Axilla

AXILLA

I. AXILLA

  A. Pyramidal-shaped area at the junction of the upper limb and chest

  B. Passageway for vessels and nerves of the limb

  C. Consists of an apex, base and 4 walls
    1. Apex - directed toward the root of the neck
      a. formed by convergence of bones in three major walls
            i. clavicle (anterior)
           ii. scapula (posterior)
          iii. first rib (medial)

      b. pass through cervicoaxillary canal

    2. Base - faces inferiorly
      a. formed by fascia and skin of the concave axilla (armpit)

    3. Walls
      a. Anterior wall: clavicle and pectoral muscles - lateral border of pectoralis major forms the anterior axillary fold

      b. Posterior wall: scapula and subscapularis m. - inferiorly the teres major + latissimus dorsi = posterior axillary fold

      c. Medial wall: ribs 1-4 and intercostal muscles covered by serratus anterior muscle

      d. Lateral wall: intertubercular groove of humerus (containing long head of biceps brachii m.)

  D. Contents of the axilla
    1. Branches of the brachial plexus => (see accompanying diagram)

    2. Axillary artery and its branches - continuous with subclavian a. medially and the brachial a. laterally

      a. First part - between medial border of pectoralis minor and 1st rib
          i. Superior (supreme) thoracic artery to ICS 1,2

      b. Second part - posterior to pectoralis minor
          i. Thoracoacromial artery (trunk)
                (a). acromial branch
                (b). deltoid branch
                (c). clavicular branch
                (d). pectoral branch

         ii. Lateral thoracic artery - br. to lateral breast

      c. Third part - from lateral pectoralis minor to teres major
          i. Subscapular artery
                (a). circumflex scapular artery - in triangular space
                (b). thoracodorsal artery – to lat. dorsi m.

         ii. Anterior circumflex humeral artery
        iii. Posterior circumflex humeral artery - in quad. space -larger

    3. Axillary vein - receives cephalic v.

    4. Axillary lymph nodes and vessels - along axillary a.
      a. Lateral group > central and apical nodes

      b. Pectoral (anterior) group > central and apical nodes
      c. Subscapular (posterior) nodes > central nodes
      d. Central > apical
      e. Apical group > subclavian lymph trunk-along first part of axillary

    5. Axillary sheath - encloses vessels and nerves - extension of cervical fascia

  E. Fascia
    1. Pectoral fascia: invests pectoralis major

    2. Clavipectoral fascia: invests pectoralis minor and subclavius mm. - costocoracoid membrane between them

    3. Suspensory ligament: clavipectoral fascia lateral to pectoralis minor

    4. Axillary fascia: forms floor of axilla - continuous with other fascial planes