Axilla, Brachial Plexus, Subscapular Regions

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Lecture 3

• Axilla, Brachial Plexus, Subscapular Regions

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Axilla

• pyramid between arm and thorax contains
  brachial plexus, axillary vessels and lymph node

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Landmarks

• Apex entrance to axilla, passage way from neck
• superior convergence point of clavicle, scapula,
  1st rib
• Base concave inferior border fascia and skin
• Anterior border clavicle pectoral muscles
• Posterior border subscapularis, teres major,
  latissimus dorsi
• Medial border ribs, intercostal muscles,
  serratus anterior
• Lateral border humerus intertubercular groove
  (holds long head of biceps brachii)

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Axillary artery

• continuation of subclavian artery.
• segment in between 1st rib and teres major

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Segments

• A. First part of axillary artery
• between the lateral border of the 1st rib and
  medial of pectoralis minor
• inside axillary sheath, along with branch plexus
  and axillary vein
• superior thoracic artery the only branch of
  this section
• supplies 1st, 2nd intercostal spaces superior
  part of serratus anterior

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Segments

• Second part, deep to pectoralis minor
• Branches
• 1. thoracoacromial artery goes through
  clavipectoral fascia and divides deep to pect
  major into a. acromialb. clavicularc.
  deltoidd. pectoral
• 2. lateral thoracic artery to pectoral muscles
  and axillary lymph nodes esp. large in women
  provides blood to breasts

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Segments

• Third part, axillary artery from inferior edge
  of pectoralis minor to inferior edge of teres
  major
• 1. anterior humeral circumflex
• anastomoses with posterior circumflex around
  surgical neck of humerus, can also supply biceps,
  coracobrachialis
• 2. posterior humeral circumflex artery
• travels with axillary nerve through quadrangular
  space to deltoid, triceps muscles
• 3. subscapular artery
• largest branch of axillary artery along lateral
  edge of subscapularisbranches a. circumflex
  scapular - to muscles of dorsal scapulab.
  thoracodorsal - to latissimus dorsi

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Axillary Vein

• Formed by the union of basilic vein and brachial
  vein, becomes subclavian vein after 1st rib
• receives tributaries corresponding to axillary
  artery branches 
• Joined by cephalic vein superior to pectoralis
  minor

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Brachial Plexus

• Nerve network bundle from neck into axilla to arm
  (C 5, 6, 7, 8 T1)
• Nerves - progress sequentially from ventral rami
  of spinal nerves
• Rami (anterior) gt trunks gt divisions gt cords gt
  branches

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Trunk

• ventral rami - from C5-C8, T1 ( emerge between
  scalenus anterior and scalenus medius) a.
  superior(upper) trunk C5C6b. middle trunk
  C7c. inferior(lower) trunk C8T1

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Divisions

• each trunk splits to form anterior and posterior
  divisions
• a. anterior divisions - supply anterior, flexor
  of arm
• b. posterior divisions - supply posterior /
  extensors of arm

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Cords

• anterior and posterior division combine to form
  cords names refer to position relative to
  axillay artery
• a. posterior cord all 3 posterior divisions
  (superior, middle, inferior)
• b. lateral cord anterior divisions of superior,
  middle trunk
• c. medial cord anterior of inferior (lower)
  division

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Branches

• cord divide into terminal branches ( each also
  has other, side branches, below)
• a. posterior cord
• axillary nerve and radial nerve (three smaller
  branches upper, lower subscapular nerves,
  throracodorsal nerve)
• b. lateral cord
• musculocutaneous and lateral root of median nerve
  (other branch lateral pectoral nerve)
• c. medial cord
• ulnar nerve and medial root of median nerve

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Supraclavicular Branches

• Supraclavicular Branches of brachial plexus
  (from ventral rami and trunks)
• 1. dorsal scapular nerve - to rhomboideus major
  muscle, levator scapulae - from C5,C4
• 2. long thoracic nerve - to serratus anterior -
  from C5, C6, C7
• 3. nerve to the subclavius - from superior trunk,
  C5, C6 and C4
• 4. suprascapular nerve - to supra and
  infraspinatus - also from superior trunk, C5, C6
  and C4

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Infraclavicular branches

• 1.Lateral cord branches a. lateral pectoral
  nerve (side branch)
• to pectoralis major (named after lateral cord,
  actually sits medial to medial pectoral nerve )
• b. musculocutaneous (terminal) to anterior arm
  - coracobrachialis, biceps, brachials( moves
  superficial at elbow, becomes lateral
  antebrachial cutaneous nerve in forearm)
• c. Lateral root of median nerve (continuation of
  cord) join medial root to form median nerve to
  forearm flexors

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Infraclavicular branches

• 2. Medial cord branches (all from C8, T1)
• a. ulnar nerve (terminal branch) to forearm,
  hand (C8,T1, sometimes C7)
• b. medial root of median nerve (terminal branch)
  joins lateral root, forms median nerve to forearm
  flexorsc. medial pectoral nerve (side branch)
  to pectoralis minor (part of major) ( named
  after medial cord, actually sits lateral to
  lateral pectoral nerve )
• d. medial brachial cutaneous nerve (side branch)
  skin of medial arm
• e. medial antebrachial cutaneous nerve (side
  branch) skin of medial forearm

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Infraclavicular branches

• 3. Posterior cord branches to extensors, skin of
  upper limb
• a. axillary nerve (a terminal branch) to teres
  minor, deltoid (C5,C6)-- goes thru quadrangular
  space with post humeral circumflex artery, around
  neck of humerus-- ends as upper lateral brachial
  cutaneous to skin over inferior deltoid area
• b. radial nerve (terminal branch) to upper arm,
  forearm extensors and skin( triceps, anconeus,
  brachioradialis) -- goes between long and medial
  ticeps heads, sits in radial groove of humerus
  (C5-C8, T1)
• c. upper subscapualr nerve (side branch) to
  subscapularis (C5,C6)
• d. lower subscapular nerve (side branch) to
  subscapularis, teres major (C5,C6)
• e. thoracodorsal nerve (side branch) to
  latissimus dorsi(C6,C7,C8)

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