Muscles that Act on the shoulder Flashcards
What three bones is the pectoral girdle made of?
Clavicle, scapula, humerus
What is the role of the pectoral girdle?
Connects axial to appendicular skeleton, full range of motion in upper limb.
What are the joints and articulations of the pectoral girdle?
Sternocostal, sternoclavicular, acromioclavicular, glenohumeral, costovertebral, scapulothoracic, interclavicular
How does the glenohumeral joint stay in place?
Muscles, joint capsule, ligaments
What is the glenoid labrum?
Fibrocartilage, deepends glenoid fossa by 5-9 mm, creates a wall that creates for articular space for humeral head.
What are the ranges of motion for the glenohumeral joint?
Flexion/extension, adduction and abduction, internal and external rotation, circumduction
Coracohumeral ligament
Resists inferior and posterior translation, connects at coracoid process and greater tubercle of humerus
Glenohumeral ligament
Resists anterior displacement of the humeral head. Connects anatomical neck of humerus and scapula. Tightens with external rotation
What muscles flex the shoulder?
Deltoid, pectoralis major, biceps brachii, coracobrachialis
What muscles extend the shoulder?
Deltoid, latissimus dorsi, teres major, pec major, triceps brachii
Deltoid muscle:
Origin: Anterior border and upper surface of the lateral 1/3 of the clavicle, acromion and the spine of the scapula.
Insertion: Deltoid tuberosity of the humerus
Action: Abduction, flexion, extension of the shoulder
Innervation: Axillary nerve
Pectoralis Major
Origin: Sternocostal head: superior costal 6 cartilages, ant surface sternum
Clavicular head: ant surface medial half clavicle
Insertion: lateral lip of the bicipital groove of humerus
Action: adducts, medially rotates humerus, flexion
Innervation: Lateral and medical pectoral nerves
Coracobrachialis
Origin: Coracoid process of scapula
Insertion: middle 1/3 medial surface of humerus
Action: flexion and adduction of shoulder
Innervation: musculocutaneous nerve
Latissimus Dorsi
Origin: spinous processes of 6 thoracic vertebrae, iliac crest, thoracolumbar fascia, inferior ribs 3-5
Insertion: Floor of the intertubercular groove
Action: extends, adducts, and medially rotates the humerus. Tilts pelvis anteriorly and laterally, bilaterally acts in hyperextending the spine depending on the orientation of the pelvis
Innervation: Thoracodorsal nerve
Teres major
Origin: Posterior aspect of the inferior angle of the scapula
Insertion: medial lip of the bicipital groove of the humerus
Action: adduction, medial rotation, extension
Innervation: Lower subscapular
What muscles ABduct the shoulder?
Deltoid, supraspinatus
What muscles ADDuct the shoulder?
Coracobrachialis, pec major, latissimus dorsi, teres major
What muscles medial rotate the shoulder?
Pec major, latissiumus dorsi, teres major, subscapularis
What muscles laterally rotate the shoulder?
Infraspinatus, teres minor
Infraspinatus
Origin: infraspinous fossa of the scapula
Insertion: middle facet of greater tubercle
Action: laterally rotates
Innervation: Subscapular nerve
Teres minor
Origin: Middle part of the lateral border of the scapula
Insertion: Inferior facet of greater tubercle
Action: laterally rotates
Innervation: Axillary nerve
Subscapularis
Origin: Subscapular fossa of the scapula
Insertion: Lesser tubercle of the humerus
Action: Medially rotates
Supraspinatus
Origin: Supraspinous fossa of the scapula
Insertion: Superior facet of the greater tubercle of the humerus
Action: Abduction
Where is the medial wall of the Axilla?
Serratus anterior/thoracic wall
