Muscles of the posterior shoulder week 2

Question 1

How are origins and insertions defined?

Answer 1

origins: proximal attachment sites
insertions: distal attachment sites

Question 2

concentric contraction

Answer 2

muscle shortening that occurs when one attachment point of a muscle remains fixed while the other moves toward the fixed site. this usually results in movement at a joint that the muscle crosses

Question 3

eccentric contraction

Answer 3

occurs when a muscle is resisting being lengthened. a force, typically gravity along with some other load i.e. and external load or the weight of one’s own body, acts to draw the two attachment points of a muscle away from each other. the muscle undergoes a controlled relaxation and gradually lenghthens while continuing to exert a force. some examples are gradually lowering a hand weight after performing a bicep curl or performing the descending phase of a squat (quadriceps functions eccentrically to prevent knee from flexing too fast and bucking under the body’s weight)

Question 4

A balance btwn ____ and ___ muscle actions is necessary for coordinated activities such as walking, running, setting objects down, ascending and descending stairs, getting into and out of chairs, etc.

Answer 4

concentric and eccentric

Question 5

True or false: Rotator cuff muscles are essential for stability and mobility of the shoulder joint.

Answer 5

True.

Question 6

What are reasons for rotator cuff injuries?

Answer 6

Rotator cuff muscles are highly susceptible to injury and degenerative changes leading to shoulder pain and dysfucntion. Rotator cuff injuries include tears from trauma and impingments related to overuse but, additionally these muscles exhibit degenerative changes overtime due in part to aging, poor blood supply, and calcification of their tendons.

Question 7

What muscle is the most commonly injured muscle of the rotator cuff?

Answer 7

supraspinatus

Question 8

What are bursae? What is their function? What is bursitis?

Answer 8

bursae: small fluid filled sacs that intervene btwn tendons and surrounding bones to reduce friction and increase fluidity of motion at joints

bursitis: condition that involves inflammation of bursa

Question 9

Where is the subacromial bursa? What does bursitis of this bursa result in?

Answer 9

located btwn the supraspinatus tendon and the overlying acromion process of the scapula.

is susceptilbe to bursitis in overuse injuries to the shoulder. results in pain and decreased ability to use the affected arm

Question 10

Identify the bony landmarks of the posterior scapula.

Answer 10

Question 11

Identify the bony landmarks of the anterior scapula.

Answer 11

Question 12

Identify the bony landmarks of the humerus.

Answer 12

Question 13

Identify the ligaments of the shoulder complex.

Answer 13

Question 14

What muscles are part of the rotator cuff?

Answer 14

SItS

supraspinatus

infraspinatus

teres minor (reason for small t)

subscapularis

Question 15

Identify these muscles. What do these muscles comprise?

Answer 15

rotator cuff

Question 16

The ____ and ____ ____ are important muscles for movements of the upper limb but are NOT part of the rotator cuff!

Answer 16

deltoid and teres major

Question 17

What is the origin, insertion, function, and innervation of the deloid?

Answer 17

origin: lateral 1/3 of the clavicle, spine of the scapula, acromion process of the scapula
insertion: deltoid tuberosity of humerus

function:

anterior: flexion and medial rotates arm at glenohumeral joint
middle: abducts arm at glenohumeral joint
posterior: extension and lateral rotation of arm at glenohumeral joint
innervation: axillary nerve

Question 18

What are the origins, insertions, function, and innervation of the teres major?

Answer 18

origin: inferior angle of the scapula
insertion: medial lip of the intertubercular/bicipital groove of the humerus
function: adducts, medially rotates, and extends the arm at the glenohumeral joint
innervation: lower subscapular nerve

Question 19

What are the origins, insertions, function, and innervation of the supraspinatus?

Answer 19

origin: supraspinous fossa of scapula
insertion: greater tubercle of humerus
function: abducts arm at the glenohumeral joint (first 15 degrees. then deltoid takes over)
innervation: suprascapular nerve

Question 20

What are the origins, insertions, function, and innervation of the infraspinatus?

Answer 20

origin: infraspinous fossa of scapula
insertion: greater tubercle of humerus
function: laterally rotates arm at the glenohumeral joint
innervation: suprascapular nerve

Question 21

What are the origins, insertions, function, and innervation of the teres minor?

Answer 21

origin: upper 2/3 of the lateral border of the scapula
insertion: greater tubercle of humerus
function: laterally rotates arm at the glenohumera joint

innervation axillary nerve

Question 22

True or false: The infraspinatous and teres minor are a functional pair.

Answer 22

True. both fxn to laterally rotate the arm at the glenohumeral joint

Question 23

What are the origins, insertions, function, and innervation of the subscapularis?

Answer 23

origin: anterior surface of the scapula (subscapular fossa)
insertion: lesser tubercle of humerus
function: medially rotates the arm at the glenohumeral joint
innervation: upper/lower subscapular nerves

Question 24

Identify the muscles in this picture.

Answer 24

Question 25

What is the name of this muscle?

Answer 25

Question 26

The supraspinatus helps to hold the humerus in place and is essentially working all of the time to hold the arm up since most of the time, the arm is in a dependent position. What injury to the shoulder can arise if there is paralylsis of this muscle?

Answer 26

subluxation of the shoulder. head of humerus would fall down away from the glenoid fossa

Question 27

True or false: The infraspinatus, teres minor, and subscapularis together work to hold the humeral head agains the glenoid. They exert a downward glide on the head of the humerus which is necessary for abduction of the arm. Otherwise, the humeral head will compress structures superior to it into the acromion process (e.g. the supraspinatus tendon and subacromial bursa.

Answer 27

True.

Question 28

What two rotator cuff muscles laterally rotate the arm? Why is this important?

Answer 28

teres minor and infraspinatus. is important during abduction of the arm at the glenohumeral joint. cannot acheive full abduction without lateral rotation (try it!). this lateral rotation allows the greater tubercle of the humerus to clear the acromion process.

Question 29

Lateral or upward rotation of the scapula is caused in part by the _____ muscle, specifically the upper and lower fibers acting together. This is necessary because to abduct the arm fully overhead, we need about 180 degrees of motion. The glenohumeral joint gives us anywhere from 90-120 degrees of that motion, but the rest comes from the scapula upwardly rotating.

Answer 29

trapezius

Question 30

What creates the boundaries of the quadrangular space in the posterior shoulder? What nerve and artery emerges through this space? What does this nerve innervate? What muscles does the artery supply?

Answer 30

1. superior: teres minor
2. medial: long head of triceps brachii
3. inferior: teres major
4. lateral: surgical neck of the humerus

the posterior circumflex humeral artery and axillary nerve emerge from this space. (remember artery by posterior-posterior shoulder and humeral bc humerus is a border)

the axillary nerve innervates the teres minor and the deltoid

posterior circumflex humeral artery: supplies muscles in this region as well as the glenohumeral joint

Question 31

Where do the suprascapular artery and nerve emerge from? What does the suprascapular nerve innervate? What does the suprascapular artery supply blood to?

Answer 31

1. associated with the suprascapular notch of the scapula and its ligament, the superior transverse scapular ligament (calcified, sort of feels like bone). the suprascapular artery passes over the ligament and the suprascapular nerve passes under the ligament (army goes over the bridge, navy goes under the bridge)
2. suprascapular nerve innervates the infraspinatus and supraspinatus
3. suprascapular artery supplies the supraspinatus and infraspinatus as well as other structures along its course

Question 32

What are the borders of the triceps hiatus? What artery and nerve passes through this space?

Answer 32

superior border: teres major

medial border: long head of the triceps brachii

lateral border: humerus

the radial nerve and deep brachial artery pass through this space

Question 33

What are the borders of the triangular space? What artery passes through this space? What artery is it a branch of?

Answer 33

superior: teres minor
inferior: teres major
lateral: long head of the triceps brachii

circumflex scapular artery. it is a branch of the subscapular artery which leaves the axilla through the triangular space and wraps around the posterior aspect of the scapula to form anastomic connections with other arteries in the region