Muscles of the posterior shoulder week 2 Flashcards Preview

MSK M1 > Muscles of the posterior shoulder week 2 > Flashcards

Flashcards in Muscles of the posterior shoulder week 2 Deck (34):

How are origins and insertions defined?

origins: proximal attachment sites

insertions: distal attachment sites


concentric contraction

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


eccentric contraction

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)


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.

concentric and eccentric


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



What are reasons for rotator cuff injuries?

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. 


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



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

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


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

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


Identify the bony landmarks of the posterior scapula.


Identify the bony landmarks of the anterior scapula.


Identify the bony landmarks of the humerus.


Identify the ligaments of the shoulder complex. 


What muscles are part of the rotator cuff?




teres minor (reason for small t)



Identify these muscles. What do these muscles comprise?

rotator cuff


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

deltoid and teres major


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

origin: lateral 1/3 of the clavicle, spine of the scapula, acromion process of the scapula

insertion: deltoid tuberosity of humerus


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


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

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


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

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


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

origin: infraspinous fossa of scapula

insertion: greater tubercle of humerus

function: laterally rotates arm at the glenohumeral joint

innervation: suprascapular nerve


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

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


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

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


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

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


Identify the muscles in this picture. 


What is the name of this muscle?


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?

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


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. 



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

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.


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. 



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?

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


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

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


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

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



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

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