The pectoral region

Question 1

Describe the origin, insertion + innervation of pectoralis major

Answer 1

Clavicular head = from anterior surface of medial clavicle
Sternocostal head = anterior sternum, upper 6 costal cartilages, aponeurosis of external oblique muscle
Insert = intertubercular sulcus of humerus
Innervation = medial + lateral pectoral nerves

Question 2

What are the actions of pectoralis major?

Answer 2

Adducts arm (when abducted @ shoulder)
Flex arm @ shoulder (from anatomical position, contraction of clavicular head)
Internal rotation of humerus @ shoulder (from external rotation

Question 3

Describe the origin, insertion, action and innervation of pectoralis minor

Answer 3

3rd-5th ribs to coracoid process
Stabilises scapula by drawing it anteroinferiorly against thoracic wall
Medial pectoral nerve

Question 4

Describe the origin, insertion, action + innervation of serratus anterior

Answer 4

Slips from lateral ribs 1-8 to costal surface of medial border of scapula
Protracts scapula/rotates scapula’s medial border anteroinferiorly = glenoid cavity rotates upwards = upper limb abducts above 90 degrees @ shoulder/holds medial border of scapula against ribcage
Long thoracic nerve

Question 5

What is winging of the scapula?

Answer 5

Long thoracic nerve damage (blunt trauma to neck/shoulder/heavy backpack = traction injury, surgical trauma with mastectomy with axillary clearance)
Medial border of scapula protrudes posteriorly as no longer held against chest wall by serratus anterior

Question 6

How can a winging of the scapula be tested for?

Answer 6

Push palm on wall = scapula lifts off underlying ribs
Hold unaffected shoulder with hand of affected limb + pull unaffected shoulder forwards = traction on affected = elevates its medial border scapula

Question 7

What 3 muscles act as accessory muscles in conditions of high metabolic demand/respiratory conditions to elevate the ribs + increase volume of the thoracic cavity?

Answer 7

Pectoralis major/minor + serratus anterior

Question 8

Describe the origin, insertion, action and innervation of coracobrachialis

Answer 8

Coracoid process to medial humeral shaft
Flexes arm @ shoulder, weak adductor
Musculocutaneous nerve

Question 9

Describe the origin, insertion, action and innervation of subclavius

Answer 9

Junction of 1st rib with costal cartilage to inferior middle 1/3rd of clavicle
Anchors + depresses clavicle
Nerve to subclavius

Question 10

Describe the origin, insertion and innervation of deltoid

Answer 10

Anterior border + upper surface of lateral 1/3rd of clavicle, acromion + spine of scapula
Inserts onto deltoid tuberosity
Axillary nerve

Question 11

What are the 3 actions of deltoid?

Answer 11

Anterior fibres = flex, medially rotate arm @ shoulder
Middle fibres = abduct arm from 15-90 degrees (supraspinatus for 1st 15 degrees)
Posterior fibres = extend, laterally rotate arm @ shoulder