Editing Axilla

The pyramidal space between the upper arm and the side of the thorax, which permits the passage of the major neurovascular structures.

== '''Anatomical boundaries:''' (pyramid shape - four walls, a base and an apex) ==

* '''Floor/base:''' axillary fascia, which     extends between the four side-walls: 1) the anterior and posterior     axillary folds; and 2) the serratus anterior and the deep fascia of the     arm.
** The suspensory ligament from      the lower border of pectoralis minor attaches to the fascial floor from      above.
* '''Anterior     wall (anterior axillary fold):''' pectoralis major, pectoralis minor, subclavius,     clavipectoral fascia.
* '''Posterior     wall (posterior axillary fold):''' subscapularis and teres major, and the tendon of     latissimus dorsi.
* '''Medial wall     (chest wall):'''     upper part of serratus anterior, as far down as the fourth rib.
* '''Lateral wall     (arm):''' humerus,     coracobrachialis, biceps brachii.
* '''Apex:''' The opening between axilla     and posterior triangle of neck, between the clavicle, upper border of     scapula, outer border of first rib.
** Apex defined as      costoclavicular ligament in Sabiston


== '''Fascia''' ==

* Clavipectoral fascia
** Fascial sheet, arising from      clavicle, enclosing subclavius
** The descends to enclose      pectoralis minor
** Attaches to floor of axilla
** Passes in front of the      neurovascular structures of the axilla

== '''Contents:''' ==

=== '''Axillary     artery''' ===

** Path:
*** Commences at the outer       border of the first rib, as a continuation of the subclavian artery
*** Enters apex of axilla       behind the midpoint of the clavicle
*** Becomes the brachial artery       at the lower border of teres major
*** Enclosed within the       axillary sheath, along with cords of the brachial plexus, to which it is       closely related
*** Surface marking - a line       from the middle of the clavicle to the groove behind coracobrachialis
** Divisions:
*** A1: above pectoralis minor
*** A2: behind pectoralis minor
**** Note that this is the part        of the artery that gives the cords of the brachial plexus their names,        which are their positions relative to A2
*** A3: below pectoralis minor
** Branches:
*** A1 = 1, A2 = 2, A3 = 3.
*** SALSAP
*** A1
**** Superior thoracic artery        (supplies pec major and minor)
*** A2
**** Acromiothoracic - runs        over pec minor to pierce the clavipectoral fascia and supply four        branches (clavicular, deltoid, acromial and pectoral)
**** Lateral thoracic - runs        laterally along the lower border of pec minor to supply serratus        anterior, pec major, pec minor and female breast tissue
*** A3
**** Subscapular - largest        branch of the axilla, runs down the posterior wall of the axilla, then        divides into circumflex scapular artery and thoracodorsal artery
**** Anterior circumflex        humeral - runs deep to coracobrachialis and both heads of biceps,        passes around the neck of humerus to anastomose with the posterior        circumflex
**** Posterior circumflex        humeral - larger branch, passes through the posterior axillary wall,        supplies deltoid, triceps and shoulder joint
** Variant anatomy
*** Highly variable
*** Branches especially can       have variable origins, common trunks
*** Anomalous high division       into radial and ulnar arteries
** Surgical approach:
*** See 'arterial exposures'       under Vascular Operations

=== '''Axillary     vein''' ===

** Path:
*** Commences at lower border       of teres major as a continuation of the basilic vein and paired brachial       veins
*** Becomes subclavian vein at       the outer border of the first rib, in front of scalenus anterior
*** Lies medial to axillary       artery
*** Not contained within the       axillary sheath
*** Same divisions as the       artery, defined by relationship to pectoralis minor
**** 1: medial to pectoralis        minor
**** 2: beneath
**** 3: lateral
** Tributaries:
*** Second and third parts -       same as arterial branches
**** Axillary vein ->        subscapular vein -> thoracodorsal vein and angular vein
**** The angular vein is first        seen about 6cm below the axillary vein, and travels transversely across        the axilla at a horizontal plane at the level of the intersection of        the third intercostal space and the sternum. The angular vein        intersects with both thoracodorsal and long thoracic nerves.
*** First part - cephalic vein       enters after having pierced the clavipectoral fascia

=== '''Lymphatics     of the axilla''' ===

** Between 20 and 30 contained      in the fibrofatty axillary tissue
** Can be described as 'groups'      (anterior/pectoral, posterior/subscapular, lateral, central, apical.
** Stations
*** Level I: lateral to lateral       border of pec minor
**** External mammary,        subscapular, axillary vein groups
**** 4% of patients have arm        lymphatics merging with breast lymphatics here - higher risk of        lymphoedema
*** Level II: deep to pec       minor, as well as interpectoral nodes
*** Level III: superomedial to       the medial border of pec minor to Halsted's ligament
*** Additionally, Rotter's       nodes are found in between pec minor and pec major
*** Largest proportion of nodes       is found in levels I and II (15 to 20 nodes) while level III has an       average of four nodes
*** Sentinel node is usually a       level I, and occasionally a level II or extra-axillary, node

*

=== '''Nerves:''' ===

** Cords of the brachial plexus
*** Lateral
**** Lateral pectoral nerve
***** C5, C6
***** Crosses over axillary         artery and vein around medial border of pec major, then pierces the         clavipectoral fascia to supply pec major
***** Lies medial to the medial         pectoral nerve
**** Musculocutaneous nerve
**** Lateral root of the median        nerve
*** Medial
**** Medial pectoral nerve
***** C8, T1
***** Innervates both         pectoralis major and minor
***** Passes behind the         axillary artery, and emerges between the artery and vein
***** Lies within a         neurovascular bundle that wraps around the lateral border of the         pectoralis minor muscle (note that axillary vein is found just         cephalad and deep to the bundle)
**** Medial root of median        nerve
**** Medial cutaneous nerve of        the arm
**** Medial cutaneous nerve of        the forearm
**** Ulnar nerve
*** Posterior
**** Upper subscapular nerve
**** Thoracodorsal nerve (nerve        to latissimus dorsi)
***** C6/7/8
***** Large nerve - passes         behind the axillary artery and vein, then runs down posterior axillary         wall, crosses lower border of teres major, enters the deep surface of         latissimus dorsi
***** To identify: identify a         pair of subscapular veins on subscapularis. The more superficial one         is divided, revealing the deep subscapular vein and the adjacent         subscapular artery. The nerve is posterior to the axillary vein and         medial to the deep subscapular vein.
***** In danger in operations         in lower axilla
***** Injury leads to         difficulty climbing
**** Lower subscapular nerve
**** Axillary nerve
**** Radial nerve


== '''Nerves at risk during dissection:''' ==

=== '''Intercostobrachial''' ===

** Lateral cutaneous branch of      second intercostal nerve
** Emerges from second      intercostal space and crosses axilla, about 2cm inferior to axillary vein
** Supplies skin of axilla
** May be in contact with level      I nodes
** Thoracoepigastric vein      crosses the nerve vertically on its posterior aspect and aids in      identification
** Lateral cutaneous branch of      third intercostal space can also extend outwards into axilla sometimes

=== '''Thoracodorsal''' ===

** See above

=== '''Long     thoracic nerve''' ===

** Arises from posterior      aspects of C5, C6, C7.
** Unite into one nerve within      scalenus medius, emerges as a single trunk and passes down into axilla      (deep to serratus anterior fascia, posterior to midaxillary line)
** Usually appears from behind      axillary vein where that structure crosses the second rib
** Innervates serratus anterior      - fixes scapula to the chest wall during adduction of the shoulder and      extension of the arm
** Palsy results in winged      scapula deformity
** Usually found 8cm deep to      lateral edge of pectoralis minor
*



[[Category:Anatomy]]