located?
Between the tendon of the subscapularis and the neck of the scapula
What does the subtendinous bursa of the subscapularis protect?
The tendon where it passes inferior to the root of the coracoid process and over the neck of the scapula
Where is the subacromial bursa located?
Between the acromion , coraco-acromial ligamen, and deltoid superiorly and the supraspinatus tendon and joint capsule of the the glenohumeral joint inferiorly
