the shoulder joint Flashcards
shoulder joint (glenohumeraljoint)
ball-and-socket joint betweenthe glenoid fossa of the scapula and the head of the humerus; it is specialized for grater range of motion rather than maximum stability
articulating surface of the humeral head
much larger than that of the glenoidf ossa to allow for range of motion
movements of the shoulder joint
abduction/adduction, flexion/extension, and their comnbination circumduction
gliding in the joint allows rotation of the humeral shaft for lateral/medial (or internal/external) rotation of the arm; these last are best seen when the elbow is flexed
glenoid fossa (cavity)
deepended by a lip of cartilage, the glenoid labrum
coracoacromial ligament
links the caracoid and acromian processes; it lies above the head of the humerus, and helps to prevent displacement (dislocation) of the humeral head
the joint capsule
is strong but thin and loose, particularly inferiorly, to allow range of motion. the capsule is strengthened anteriorly by the glenohymeral ligament and superiorly by the caracohumeralligament attached to the caracoid process
interlude
a synovial joint cavity, a bursa and a tendon sheath are all cavities bounded by a synovial membrane filled with synovial fluid. bursae and tendon sheats are interposed between a bone and a muscle, and a bone and a tendon, respectively. two layers of the synovial sac slide against each other and are lubricated by synovial fluid, allowing easy movement
extensions of the shoulder joint capsule form
1) the subscapular bursa, separating a portion of subscapularis from the scapula
2) a synovial sheath for the biceps tendon
like the shoulder joint, these structures are spaces surrounded by synovial membrane and containing a synovial fluid; the spaces are continuous with each other, allowing spread of infection
the tendon of the long head of biceps
passes within the joint capsule to attach to the superior glenoid tubercle, as shown in this cross-section. Note how this biceps tendon pulls the head of the humerus into the glenoid fossa as it contracts. this stabilizes the shoulder. synovial space within the tendon sheath is continuous with the joint space of the shoulder joint.
how the tendon of the long head of the biceps is held in place
in the bicpital groove by the transverse humeral ligament
coracoacromial ligament
helps to prevent upward displacement of the humeral head
pectoralis major
most anterior muscle; attaches to the lateral lip of teh bicipital groove
latissimus dorsi and teres major
posterior muscles; attach to the floor and medial lip of the bicipital groove, respectively.
teres major
attaches to the scapula, “behind” the chest wall, and therefore lies medial to (posterior to) latissimus dorsi on the humerus
acromioclavicular joint
transmits movement of the scapula to the clavicle; this is a synovial plane joint, strengthened by the acromioclavicular and, especially, by the caracoclavicular ligament, composed in turn of the trapezoid and conoid ligaments, named for their shape
dislocation of the acromioclavicular joint
“shoulder separation;” this is not separation fo teh glenohumeral (shoulder) jointitself; more serious separations of the joint can involve tearing of the supporting ligaments, the weather acromioclavicular ligament and the stronger caracoclavicular ligament
anastomosis of blood vessels in the shoulder joint
arising primarily from the axillary artery that crosses the joint; arteries include the acromial branch of the thoracoacromial artery, arising proximal to the joint, and the anterior and posterior circumflex humeral arteries that arise distal to the joint
muscles acting on the shoulder joint
primary stabilizersof the joint: rotator cuff muscles
on the posterior side, attaching in order, from superior to inferior, on the greater tuberosity of the humerus are: supraspinatus, infraspinatus, and teres minor
supraspinatus
an abductor (it lies above the shoulder joint)
infaspinatus and teres minor
lateral rotators (their tendons lie posterior to the joint)
muscle on the deep surface of the scapula (when viewed from behind)
subscapularis; its tendon passes anterior to the shoulder joint, so it is a medial rotator
subscapular bursa
protects the tendon
supraspinatus and infraspinatus
lie on the superior surface of the scapular and are supplied by branches of the suprascapular nerve and artery; the nerve (but not the artery) passes beneath the transverse scapular ligament (also called the suprascapular or superior transverse ligament) where is may be trapped
tendon of the supraspinatus
separates the subacromial bursa from the shoulder joint cavity and the two synovial spaces are not normally continuos with each other; a portion of the subacromial bursa lies deep to the deltoid muscle
inflammation of the subacromial bursa
bursitis; it causes pain and difficulty with abduction; damage to the bursa may also allow the supraspinatus tendon to rub against the acromian and thereby damage the tendon, eventually allowing communication between the subacromial bursa and the shoulder joint cavity
long head of the tricpes
passes between the teres minor and teres major, creating the quadrangularand two triangular spaces
quadrangular space
allows passage of the axillary nerve and the posterior circumflex humeral artery
the triangular interval
between the long head of triceps and the humerus allows passage of the radial nerve and profunda brachii artery
triangular space between the teres muscle
allows passageof the circumflex scapular artery
pectoralis major
an adductor and medial rotator
tere major and latissimus dorsi
adductors
biceps
a flexor
triceps
an extensor via its long head
deltoid
an abductor, flexor, and extensor; this muscle is attached to the spine of the scapula, the acromion and the lateral third of the clavicle;it inserts on the deltoid tuberosity of the humerus;
anterior fibers of the deltoid
flex the arm
middle fibers of the deltoid
will adduct the arm
posterior fibers of the deltoid
will extend the arm at the shoulder joint
for full abduction of the upper limb, and for pushing and punching
the scapula must rotate more anteriorly on the chest wall; this action is performedby the trapezius and serratus anterior muscles, supplied by the spinal accessory and long thoracic nerves; the serratus anterior muscle also holds the scapula close to the chest wall
damage to the long thoracic nerve
resultsin the scapular bulging outward (“winged scapula) and weakness in abduction and pushing
levator scapuli and the rhomboid muscles
assist the return to the scapula to its adducted position
motion of the scapula
is transmitted via the acromioclavicular joint to the clavicle
the sternoclaviucular joint
allows the required motions of the clavicle, hinging and rotation
Hilton’s Law
nerves supplying a joint are branches of nerves supplying muscles that act on the joint; thus nerves that supply the shoulder joint are branches of the suprascapular, axillary, and lateral pectoral nerves; these nerves also innervate the muscles that move the joint
force of a fall on the outstretched hand (FOOSH)
is transmitted via the shoulder and acromioclavicular joints to the clavicle, and may fracture the clavicle (usually in its middle third)
most dislocations of the shoulder
occur anteriorly, due to forcible extension while the shoulder is abducted; dislocation may stretch the axillary nerve and damage it, causing wasting of the deltoid muscle and loss of its function
