Pectoral region Flashcards
4 muscles of pectoral region
Pectoralis major
Pectoralis minor
Serratus anterior
Subclavius
Pectoralis major 2 heads
Sternal and Clavicular
Pectoralis major origin
Clavicular:
- Anterior surface medial clavicle
Sternocostal:
- Anterior surface of sternum
- Upper 6 costal cartilages
- Aponeurosis of external oblique muscle
Pectoralis major insertions
Intertubercular sulcus of humerus
Function and innervation of pectoralis major
- Medially rotates
- Adducts (mainly sternal head)
- Flexes the upper limb (clavicular head)
Innervation: lateral and medial pectoral nerve, branches of the lateral cord of the brachial plexus and the medial cord of the brachial plexus
Pectoralis minor origin and insertion
Origin: 3rd-5th rib
Insert: Coracoid process of scapula
Pectoralis minor function and innervation
Function:
Stabilises scapula by pulling it anteroinferiorly against thoracic wall
Innervation:
Medial pectoral nerve
Serratus anterior origin and insertion
Originates as separate ‘slips’ from the lateral aspects of ribs 1-8
Insertion: medial border of scapula
Serratus anterior function
- Protracts scapula
- Rotates medial boarder of scapula anteroinferiorly which allows the upper limb to abduct above 90 degrees at the shoulder
- Holds scapula against rib cage
Serratus anterior innervation
Long thoracic nerve
Clinical relevance long thoracic nerve
- Innervates serratus anterior which holds scapula against ribs
- If damaged, winging of scapula occurs (medial border protrudes posteriorly)
- Can be seen when pushing against wall
How can long thoracic nerve be damaged?
Trauma (to neck/shoulder)
Heavy backpack
Surgical trauma during mastectomy (stripped with axillary nodes)
What occurs when there is high metabolic demand (eg hyperventilating)?
Pectoralis major, minor and serratus anterior can act as accessory muscles of respiration by elevating ribs and allowing increased volume of thoracic cavity
Coracobrachialis importance
Identify brachial plexus
Coracobracialis O and I
O: Coracoid process scapula
I: medial side of humoral shaft (same level as deltoid tubercle)
Coracobrachialis action and innervation
Flex arm at shoulder
Weak adductor of arm
Innervation: Musculocutaneous nerve
Subclavius O and I
O: 1st rib and costal cartilage
I: Inferior surface of middle 3rd of clavicle
Subclavius Action and innervation
Action: anchors and depresses clavicle
Innervation: Nerve to subclavius
Deltoid muscle structure
Shaped like triangle (greek letter delta)
Anterior, middle and posterior parts
Deltoid O and I
O: Anterior border and upper surface of clavicle
I: Deltoid tuberosity on lateral humerus
Actions deltoid
Anterior: Flex and medially rotate arm
Middle; abduct arm from 15-90 degrees
Posterior: Extend and laterally rotate arm
Innervation deltoid
Axillary nerve
Arterial supply upper limb (proximal to distal)
Subclavian artery Axillary artery Brachial artery Radial artery Ulnar artery
(SABRU)
Axillary artery where
deep to pec minor
enters lateral border of first rib
Parts of axillary artery
1st - proximal to pectoralis minor
2nd - posterior to pectoralis minor
3rd - distal to pectoralis minor
Main branches of axillary artery
1st -
Superior thoracic
2nd -
Thoracoacromial artery,
lateral thoracic artery
3rd -
Subscapular artery
Anterior circumflex humeral
Posterior circumflex humeral
What do anterior and posterior circumflex humeral arteries form?
Anastomotic network around surgical neck of humerus
Can be damaged in fractures of this region
Axillary vein
First part receives supply from cephalic vein
Superficial veins of upper limb
Cephalic (pre axial border lateral) and Basilic (post axial border, medial)
