Dissection 10- Posterior Shoulder and Rotator Cuff Muscles Flashcards
What is the pectoral girdle and what is it composed of?
A bony ring, incomplete posteriorly, formed by the scapulae and the clavicles and completed anteriorly by the manubrium of the sternum
What does the sternal end of the clavicle articulate with? What is this joint called?
Articulates with the manubrium of the sternum, forming the sterno-clavicular joint
What does the acromial end of the clavicle articulate with? What is this joint called?
Acromion of the scapula at the acromioclavicular joint
What is the function of the pectoral girdle?
Permits articulation of the upper limb with the appendicular skeleton to offer an increased range of movement for hand function
What 3 joints make up the pectoral girdle?
Sternoclavicular, acromioclavicular and gleno-humeral
The pectoral girdle has a role in maintaining what position of the upper limb?
The relatively lateral position of the upper limb
How is the pectoral girdle stabilised?
By providing attachment points for ligaments and muscles
What are the 3 groups of posterior shoulder muscles?
Superficial posterior axio-appendicular
Deep posterior axio-appendicular
Scapulohumeral
What muscles are in the superficial posterior axio-appendicular group?
Trapezius and latissimus dorsi
What muscles are in the deep posterior axio-appendicular group?
Rhomboids and levator scapulae
What muscles are in the scapulohumeral group?
Deltoid, teres major, 4 rotator cuff muscles
Which of the posterior shoulder muscle groups are extrinsic shoulder muscles?
Superficial posterior axio-appendicular
Deep posterior axio-appendicular
Which of the posterior shoulder muscle groups are intrinsic shoulder muscles?
Scapulohumeral
Describe the trapezius muscle and where it is found?
A large, triangular muscle covering the posterior aspect of the neck, and the superior half of the trunk
How many parts is the trapezius muscle divided into?
These parts all have different actions where?
3 parts
Different actions at the joint between the scapula and thoracic wall
What are the 3 parts of the trapezius known as?
Ascending, middle and descending
What is the action of the descending part of the trapezius?
Elevates the scapula
What is the action of the middle part of the trapezius?
Retracts scapula (pulls posteriorly)
What is the action of the ascending part of the trapezius?
Depresses scapula/lowers shoulder
The ascending and descending parts of the trapezius work together to allow what movement?
Superior rotation of the glenoid fossa (rotation of the scapula)
Weakness of the trapezius causes what?
Drooping of the shoulders
What innervates the trapezius?
Spinal accessory nerve (CNXI) for motor
C3/4 spinal nerves for pain and proprioception
Describe the latissimus dorsi and where it passes?
A large fan shaped muscle which covers a wide area of the back, passing from trunk to humerus
The latissimus dorsi can ‘raise trunk to arm’, along with what other muscle?
Pectoralis major
As well as the climbing action, what are some other actions of the latissimus dorsi?
Extends, adducts and medially rotates the shoulder
What is the nerve supply to the latissimus dorsi?
Thoracodorsal nerve
Where do the superior and inferior thirds of the levator scapulae muscle lie?
Superior- deep to SCM
Inferior- deep to trapezius
The levator scapulae acts with what other muscle to produce what action?
Elevates the scapula with the descending part of the trapezius
The levator scapulae can rotate the scapula (inferior rotation of the glenoid fossa) with which other two muscles?
Rhomboids and pectoralis minor
Where are the rhomboids found?
They lie deep to the trapezius, and form two parallel bands which pass inferolaterally from the vertebrae to the medial border of the scapula
What are the actions of the rhomboids?
Retract the scapula
Rotate the scapula (inferior rotation of the glenoid fossa)
What are both the deep posterior axio-appendicular muscles (levator scapulae and rhomboids) supplied by?
Dorsal scapular nerve
Describe the scapulohumeral muscles and where they supply?
Relatively short muscles which pass from the scapula to the humerus and act on the glenohumeral joint
What is a thick, powerful muscle which forms the rounded contour of the shoulder?
Deltoid
What are the 3 parts of the deltoid?
- Clavicular (anterior)
- Acromial (middle)
- Spinal (posterior)
What happens when all three of the deltoid muscles are contracted at once?
The shoulder joint is abducted
Does the deltoid muscle initiate abduction?
No
The deltoid can act as a shunt muscle to try and prevent what injury?
Inferior displacement of the head of the humerus
What is the action of the spinal part of the deltoid?
Extension of the arm at the shoulder joint
What is the action of the acromial part of the deltoid?
Abduction of shoulder (beyond 15 degrees)
What is the action of the clavicular part of the deltoid?
Flexion of the arm at the shoulder joint
What are the proximal attachments of the deltoid?
Lateral 1/3rd of clavicle and the acromion/spine of scapula
What is the distal attachment of the deltoid?
Deltoid tuberosity of humerus
What innervates the deltoid?
Axillary nerve
What must happen in order for full adduction/abduction of the shoulder to occur?
The scapula must rotate so that the glenoid fossa faces more inferiorly/superiorly respectively
What is required to prevent the greater tubercle of the humerus from impugning on the acromion of scapula?
Superior rotation of the glenoid
What is a thick, rounded muscle which lies on the inferolateral 1/3rd of of the scapula?
Teres major
What are the actions of the teres major?
- Adducts arm
- Medially rotates arm
- Stabiliser of the humeral head in the glenoid fossa
What innervates the teres major?
Lower sub scapular nerve
What muscles make up the rotator cuff?
Supraspinatus, infraspinatus, teres minor, subscapularis
Which of the rotator cuff muscles is not a rotator of the humerus?
Supraspinatus
What is the function of supraspinatus?
First 15 degrees of abduction of shoulder
What are the functions of infraspinatus?
Stabilises head of humerus in glenoid
Lateral rotation of shoulder
What are the functions of teres minor?
Stabilises head of humerus in glenoid
Lateral rotation of shoulder
What are the functions of subscapularis?
Stabilises head of humerus in glenoid
Medial rotation of shoulder
Where do the distal tendons of the rotator cuff muscles go?
They blend with and reinforce the fibrous joint capsule of the shoulder
Where do the rotator cuff muscles insert?
Scapula
Where do the supraspinatus, infraspinatus and teres minor muscles attach?
Greater tubercle of humerus
Where does the subscapularis muscles attach?
Lesser tubercle of humerus
What is the nerve supply to supraspinatus?
Suprascapular nerve
What is the nerve supply to infraspinatus?
Suprascapular nerve
What is the nerve supply to teres minor?
Axillary nerve
What is the nerve supply to subscapularis?
Upper and lower subscapular nerves
The nerves supplying the rotator cuff muscles are all branches of what?
The brachial plexus
What causes painful arc syndrome?
Impingement of the supraspinatus tendon between the humerus and acromion process
When will patients will painful arc syndrome have pain?
50-130 degrees of abduction
What patients will throw their upper limb to the side to initiate abduction?
Those with supraspinatus paralysis/tear
What are 2 common fractures of the pectoral girdle?
Middle third of the clavicle
Surgical/mid-shaft of the humerus
What joint of the pectoral girdle is commonly subluxated/dislocated?
Acromioclavicular joint
What is the most common rotator cuff injury?
Partial tear/complete rupture of the supraspinatus tendon