Pectoral region and Axilla Flashcards
Pectoralis Major (Origin, Insertion, Nerve Suppy and Actions)
Origin: Clavicular head: medial clavicle. Sternal head: Anterior surface of sternum, Upper six costal cartilages (and aponeurosis of external oblique)
Insertion: Lateral lip of the bicupital groove of the humerous
Nerve supply: Lateral and medial pectoral nerves
Actions: Adductor and medial rotator of the humerous. Draws scapular anterio-inferiorly. Clavicular head flexes humerus.
Pectoralis Minor (Origin, Insertion, Nerve Suppy and Actions)
Origin: Third to fifth ribs, near the costochondral junction
Insertion: Coracoid process of scapula
Nerve supply: Medial pectoral nerve
Actions: Stabilises the scapula by drawing it inferiorly and anteriorly against the thoracic wall. Raises ribs in forces inspiration.
Coracobrachialis (Origin, Insertion, Nerve Suppy and Actions)
Origin: Caracoid process of scapula
Insertion: Anteromedial surface of the humerus, distal to crest of lesser tubercle
Nerve Supply: Musculocutaneous nerve
Actions: Flexes the arm at glenohumeral (shoulder) joint. Adducts humerus (weak).
Deltoid (Origin, Insertion, Nerve Suppy and Actions)
Origin: The anterior border and upper surface of the lateral third of the clavicle, acromion, spine of the scapula.
Insertion: Deltoid tuberosity of humerus
Nerve supply: Axillary nerve
Actions: Anterior fibres: flex arm at shoulder. Posterior fibres: extend arm at the shoulder. Middle fibres: major abductor of arm (from 15-90° abduction)
Serratus anterior (Origin, Insertion, Nerve Suppy and Actions)
Origin: Lateral surface of upper 8 or 9 ribs
Insertion: Costal aspect of medial border of the scapula
Nerve supply: Long thoracic nerve
Actions: Protracts (draws anteriorly) and stabilises scapula. Rotates scapula so arm can be abducted above 90°.
Axillary artery
From subclavian artery at the lateral border of the first rib.
To inferior border of teres major, where it continues as the brachial artery
Subdivided into three zones:
- First part: superior to pectoralis minor
- Second part: posterior to perctoralis minor
- Third part: Inferior to pectoralis minor
Axillary Vein
Follows the axillary artery.
Path:
- Formed by union brachial veins (paired) and basilic vein at inferior margin of teres major
- Becomes subclavian vein at lateral border of first rib.
Cephalic vein
- Dorsal venous arch of hand drains laterally into the cephalic vein.
- Crosses the anatomical snuffbox and travels laterally up the forearm.
- At the antecubital fossa connected to the basilic vein by the median cubutal vein.
- Pierces deep fascia of deltopectoral groove to join acillary vein via the clavipectoral triangle.
What are the boudaries of the axilla?
Apex: Lateral border of first rib, superior border of scapula, posterior border of clavicle.
Medial wall: Thiracic wall and serratus anterior
Lateral wall: Intertubercular sulcus (groove) of humerus
Posterior wall: Scapularis, teres major, latissismus dorsi
Anterior wall: Pectoralis major, pextoralis minor, subclavius.
Floor: Axillary fascia (between pectoralis major and latissimus dorsi).
What does the axilla contain?
- Axillary artery
- Brachial plexus
- Biceps brachii muscle
- Coracobrachialis muscle
- Acillary vein
- Lymph nodes draining upper limb, breast and parts of the chest wall.
- Long thoracic nerve - C5-C7 from roots of brachial plexus lies on the medial chest wall and supplies serratus anterior. Its location puts it at risk during axillary surgery and damage will lead to winging od the scapula.
- Thoracodorsal nerve and thracodorsal trunk - Innervate and vascularise latissimus dorsi.
- Intercostobrachial nerve - These transverse the axillary lymph nodes and are often divided during axillary surgery. They provide cutaneous sensation to the axillary skin.
How are the axillary lympph nodes arranged?
The axillary lymph nodes are arranged in six groups:
- Anterior (pectoral) group
- Posterior (subscapular) group
- Lateral group
- Central group
- Infraclavicular group
- Apical group
