Muscles of the Pectoral Girdle Flashcards
trapezius
- function is to stabilize and move the scapula
- a large superficial back muscle that resembles a trapezoid. It extends from the occipital bone to the lower thoracic vertebrae and laterally to the spine of the scapula
Action:
Superior fibers: Elevate and superiorly rotate scapula
Middle fibers: Retract scapula
Inferior fibers: Depress scapula
innervation: Accessory nerve (CN XI)
blood supply: dorsal scapular artery
deltoid
- on the lateral aspect of the shoulder.
- This muscle wraps around the shoulder superiorly and comes together at a common insertion point on the humerus
- the orientation of the fibers changes as it wraps around the shoulder from anterior to posterior. This is why the functions of the posterior, middle, and anterior fibers of the deltoid differ from each other.
Action:
- Anterior fibers: Flex and medially rotate GH joint
- Middle fibers: GH abduction
- Posterior fibers: Extend and laterally rotate GH Joint
insertion: Deltoid tuberosity of humerus
Innervation: Axillary nerve
blood supply: posterior circumflex humeral artery
teres major
- just inferior to teres minor
- runs to insert on the anterior aspect of the humerus. (This is important to appreciate to understand how it contribute to internal rotation of the glenohumeral joint)
Action: Extends, adducts, and medially rotates GH joint
Origin: Inferior lateral border and inferior angle of scapula
insertion: Lesser tubercle and intertubercular groove of humerus
Innervation: Lower subscapular nerve
blood supply: circumflex scapular artery
latissimus dorsi
- just inferior to teres major
- fans out over the back region, with fibers merging near its insertion at the intertubercular groove of the humerus
- runs to insert on the anterior aspect of the humerus. (This is important to appreciate to understand how it contribute to internal rotation of the glenohumeral joint)
Action: Extends, adducts & medially rotates GH joint (“swimmer’s muscle”)
insertion: Intertubercular groove of humerus
Innervation: Thoracodorsal nerve
blood supply: thoracodorsal artery
levator scapulae
is the most superior of rhomboid major, rhomboid minor, and levator scapulae.
Action: Elevates and inferiorly rotates scapula
Insertion: Superior medial border of scapula
Innervation: Dorsal scapular nerve
blood supply: dorsal scapular artery
rhomboid minor
is thinner and located between the rhomboid major and the levator scapulae
Action: Elevates, retracts and inferiorly rotates scapula
Insertion: Superior medial border of scapula
Innervation: Dorsal scapular nerve
blood supply: dorsal scapular artery
rhomboid major
- is larger and inferior to the rhomboid minor
Action: Elevates, retracts, and inferiorly rotates scapula
Insertion: Medial border of scapula
Innervation: Dorsal scapular nerve
blood supply: dorsal scapular artery
triceps brachii as it acts on the Glenohumeral Joint
The long head is superficial and in the middle, and this is the only portion of the triceps brachii that crosses the glenohumeral joint
Action: Extends GH joint
Origin: (long head) Infraglenoid tubercle
insertion: Olecranon process
Innervation: Radial nerve
blood supply: deep brachial artery
biceps brachii as it acts on the Glenohumeral Joint
This muscle has two heads.
- this is just medial to the Brachialis
Action: Flexes GH joint
Origin:
long head: Supraglenoid tubercle
short head: coracoid process of the scapula
insertion: Radial tuberosity and bicipital aponeurosis
Innervation: Musculocutaneous nerve
subscapularis
- On the anterior aspect of the scapula
- sits in the subscapular fossa
Action: Medially rotates GH joint,
Stabilizes the GH joint
Origin:Subscapular fossa
insertion: Lesser tubercle of humerus
Innervation: Upper and lower subscapular nerves
blood supply: subscapular artery
supraspinatus
- in the supraspinous fossa, just superior to the scapular spine
- located on the posterior aspect of the scapula
Action: Abducts GH joint, Stabilizes the GH joint
Origin:Supraspinous fossa
insertion: Greater tubercle of humerus
Innervation: Suprascapular nerve
blood supply: suprascapular artery
teres minor
- Just inferior to the infraspinatus
- located on the posterior aspect of the scapula
Action: Adducts & laterally rotates GH joint,
Stabilize the GH joint
Origin:Superior lateral border of scapula
insertion: Greater tubercle of humerus
Innervation: Axillary nerve
blood supply: circumflex scapular artery
infraspinatus
- Inferior to the scapular spine in the infraspinous fossa
- located on the posterior aspect of the scapula
Action: Adducts & laterally rotates GH joint,
Stabilize the GH joint
Origin:Infraspinous fossa
insertion: Greater tubercle of humerus
Innervation: Suprascapular nerve
blood supply: suprascapular artery
what are the rotator cuff muscles
subscapularis
supraspinatus
infraspinatus
teres minor
The teres minor, infraspinatus, and supraspinatus are all located on the posterior aspect of the scapula. They all insert onto the greater tubercle of the humerus.
the subscapularis sits on the anterior aspect of the scapula, and it sits in the subscapular fossa
serratus anterior
- on the anterior aspect of the scapula running from the thoracic wall to the medial border of the scapula
Action: Protracts and superiorly rotates scapula; stabilizes scapula
insertion: Anterior medial border of scapula
Innervation: Long thoracic nerve
blood supply: lateral thoracic artery, thoracodorsal artery
