shoulder anatomy Flashcards
What are the bones of the shoulder girdle?
Scapula, Humerus, Clavicle
What joints are part of the shoulder girdle?
Glenohumeral joint, Acromioclavicular joint, Sternoclavicular joint, Scapulothoracic joint
What type of joint is the Glenohumeral joint?
Multiaxial synovial ball-and-socket joint
What are the articulating surfaces of the Glenohumeral joint?
Humeral head and glenoid fossa of the scapula
What structure deepens the glenoid cavity?
Glenoid labrum
What is the function of the glenoid labrum?
Deepens the cavity and increases surface area
What ligaments are found in the Glenohumeral joint?
- Superior Glenohumeral ligament * Middle Glenohumeral ligament * Inferior Glenohumeral ligament * Coracohumeral ligament * Transverse Humeral ligament
What is the role of the coraco-acromial arch?
Prevents superior displacement of the humeral head from the glenoid cavity
What is the function of the bursae in the Glenohumeral joint?
Reduce friction between tendons and bones
What type of joint is the Acromioclavicular joint?
Plane synovial joint
What ligaments stabilize the Acromioclavicular joint?
- Acromioclavicular ligament * Coracoclavicular ligaments (trapezoid and conoid)
What is the significance of the Sternoclavicular joint?
Only articulation between the upper limb and the axial skeleton
What type of joint is the Sternoclavicular joint?
Synovial, saddle-type joint
What are the movements allowed by the Sternoclavicular joint?
- Elevation * Depression * Protraction * Retraction * Rotation
What is the scapulothoracic joint?
Not a true anatomical joint formed by the thoracic cage and scapula
What are the movements at the shoulder joints?
- Abduction - 180 degrees * Adduction - 45 degrees * Flexion - 180 degrees * Extension - 60 degrees * Lateral Rotation - 90 degrees * Medial Rotation - 70-90 degrees
What is the scapulohumeral rhythm?
Ratio of GHJ movement to STJ movement during arm elevation
What is the widely accepted ratio of GH elevation to ST upward rotation?
2:1 ratio
What muscles are considered primary dynamic stabilizers of the Glenohumeral joint?
Rotator cuff muscles: Supraspinatus, Infraspinatus, Teres Minor
What is the primary function of the trapezius muscle?
- Elevates scapula * Depresses scapula * Retracts scapula * Rotates scapula superiorly
Fill in the blank: The ________ ligament limits elevation of the pectoral girdle.
Costoclavicular ligament
True or False: The scapulothoracic joint allows for a stable base for the Glenohumeral joint.
True
What is the significance of the scapula’s position during arm movements?
Orientates the glenoid into an optimal position for GHJ function
What is the role of the subscapularis muscle?
Internal rotation of the humerus
What is the function of the long head of the biceps brachii?
Flexes elbow and supinates forearm
What movements occur at the Scapulothoracic joint?
- Elevation * Depression * Protraction * Retraction * Upward rotation * Downward rotation
What stabilizes the Glenohumeral joint?
- Surrounding muscles and tendons * Coraco-acromial arch * Glenoid labrum
What is the importance of the fibrocartilage articular disc in the Sternoclavicular joint?
Acts as a shock absorber
What is the function of passive stabilisers in the shoulder joint?
Provide some stability
Passive stabilisers include structures like the glenoid labrum and ligaments that help stabilize the joint without active muscle contraction.
What role does the glenoid labrum play in the shoulder joint?
Deepens socket depth and creates a cavity-compression ‘suction’ effect
The glenoid labrum is a fibrocartilaginous structure that enhances the stability of the shoulder joint.
What is the significance of negative intra-articular pressure in the shoulder joint?
Helps in centring the humeral head
Negative pressure within the joint contributes to joint stability by keeping the humeral head properly aligned.
What are the primary dynamic stabilisers of the glenohumeral joint?
Rotator cuff muscles and long head of biceps
The rotator cuff includes the supraspinatus, infraspinatus, teres minor, and subscapularis.
Which muscle limits excessive superior translation of the humeral head?
Supraspinatus
The supraspinatus is positioned superiorly and plays a critical role in stabilizing the shoulder.
What muscles are involved in the upward rotation of the scapula?
Upper traps, lower traps, serratus anterior
These muscles work together to facilitate the upward movement of the scapula during arm elevation.
Fill in the blank: The _______ lies posterior and limits excessive superior and posterior translation of the humeral head.
Infraspinatus and Teres minor
True or False: The deltoid muscle prevents subluxation or dislocation of the humeral head when carrying load.
True
The deltoid provides dynamic stabilization, especially during weight-bearing activities.
What are the muscles responsible for shoulder flexion?
Pectoralis Major, deltoid (anterior), long and short head of biceps, coracobrachialis
These muscles contract to lift the arm forward.
What is the role of axio-appendicular muscles in shoulder stability?
Important for optimal scapula positioning during static postures and with movement
These muscles connect the axial skeleton to the appendicular skeleton and play a key role in shoulder mechanics.
Which muscles are involved in shoulder adduction?
Latissimus Dorsi, Teres Major
These muscles pull the arm towards the body, facilitating adduction.
List the muscles involved in shoulder extension.
- Latissimus dorsi
- Triceps
- Teres major
These muscles are responsible for moving the arm backward.
Fill in the blank: The _______ is a weakened region of the rotator cuff reinforced by the long head of biceps and coracohumeral ligament.
Rotator cuff interval
What limits excessive anterior and superior translation of the humeral head?
Subscapularis
The subscapularis muscle is located anteriorly and provides stability against forward dislocation.
What is the main function of the rotator cuff?
Protects and actively stabilises the GHJ during static and dynamic activities
The rotator cuff keeps the humeral head centred in the glenoid fossa.
Which muscles are responsible for lateral rotation of the shoulder?
Teres minor, Infraspinatus, Deltoid (posterior)
These muscles allow the arm to rotate away from the body.
What are the movements associated with the scapulothoracic joint?
- Protraction
- Retraction
- Depression
- Elevation
- Downward Rotation
- Upward Rotation
These movements are essential for shoulder function and range of motion.
