The Shoulder joint, rotator cuff and shoulder musculature Flashcards
What is the shoulder joint?
Synovial ball and socket joint, where the ball is the head of the humerus and socket is the glenoid cavity.
The rim of cartilage surrounding the socket is the glenoid labrum.
What is the function of this cartilage?
Static stability to glenohumeral joint
What is the joint capsule of the glenohumeral joint thickened to form?
Definable ligaments, but true ligaments are also present between other bony elements.
Together these strengthen and ease movements at the joint.
What does the coracohumeral ligament do?
Strengthens superior aspect of the joint capsule.
The coraco-acromial arch is made up of what?
Acromion and coracoid process of scapula and coracromial ligament
It prevents superior displacement of the humeral head
Which part of the shoulder joint capsule is weakest, as it is not protected by muscles or ligaments?
Just anterior to the attachement of the long heads at the triceps at the infraglenoid tubercle
Why are bursae imporant?
They provide cushioning around joints via their synovial fluid filled interior – they essentially act as shock absorbers!
What are the 2 main bursa in thr shoulder?
Subacromial bursa
Subscapular bursa
Which bursa communicates with the joint cavity?
Subscapular
What is the role of subacromial bursa?
Gliding mechanism between the rotator cuff and coracoacromial arch
What common sporting injury damages the subacromial bursa?
Rotator cuff injury- subacromial bursitis
Which muscle is this?
Subscapularis
This is the subscapularis!
What is its proximal attachments?
Medial 2/3 of costal aspect of scapula
This is the subscapularis!
What is its distal attachments?
Lesser tuberosity, shoulder joint capsule and the front of the upper shaft of the humerus
What is the movement at the shoulder joint made by the subscapularis?
Adductor and medial rotator of the humerus
What muscle is this?
Supraspinatus
What are the proximal attachment of the supraspinatus?
Supraspinous fossa of the scapula and from fascia overlying the muscle
What are the distal attachment of the supraspinatus?
Greater tuberosity of humerus
What are the movements of the supraspinatus?
Initiates abduction
Hold humeral head in socket
What muscle is this?
Infraspinatus
What is the proximal attachment of the infraspinatus?
Infraspinous fossa of scapula
What are the distal attachement of the infraspinatus?
Medial facet of the greater tuberosity of the humerus
What are the movmenets of the shoulder joint by the infraspinatus muscle?
Lateral rotator of the humerus
Rotator cuff
What muscle is this?
Teres minor
What does the ters minor arise from?
Arises from upper 2/3 of lateral border of scapula
What is the distal attachment of the teres minor?
Lesser tuberosity of humerus
What is the movement at the shoulder joint by the teres minor?
Adductor and lateral rotator of the humerus
Rotator cuff
Although the rotator cuff muscles have a role in movement at the glenohumeral joint, what is their primary function?
Stabilise the rotator cuff
What are rotator cuff injuries caused by?
Repetitive overhead motions, e.g. serving in tennis; or throwing motions, e.g. pitching a baseball.
Over time the increased stress on the ligaments and muscles weakens them, making them more likely to tear.
Where does the deltoid muscle arise from?
Lateral spine of the scapula, passing across the acromion to the lateral third of the clavicle.
What is the distal attachment of the deltoid muscle?
Its distal attachment is to the deltoid tuberosity of the humerus
What are the actions of the deltoid muscle?
Anterior fibres of deltoid flexion and internal rotation at the shoulder joint
Middle fibres abducts the arm at the shoulder joint
Posterior fibres extension and external rotation at the shoulder joint
What is the nerve supply to the deltoid?
Axillary nerve (C5, C6)
In what common injury is this nerve often trapped and therefore damaged
Shoulder dislocation
As this is a mixed nerve, where would you test for loss of sensation to determine is a nerve injury had occurred?
Nerve conduction tests
What is the origin of pectoralis major muscle?
An extensive origin from the medial third of the clavicle, sternum and costal cartilage of the first 6 ribs and rectus sheath!
What is the distal attachment of the pectoralis major muscle?
The distal attachment of this muscle is to the greater lip of the bicipital groove of the humerus
What is the action of the pectoralis major muscle?
Its action on the shoulder joint is to adduct the shoulder and internally rotate the humerus at the glenohumeral joint.
Briefly describe the pectoralis muscle
Lies deep to pectoralis major
important anatomically as it splits the axillary artery into 3 parts
What does the pectoralis minor do?
Along with the serratus anterior it serves to stabilise the scapula during limb movements by keeping it pulled against the thoracic cage.
What does the serratus anterior from?
Interdigitations form the ribs and inserts into the scapula
What is the action of the serratus anterior?
It has an important role in protraction of the scapula.
What does the trapezius having a long origin mean?
Its fibres approach the spine of the scapulae from above, in-line and below it
What is the action of the trapezius?
Different movements upon contraction of different parts of the muscle.
What are the actions of the trapezius muscle?
Superior fibres of trapezius elevate the scapula
Middle fibres of trapezius adduct the scapula (move it back on the thorax)
Inferior fibres of trapezius depress the medial aspect of the scapula
Trapezius has an unusual innervation from a cranial nerve?
Accessory nere
Which foramen of the skull does the accessory nerve pass through?
Jugular foramen
What shoulder joint muscles cause flexion of shoulder?
Pectoralis major
Deltoid
Coracobrachialis
What shoulder joint muscles cause extension of shoulder?
Infraspinatus
Teres major
What shoulder joint muscles cause adduction of shoulder joint?
Pectoralis major
Latissimus dorsi
Teres major
Triceps
What shoulder joint muscles cause abduction of shoulder joint?
0-90 degrees
Supraspinatus
Middle fibres of the deltoid
90-180 degrees
Trapezius
Serratus anterior
What shoulder joint muscles cause medial or internal rotation?
Subscapularis
Lattisimus dorsi
Pectosalis major
Teres major
What shoulder joint muscles cause lateral or external rotation?
Infraspinatus
Teres minor
