Pectoral girdle and shoulder joint Flashcards
Extrinsic muscles of the shoulder
Origionate from the torso, and attach to the bones of the shoulder (clavicle, scapula or humerus)
Intrinsic muscles of the shoulder
Origionate from the scapula and/or clavicle, and attach to the humerus
What are the intrinsic muscles of the shoulder (scapulohumeral group)?
- deltoid
- teres major
- rotator cuff muscles
- supraspinatus
- infraspinatus
- subscapularis
- teres minor
Deltoid attachments
Origionate from the lateral third of the clavicle, the acromion and the spine of the scapula. It attaches to the deltoid tubercle on the lateral aspect of the humerus.
Deltoid innervation
Axillary nerve
Deltoid actions
- Anterior fibres - flexion and medial rotation
- Middle fibres - the major abductor of the arm (takes over from the supraspinatus which abducts the first 15 degrees)
- Posterior fibres - extension and lateral rotation
Teres major attachments
Origionates from the posterior surface of the inferior angle of the scapula. It attaches to the medial lip of the intertubercular groove of the humerus.
Teres major innervation
Lower subscapular nerve
Teres major actions
Adducts at the shoulder and medially rotates the arm
Rotator cuff muscles collective function
Gives the glenohumeral joint additional stability
Supraspinatus attachments
Origionates from the supraspinous fossa of the scapula, attaches to the greater tubercle of the humerus.
Supraspinatus innervation
Suprascapular nerve
Supraspinatus action
Abducts the arm 0-15 degrees, assists deltoid for 15-90 degrees.
Infraspinatus attachments
Origionates from the infraspinatus fossa of the scapula, attaches to the greater tubercle of the humerus.
Infraspinatus innervation
Suprascapular nerve
Infraspinatus actions
Laterally rotates the arm
Subscapularis attachments
Origionates from the subscapular fossa, on the costal surface of the scapula. It attaches to the lesser tubercle of the humerus.
Subscapularis innervation
Upper and lower subscapular nerves
Subscapularis actions
Medially rotates the arm
Teres minor attachements
Origionates from the posterior surface of the scapula, adjacent to its lateral border. It attaches to the greater tubercle of the humerus.
Teres minor innervation
Axillary nerve
Teres minor actions
Laterally rotates arm
What are the extrinsic muscles of the shoulder?
- Superficial
- trapezius
- latissumus dorsi
- Deep
- levator scapulae
- rhomboids
Trapezius attachments
Origionates from the skull, nuchal ligaments and spinous processes of C7-T12. The fibres attach to the clavicle, acromion and the scapula spine.
Trapezius innervation
Motor innervation is from the accessory nerve. It also recieves proprioceptor fibres from C3 and C4 spinal nerves.
Trapezius actions
- Upper fibres - elevates scapula and rotates it during abduction of the arm
- Middle fibres - retract the scapula
- Lower fibres - pull the scapula inferiorly
Latissimus dorsi attachments
Has a broad origin - arising from the spinous processes of T7-T12, iliac crest, thoracolumber fascia, and the inferior three ribs. The fibres converge into a tendon that attaches to the intertubercular sulcus of the humerus.
Latissimus dorsi innervation
Thoracodorsal nerve
Latissimus dorsi actions
Extents, adducts and medially rotates the upper limb
Levator scapulae attachments
Origionates from the transverse processes of the C1-C4 vertebrae and attaches to the medial border of the scapula.
Levator scapulae innervation
Dorsal scapular nerve
Levator scapulae actions
Elevates the scapula
Rhomboid major attachments
Origionates from the spinous processes of T2-T5 vertebrae. Attaches to the medial border of the scapula between the scapula spine and inferioir angle.
Rhomboid major innervation
Dorsal scapular nerve
Rhomboid major actions
Retracts and rotates the scapula
Rhomboid minor attachments
Origionates from the spinous processes of C7-T1 vertebrae. Attaches to the medial border of the scapula, at the level of the spine of scapula.
Rhomboid minor innervation
Dorsal scapular nerve
Rhomboid minor actions
Retracts and rotates the scapula
What are the muscles of the pectoral region?
Pectoralis major, pectoralis minor, serratus anterior and subclavius
Pectoralis major attachments
- The distal attachment of both heads is into the intertubercular sulcus of the humerus.
- Clavicular head origionates from the anterior surface of the medial clavicle.
- Sternocosal head origionates from the anterior surface of the sternum, the superior six costal cartilages and the aponeurosis of the external oblique muscle.
Pectoralis major function
Adducts and medially rotates the upper limb, and draws the scapula anterioinferiorly. The clavicular head also acts individually to flex the upper limb.
Pectoralis major innervation
Lateral and medial petoral nerves
Pectoralis minor attachment
Origionates from the 3rd to 5th ribs, and inserts into the coracoid process of the scapula.
Pectoralis minor function
Stabilises the scapula by drawing it anterioinferiorly against the thoracic wall
Pectoralis minor innervation
Medial pectoral nerve
Serratus anterior attachments
The muscle consists of several strips, which origionate from the lateral aspects of ribs 1-8. They attach to the costal surfaces of the medial border of the scapula.
Serratus anterior function
Rotates the scapula, allowing the arm to be raised over 90 degrees. It also holds the scapula against the rib cage.
Serratus anterior innervation
Long thoracic nerve
Subclavius attachments
Originates from the junction of the 1st rib and its costal cartilage, inserting into the inferior surface of the middle third of the clavicle.
Subclavius function
Anchors and depresses the clavicle.
Subclavius innervation
Nerve to subclavius
