Muscles of the posterior shoulder week 2 Flashcards
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.
True.
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?
supraspinatus
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?
SItS
supraspinatus
infraspinatus
teres minor (reason for small t)
subscapularis
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
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
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.
True.
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.
trapezius
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?
- superior: teres minor
- medial: long head of triceps brachii
- inferior: teres major
- 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?
- 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)
- suprascapular nerve innervates the infraspinatus and supraspinatus
- 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
