Shoulder Girdle-origin/insertion/action Flashcards
What is the shoulder/pectoral girdle?
The attachment point of the upper-limb to the axial skeleton
What is the relationship between stability and mobility?
If something has high mobility then its stability is poor and vice versa
Does the shoulder girdle have high mobility or stability?
High mobility due to ball and socket, therfore prone to injury.
What are the 7 joints/articulations of the pectoral girdle?
sternocostal, sternoclavicular, acromioclavicular, glenohumeral, costovertebral, scapulothoracic, interclavicular
What is the range of motion and joint type for the Sternoclavicular joint?
Saddle joint. Movements include full elevation to 60 degrees between the clavicle and midline. Anterior and posterior movement. 25-30 degree protraction and retraction
What are the ligaments of the sternoclavicular joint?
Interclavicular, costoclavicular, sternoclavicular
Interclavicular Ligament
Limits superior and lateral displacement of the clavicle
Costoclavicular Ligament
Main support, limits all ranges of motion except depression
Sternoclavicular ligament
Limits anterior and posterior glide of clavicle
What is the acromioclavicular joint type?
Plane joint
What does the acromioclavicular do?
Serves as a restriction to over-head arm movements
What are the ligaments of the acromioclavicular joint?
Coracoclavicular, acromioclavicular, coracoacromioal
Coracoclavicular ligament
Conoid and trapezoid, primary restraint to vertical displacement
Acromioclavicular ligament
Prevents separation of clavicle and scapula. Prevents posterior and anterior displacement
Coracoacromial ligament
Forms roof over the glenohumeral joint. Protection for bursa and supraspinatus tendon. Provides limit to superior humeral head movement
Scapulothoracic joint.
Physiologic articulation between rib cage and scapula.
What are the movements of the scapulothoracic joint?
Elevation, depression, adduction, abduction, upward rotation, downward rotation
What is the function of the scapulothoracic joint?
Allows the arm to abduct beyonf 120 degrees. Allowed by the glenohumeral joint, 1 degree of scapular rotation for every 2 degrees of humeral abduction.
What three directions does the scapulothoracic joint move in?
Protraction and retraction (30-60), superior and inferior rotation (60), elevation and depression (30)
What are the muscles that protract the scapula?
Serratus anterior, pectoralis major, and pectoralis minor
What muscles retract the scapula?
Trapezius (middle part) and the rhomboids
Serratus Anterior:
Origin: External layer of the lateral parts of rubs 1-8
Insertion: Anterior surface of the medial border of the scapula
Action: Protracts the scapula and holds it against the thoracic wall; rotates the scapula in an upward direction
Innervation: Long thoracic nerve
What does a blow to the serratus anterior induce
Winging
Pectoralis Major
Origin: 2 heads, clavicular head (anterior surface of the medial half of the clavicle) and sternocostal head (anterior surface of the sternum, superior six costal cartilages, aponeurosis of external oblique muscle)
Insertion: Lateral lip of the intertubercular groove of the humerus
Actions: Adducts and medially rotates the humerus. Draws the scapula anteriorly and inferiorly. Acting alone the clavicular head flexes the humerus, and the sternocostal head will extend the humerus from a flexed position.
Innervation: Lateral and medical pectoral nerves. Clavicular head, sternocostal head.
Pectoralis Minor
Origin: Ant. surface of ribs 3,4,5
Insertion: Coracoid process of the scapula
Action; anchors, depresses, protracts the scapula
Innervation: medical pectoral
Trapezius (Middle fibers)
Origin: Spinous processes of the first-fifth thoracic vertebrae
Insertion: Medial margin of the acromion and superior lip of the spine of scapula
Action: retracts scapula
Innervation: Spinal accessory nerve
Rhomboids
Origin: Spinous processes of the thoracic vertebrae 2-5 (major). Ligamenteum Nuchae, spinous process of 7th cervical and 1st thoracic vertebrae (minor)
Insertion; Fibrous attachment to the medial border of the scapula between the spine and inferior angle (major). Medial border of the scapula, at the root of the spine of the scapula (minor).
Action: Adducts and elevates the scapula, downwardly rotates the scapula
Innervation: Dorsal scapular nerve
Which muscles elevate the scapula
Levator scapulae, trapezius, rhomboids
Trapezius (upper fibres)
Origin: External occipital protuberance, ligamentum nuchae and spinous process of the 7th cervical vertebrae
Insertion: Lateral 1/3 of the clavicle and acromion process of scapula
Action: Elevates scapula
Innervation: Spinal Accessory nerve
Levator Scapulae
Origin: Transverse processes of the first 4 cervical vertebrae
Insertion: Medial border of the scapula, between the superior angle and the root of the spine
Action: Elevates scapula and assists with downward rotation of the scapula. Can also assist with lateral flextion of c-spine or extension of the c-spine if the scapula is stabilized by other muscles
Innervation: Cervical 3+4 and dorsal scapular nerve
What muscles cause depression of the scapula?
Trapezius (lower part) , subclavius, pectoralis minor, gravity
Trapezius (lower fibres)
Origin: Spinous processes of the 6th-12th thoracic vertebrae
Insertion; Tubercle at the apex of the spine of the scapula
Action: Depresses the scapula
Innervation: Spinal accessory nerve
Which muscles rotate the scapula upward?
Trapezius (upper/lower fibres), serratus anterior
Which muscles downwardly rotate the scapula?
Levator scapulae, rhomboids, pectoralis minor, gravity
