Flashcards in MSK Session 3- Back And Shoulder Muscles, And The Shoulder Joint Deck (36)
What are intrinsic back muscles responsible for?
What are the three groups of extrinsic back muscles?
What are the two superficial back muscles?
What are the 2 deep back muscles?
What are the 2 scapulo-humeral muscles?
What is the action of each of the parts of the trapezius?
-descending/superior fibres- elevate and rotate the scapula
-middle fibres- retract the scapula
-ascending/inferior fibres- depress the scapula
-abduction past 90 degrees
What is the innervation of the trapezius muscle?
Spinal accessory nerve
What is the action of the latissimus dorsi?
Extension, adduction and medial rotation of the upper limb.
What is the innervation of the latissimus dorsi?
What is the action of the Levator scapulae muscle?
Elevates the scapula
What is the innervation to the Levator scapulae?
Dorsal scapula nerve
What is the action of the rhomboids?
Retraction and rotation of the scapula.
What is the innervation to the rhomboids?
Dorsal scapula nerve
Which rhomboid is most superior?
What is the action of the the three deltoid segments?
-anterior/clavicular fibres- flexion of the arm
-middle/acromial fibres - abduction of the arm between 15 and 90 degrees.
-posterior/spinal fibres - extension of the arm
What is the innervation to the deltoid muscle?
What is the action of teres major?
Adduction and medial rotation of the arm.
What is the innervation to teres major?
Lower subscapular nerve
What are the four rotator cuff muscles?
What is the general function of the rotator cuff muscles?
Support and stabilise the shoulder joint.
What is the action and innervation of supraspinatus?
Abduction up to 15 degrees
Innervation is the suprascapular nerve
What is the action and innervation of infraspinatus?
Lateral arm rotation.
Innervation- suprascapular nerve
What is the action and innervation of teres minor?
Action- lateral rotation and weak adduction
Innervation- axillary nerve
What is the action and innervation of subscapularis?
Action- medial rotation.
Innervation- upper and lower subscapular nerve
What is the articulation of the shoulder joint?
The head of the humerus sits in the glenoid cavity, which is deepened by the glenoid labrum.
What type of joint is the shoulder joint?
A ball and socket synovial joint
Why is the shoulder joint unstable and commonly dislocated? (4)
-the glenoid cavity is shallow
-the movements of the joint are multi planar
-the capsule is lax
-the articulating surfaces are disproportionate.
How is stability of the shoulder joint achieved? (4)
-rotator cuff muscles
Which way does the shoulder joint most commonly dislocate and why?
Inferiorly and anteriorly.
Because the inferior part of the capsule is the weakest as it is not reinforced by ligaments or the rotator cuff muscles.
What is the shoulder joint capsule?
A loose, fibrous layer.
Why is the capsule lax?
To allow full abduction of the arm
What are the five ligaments of the shoulder joint?
-glenohumeral- there are three of them (superior, middle and inferior) that move inferolaterally from the glenoid labrum-> humerus.
-coraco-acromial - between the acromion and coracoid process
-coraco-humeral - between the coracoid process and the greater tubercle
-transverse humeral - holds the long head of the biceps tendon in place during movement
-coraco-acromial arch - prevents upper displacement of the humeral head.
How is shoulder dislocation caused? (2)
-by excessive extension and lateral rotation
-trauma to a fully abducted arm
Which nerve can be injured during shoulder dislocation? What are the consequences?
The axillary nerve
Paralysis of the deltoid muscle and loss of sensation over the regimental patch area.
What is painful arc syndrome?
It is when the supraspinatous tendon rubs under to the coraco-acromial arch, causing irritation and inflammation of the tendon and subacromial bursa.