the shoulder joint

Question 1

shoulder joint (glenohumeraljoint)

Answer 1

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

Question 2

articulating surface of the humeral head

Answer 2

much larger than that of the glenoidf ossa to allow for range of motion

Question 3

movements of the shoulder joint

Answer 3

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

Question 4

glenoid fossa (cavity)

Answer 4

deepended by a lip of cartilage, the glenoid labrum

Question 5

coracoacromial ligament

Answer 5

links the caracoid and acromian processes; it lies above the head of the humerus, and helps to prevent displacement (dislocation) of the humeral head

Question 6

the joint capsule

Answer 6

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

Question 7

interlude

Answer 7

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

Question 8

extensions of the shoulder joint capsule form

Answer 8

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

Question 9

the tendon of the long head of biceps

Answer 9

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.

Question 10

how the tendon of the long head of the biceps is held in place

Answer 10

in the bicpital groove by the transverse humeral ligament

Question 11

coracoacromial ligament

Answer 11

helps to prevent upward displacement of the humeral head

Question 12

pectoralis major

Answer 12

most anterior muscle; attaches to the lateral lip of teh bicipital groove

Question 13

latissimus dorsi and teres major

Answer 13

posterior muscles; attach to the floor and medial lip of the bicipital groove, respectively.

Question 14

teres major

Answer 14

attaches to the scapula, “behind” the chest wall, and therefore lies medial to (posterior to) latissimus dorsi on the humerus

Question 15

acromioclavicular joint

Answer 15

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

Question 16

dislocation of the acromioclavicular joint

Answer 16

“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

Question 17

anastomosis of blood vessels in the shoulder joint

Answer 17

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

Question 18

muscles acting on the shoulder joint

Answer 18

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

Question 19

supraspinatus

Answer 19

an abductor (it lies above the shoulder joint)

Question 20

infaspinatus and teres minor

Answer 20

lateral rotators (their tendons lie posterior to the joint)

Question 21

muscle on the deep surface of the scapula (when viewed from behind)

Answer 21

subscapularis; its tendon passes anterior to the shoulder joint, so it is a medial rotator

Question 22

subscapular bursa

Answer 22

protects the tendon

Question 23

supraspinatus and infraspinatus

Answer 23

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

Question 24

tendon of the supraspinatus

Answer 24

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

Question 25

inflammation of the subacromial bursa

Answer 25

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

Question 26

long head of the tricpes

Answer 26

passes between the teres minor and teres major, creating the quadrangularand two triangular spaces

Question 27

quadrangular space

Answer 27

allows passage of the axillary nerve and the posterior circumflex humeral artery

Question 28

the triangular interval

Answer 28

between the long head of triceps and the humerus allows passage of the radial nerve and profunda brachii artery

Question 29

triangular space between the teres muscle

Answer 29

allows passageof the circumflex scapular artery

Question 30

pectoralis major

Answer 30

an adductor and medial rotator

Question 31

tere major and latissimus dorsi

Answer 31

adductors

Question 32

biceps

Answer 32

a flexor

Question 33

triceps

Answer 33

an extensor via its long head

Question 34

deltoid

Answer 34

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;

Question 35

anterior fibers of the deltoid

Answer 35

flex the arm

Question 36

middle fibers of the deltoid

Answer 36

will adduct the arm

Question 37

posterior fibers of the deltoid

Answer 37

will extend the arm at the shoulder joint

Question 38

for full abduction of the upper limb, and for pushing and punching

Answer 38

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

Question 39

damage to the long thoracic nerve

Answer 39

resultsin the scapular bulging outward (“winged scapula) and weakness in abduction and pushing

Question 40

levator scapuli and the rhomboid muscles

Answer 40

assist the return to the scapula to its adducted position

Question 41

motion of the scapula

Answer 41

is transmitted via the acromioclavicular joint to the clavicle

Question 42

the sternoclaviucular joint

Answer 42

allows the required motions of the clavicle, hinging and rotation

Question 43

Hilton’s Law

Answer 43

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

Question 44

force of a fall on the outstretched hand (FOOSH)

Answer 44

is transmitted via the shoulder and acromioclavicular joints to the clavicle, and may fracture the clavicle (usually in its middle third)

Question 45

most dislocations of the shoulder

Answer 45

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