Shoulder muscles (wk7) Flashcards
Describe the function, origin and insertion of the muscles that create movement at the scapula
-Trapezius (upper, middle, lower), Levator scapulae and the rhomboids (major)
- Trapezius (upper, middle, lower) -> O: External occipital protuberance and superior nuchal line of occipital bone, spinal process of C7 to T12, I: Posterior aspect of lateral clavicle, acromion and spine of scapula, F: Elevates, depresses, retracts and upwardly rotates the pectoral girdle
- Levator scapulae -> O: Transverse process of C1-C2 vertebrae and posterior of C3-C4 vertebrae, I: Superior angle of scapula, F: Elevates and downwardly rotates shoulder girdle at acromioclavicular and sternoclavicular joints
- The Rhomboids (major) -> O: Spinous processes of T2-T5 vertebrae, I: Medial border of scapula inferior to spine of scapula, F: Retracts and downwardly rotates shoulder girdle at acromioclavicular and sternoclavicular joints
Describe the function, origin and insertion of the muscles that create movement at the scapula
-Latissimus dorsi, Subclavius, Pectoralis minor
- Latissimus dorsi -> O: Spinous processes of T7-T12 vertebrae and spinous processes of L1-L5 vertebrae, I: Floor of intertubercular of humerus, F: Adducts, medially rotates and extends arm at glenohumeral joint
- Subclavius -> F: Superior surface of costal end of first rib, I: Inferior surface of the middle of the clavicle, F: Stabilizes clavicle
- Pectoralis minor -> O: Anterior ends of 3rd to 5th ribs, I: Coracoid process of scapula, F: Protracts and downwardly rotates pectoral girdle at acromioclavicular and sternoclavicular joints
Describe the function, origin and insertion of the muscles that create movement at the scapula
-Serratus anterior, pectoralis minor
- Serratus anterior -> O: External surface of 5th to 9th ribs, I: Medial border of scapula, F: Protracts and upwardly rotates shoulder girdle at acromioclavicular and sternoclavicular joints
- Pectoralis major -> O: Clavicular head, sternocostal head and abdominal part, I: Crest of greater tubercule of humerus, F: Adducts, medially rotates and transversely adducts arm at glenohumeral joint, depresses pectoral girdle at acromioclavicular and sternoclavicular joints
Explain how the muscles work together
-Scapular elevation, depression and retraction
- Scapular elevation -> Trapezius and elevator of scapula
- Depression -> When the pectoralis major muscle contracts, it can generate the movement of depression. Lower part of the trapezius, pectoralis minor and latissimus dorsi – they are inserted into the humerus but the combined action can create depression.
- Retraction -> Several muscles, including: trapezius, latissimus dorsi, rhomboid major and minor.
Explain how these muscles work together
-Protraction, lateral rotation and upward rotation of the scapula
- Protraction -> Pectoralis minor and serratus anterior are the main muscles used. When both contract, the scapula glides and moves the medial border of the scapula from the spinal processes.
- Lateral rotation -> Upper fibres of trapezius, serratus anterior – which pull the inferior angles of the scapula upwards and some fibres of the lower part of the trapezius pull the scapula down.
- Upward rotation of scapula -> Muscles includes: descending fibres of trapezius, serratus pulling the inferior angle of the scapula upwards and the upper fibres of the trapezius.
-The rotation is executed by a combination of factors, such as the elevation of the levator scapulae, rhomboids and the pectoralis minor pulling the coracoid process to perform this movement.
Describe the bony landmarks of the humerus
-Infra glenoid and supraglenoid tubercule
- Infraglenoid tubercule -> Part of the scapula from which the long head of the triceps brachii originates. It is located on the lateral part of the scapula, inferior to the glenoid cavity.
- Supraglenoid tubercule -> Region of the scapula which the long head of the biceps brachii muscle originates. It’s a small, rough projection superior to the glenoid cavity near the base of the coracoid process.
Describe the bony landmarks of the humerus
-Greater tuberosity, lesser tuberosity and capitulum
-Greater tuberosity -> Large, posteriorly placed projection that is located laterally to the head of the humerus. It is the attachment point for three rotator cuff muscles: supraspinatus, infraspinatus and teres minor.
-Lesser tuberosity -> Although smaller, is more prominent than the greater tubercule. It’s located at the front and is directed medially and anteriorly.
-Capitulum -> Smooth, rounded eminence on the lateral portion of the distal articular surface of the humerus
Describe the bony landmarks of the humerus
-Medial epicondyle, trochlea and lateral epicondyle
-Medial epicondyle -> Larger and more prominent than the lateral epicondyle and is directed slightly more posteriorly in the anatomical position.
-Trochlea -> The humeral trochlea is the medial portion of the articular surface of the elbow joint which articulates with the trochlear notch on the ulna in the forearm
-Lateral epicondyle -> A bony prominence on the outer side of the elbow joint. It gives attachment to the radial collateral ligament of the elbow joint and to several extensor muscles of the forearm.
Describe the bony landmarks found on the humerus
-Radial fossa and deltoid tuberosity
-Radial fossa -> A slight depression found on the humerus above the front part of the capitulum. It receives the anterior border of the head of the radius when the forearm is flexed.
-Deltoid tuberosity -> A rough, triangular area on the middle of the lateral side of the humerus. It is a site of attachment for the deltoid muscles which is a large muscle that covers the shoulder joint.
Describe the function, origin and insertion of the muscles that create abduction at GHJ
-Middle deltoid and supraspinatus
- Middle deltoid -> O: Acromion of the scapula, lateral part of clavicle and spine, I: Deltoid tuberosity of humerus, F: Shoulder abduction, stabilize glenohumeral joint and the swinging of arms when walking.
- Supraspinatus -> O: Supraspinous fossa of the scapula, I: Greater tubercule of the humerus, F: Helps to resist the gravitational forces which ats on the shoulder joint to pull from the weight of the upper limb downward
Describe the function, origin and insertion of the muscles that create adduction at the GHJ
-Latissimus dorsi and teres major
- Latissimus dorsi -> O: Spinous processes of thoracic T7-T12, thoracolumbar fascia, iliac crest and inferior 3 or 4 ribs, inferior angle of scapular, I: Floor of intertubercular grove of the humerus, F: Pull the inferior angle of the scapula in various directions, producing movements on the shoulder arm (internal rotation, adduction and extension of the arm)
- Teres major -> O: Dorsal surface of the inferior angle and the lower part of lateral border of the scapula, I: Medial lip of the intertubercular groove of the humerus, F: Extend, adduct, and internally rotate the humerus
Describe the function, origin and insertion of the muscles that create adduction at the GHJ
-Coracobrachialis and pectoralis minor
- Coracobrachialis -> O: Coracoid process of the scapula, I: The shaft of the humerus, F: Flexion and adduction of the shoulder joint
- Pectoralis major -> O: Greater tubercule of the humerus, I: Lateral lip of the intertubercular sulcus of the humerus, F: Strong adductor and internal rotator of the humerus at the shoulder joint
Describe the function, origin and insertion of the muscles that create flexion at the GHJ:
-Anterior deltoid and pectoralis minor
- Anterior deltoid -> O: Lateral third of the clavicle, I: Deltoid tuberosity of the humerus, F: Stabilisation of the shoulder joint, preventing subluxation or dislocation of the head of the humerus, when carrying a load
- Pectoralis major -> 3rd-5th ribs, I: Coracoid process of the scapula, F: Stabilise the scapula by holding it fast in position against the chest wall
Describe the function, origin and insertion of the muscles that create flexion at the GHJ:
-Biceps brachii and Coracobrachialis
- Biceps brachii -> O: (long head) Supraglenoid tubercule of the scapula , (short head) coracoid process of the scapula, I: (both heads) inset distally into the radial tuberosity and the fascia of the forearm via the bicipital aponeurosis, F: flexion and supination/ outward rotation of the forearm
- Coracobrachialis -> O: Coracoid process of the scapula, I: The shaft of the humerus, F: Flexion and adduction of the shoulder joint
Describe the function, origin and insertion of the muscles that create extension at the GHJ:
-Posterior deltoid, latissimus dorsi and long head of triceps brachii
- Posterior deltoid -> O: Spine of the scapula, I: Deltoid tuberosity of the humerus, F: Extension, external rotation and horizontal abduction
- Latissimus dorsi -> O: Spinous processes of thoracic T7-T12, thoracolumbar fascia, iliac crest and inferior 3 or 4 ribs, inferior angle of scapular, I: Floor of intertubercular grove of the humerus, F: Pull the inferior angle of the scapula in various directions, producing movements on the shoulder arm (internal rotation, adduction and extension of the arm)
- Long head of triceps brachii -> O: Infraglenoid tubercule of the scapula, I: Both the lateral and medial head insert onto the olecranon of the ulna, F: Acts to hold the head of the humerus in the glenoid cavity, which prevents any displacement of the humerus. It assists with the extension and adduction of the arm at the shoulder joint.
