Scapular and Pectoral Regions Flashcards
What are the muscles of the pectoral girdle also known as?
rotator cuff muscles (or assist the rotator cuff muscles)
What are the muscles of the pectoral girdle?
- deltoid muscle
- teres major muscle
- supraspinatus muscle
- infraspinatus muscle
- teres minor muscle
- subscapularis muscle
What are the rotator cuff muscles?
- supraspinatus muscle
- infraspinatus muscle
- teres minor muscle
- subscapularis muscle
What is the origin and insertion of the deltoid muscle?
- origin - lateral clavicle, acromion, and spine of scapula
- insertion - deltoid tuberosity
What is the action of the deltoid muscle?
abducts humerus (primary), flexes, extends, and rotates humerus (secondary)
What is the nerve and vascular supply of the deltoid muscle?
axillary nerve and posterior circumflex humeral vessels
What is the origin and insertion of the teres major muscle?
- origin - inferior angle of scapula
- insertion - crest of lesser tubercle of humerus
What is the action of the teres major muscle?
adducts, extends, and medially rotates humerus
What is the nerve and vascular supply of the teres major muscle?
lower subscapular nerve and subscapular vessels
What is the origin and insertion of the supraspinatus muscle?
- origin - supraspinous fossa
- insertion - greater tubercle of humerus
What is the action of the supraspinatus muscle?
abducts humerus (first 15 degrees)
What is the nerve and vascular supply of the supraspinatus muscle?
suprascapular nerve and vessels and dorsal scapular vessels
What is the origin and insertion of the infraspinatus muscle?
- origin - infraspinous fossa
- insertion - greater tubercle of the humerus
What is the action of the infraspinatus muscle?
lateral rotation of the humerus
What is the nerve and vascular supply of the infraspinatus muscle?
suprascapular nerves and vessels and subscapular vessels
What is the origin and insertion of the teres minor muscle?
- origin - lateral border of the scapula
- insertion - greater tubercle of the humerus
What is the action of the teres minor muscle?
lateral rotation of the humerus
What is the nerve and vascular supply of the teres minor muscle?
axillary nerve and suprascapular and subscapular vessels
What is the origin and insertion of the subscapularis muscle?
- origin - subscapular fossa
- insertion - lesser tubercle of humerus
What is the action of the subscapularis muscle?
medial rotation of humerus
What is the nerve and vascular supply of the subscapularis muscle?
upper and lower subscapular nerves and subscapular vessels
What protects the shoulder region by providing outer muscular support?
deltoid muscle
What protects the shoulder region by providing inner muscular support?
rotator cuff
What is the subacromial (subdeltoid) bursa?
membranous sac containing lubricating synovial fluid
Where is the subacromial (subdeltoid) bursa located?
inferior to acromion and deltoid but superior to supraspinatus muscle
True or false: The subacromial (subdeltoid) bursa communicates with the joint capsule.
(usually) FALSE.
* Note: it can become continuous with the joint capsule due to attrition of supraspinatus tendon
Explain the attrition of the supraspinatus tendon.
- tendon degenerates in middle age
- up to 25% of adults rupture tendon by age 65
- as it wears away, underlying joint capsule thins
- when capsule opens, it becomes continuous with the bursa and the person has a painful shoulder with limited arm movement
What are the 3 spaces of the shoulder region?
- quadrangular space
- triangular space
- triangular interval
What are the borders of the quadrangular space?
- superior border - teres minor muscle
- inferior border - teres major muscle
- medial border - long head of triceps brachii muscle
- lateral border - surgical neck of humerus
What are the contents of the quadrangular space?
axillary nerve and posterior circumflex humeral vessels
What are the borders of the triangular space?
- superior border - teres minor muscle
- inferior border - teres major muscle
- lateral border - long head of triceps brachii muscle
What are the contents of the triangular space?
circumflex scapular vessels
What are the borders of the triangular interval?
- superior border - teres major muscle
- medial border - long head of triceps brachii muscle
- lateral border - lateral head of the triceps brachii muscle
What are the contents of the triangular interval?
radial nerve and deep brachial artery
What is the course of the suprascapular nerve and artery? What do they supply?
- nerve - ventral rami of C5/C6; runs under superior transverse scapular ligament through the suprascapular notch
- artery - from thyrocervical trunk; runs over superior scapular ligament above suprascapular notch
- both - pass through spinoglenoid notch to infraspinatus fossa and supply supraspinatus and infraspinatus muscles
Where does the dorsal scapular nerve and artery originate and what do they supply?
- nerve - ventral ramus of C5
- artery - subclavian artery or transverse cervical artery
- both - run parallel to vertebral border of scapula and supply levator scapulae and rhomboid muscles
Where does the accessory nerve and transverse cervical artery originate and what do they supply?
- nerve - brainstem (CN XI); descends through neck and joins artery
- artery - thyrocervical trunk; runs deep to trapezius muscle
- both - supply trapezius muscle
Where does the upper and lower subscapular nerve and subscapular artery originate? What do they supply?
- nerve - posterior cord of brachial plexus (ventral rami of C5/C6)
- artery - axillary artery (splits to thoracodorsal and circumflex scapular artery)
- all - supply subscapularis muscle
- NOTE: lower subscapular nerve and subscapular artery supply teres major muscle
What would happen if there is insufficient flow through the axillary artery (temporary ligation between the thyrocervical trunk and subscapular artery)?
- blood flow in subscapular artery reverses
- allows blood to flow to upper limb
How would collateral circulation work if there was a ligation anywhere distal to the subscapular artery?
It wouldn’t. If it were distal to the subscapular artery, blood cannot flow to the upper limb.
What is the pectoral region? What is it composed of?
- region of muscle attachment between upper limb and anterior chest
- composed of pectoralis major and minor muscles
What are the two heads of the pectoralis major muscle?
clavicular and sternocostal
What envelopes the pectoralis minor?
clavipectoral fascia
What is the origin and insertion of the pectoralis major muscle?
- origin - clavicle, sternum, and ribs 2-6
- insertion - crest of greater tubercle of humerus
What is the action of the pectoralis major muscle?
adducts and medially rotates humerus
What is the nerve and vascular supply of the pectoralism major muscle?
medial and lateral pectoral nerves and thoracoacromial vessels
What is the origin and insertion of the pectoralis minor muscle?
- origin - ribs 3-5
- insertion - coracoid process of scapula
What is the action of the pectoralis minor muscle?
protracts scapula
What is the nerve and vascular supply of the pectoralis minor muscle?
medial pectoral nerve and thoracoacromial vessels
What arteries make up the arterial supply of the pectoral region?
- lateral thoracic (mammary) artery
- internal thoracic (mammary) artery
- thoracoacromial artery
What is the course of the lateral thoracic (mammary) artery?
- branch of axillary artery (deep to pectoralis minor)
- runs with long thoracic nerve
- supplies lateral thorax, lateral pectoral region, and lateral breast
What is the course of the internal thoracic (mammary) artery?
- branch of subclavian artery
- descends across interocostal spaces lateral to sternum
- supplies anterior thorax, medial pectoral region, and medial breast
What is the course of the thoracoacromial artery?
- branch of axillary artery (under pectoralis minor)
- sends off 4 branches:
- pectoral artery - supplies upper pectoral region
- clavicular artery - supplies clavicle region
- acromial artery - supplies upper shoulder region
- deltoid artery - supplies lower shoulder region
What are the nerves of the pectoral region?
- cutaneous nerves
- medial pectoral nerve
- lateral pectoral nerve
- long thoracic nerve
Describe the cutaneous nerves of the pectoral region.
- general sensory
- T1-T6
- lateral and anterior cutaneous branches of intercostal nerves
What is the course of the medial pectoral nerve?
- medial cord of the brachial plexus
- derived from ventral rami (C8-T1)
- pierces pectoralis minor to enter pectoralis major
- supplies pectoralis minor and part of pectoralis major
What is the course of the lateral pectoral nerve?
- lateral cord of the brachial plexus
- derived from ventral rami (C5-C7)
- runs above pectoralis minor to enter pectoralis major
- supplies part of pectoralis major
What is the course of the long thoracic nerve?
- derived from ventral rami (C5-C7)
- supplies serratus anterior muscle superficially
What nerve could be damaged during a mastectomy? What would this result in?
- long thoracic nerve
- winged scapula
