• the pyramidal space superior to the armpit
• at the junction of the upper membrane with the thorax
• lies anterior to the scapula, lateral to the upper 4 or 5 ribs and posterior to the clavicle

• the continuity between the thoracocervical region and the upper limb
• serves as an important passageway for the nerves and vessels of the upper limb

• directed superiorly toward the root of the neck and is triangular in outline
• subclavian artery and vein and brachial plexus pass through this opening

• the inferior concavity of the armpit
• formed by the axillary fascia (anteriorly continuous with the pectoral fascia and posteriorly continuous with the fascia of Latissimus dorsi) and the skin of the axilla

• anterior axillary fold:
• formed by the lower border of P. Major

• posterior axillary fold:
• formed by the lower border of latissimus dorsi and T. major

• P major
• P minor
• subclavius
• clavipectoral fascia

• situated deep to P major and its investing fascia
• attached superiorly to the clavical, immediately splits to enclose the subclavius
• at inferior border of subclavius it fuses into a single layer where it continues until P minor, which it encloses
• blends with axillary fascia at the base of the axilla

• portion of the clavipectoral fascia that extends from the clavicle to pectoralis mminor
• it is called this because medially it is attached to the 1st rib and laterally to the coracoid process of the scapula

• cephalic vein
• thoracoacromial artery
• lateral pectoral nerve

• portion of the fascia which extends from P minor to the axillary fascia
• it is called this because it appears to hold up the axillary fascia
• it maintains the concavity of the armpit

• protecting the contents of the axilla
• raising the skin of the armpit when the clavicle is elevated
• maintaining the concavity of the armpit

• scapula
• subscapularis (on the scapula)
• Teres major
• Latissimus dorsi

• upper 4-5 ribs
• associated intercostal muscles (ICS 1-3[4])
• serratus anterior

• a thin strip of the arm (brachium) between the converging insertions of the muscles of the anterior and posterior wall of the axilla

• intertubercular groove of the humerus
• biceps brachii
• coracobrachialis

• subclavian artery
• subclavian vein
• brachial plexus
• NOTE: bounded by clavicle (subclavius), the first rib (serratus anterior), and the superior border of the scapula (subscapularis)

• The opening is called the deltopectoral triangle
• cephalic vein
• lymphatics
• branches of the thoracoacromial artery
• these structures with lateral pectoral nerve pierve the clavipectoral fascia
• opening is bounded by deltoideus, clavicle, and P. major

• The opening is called the suprascapular (scapula) notch
• suprascapular nerve
• suprascapular vessels pass superior to the suprascapular ligament

• axillary nerve
• posterior humeral circumflex artery
• bounded by T. major, subscapularis (T minor in back), long head of the Triceps brachii, and the surgical neck of the humerus

• circumflex scapular artery
• bounded by T. major, subscapularis (T minor in back), and long head of the triceps brachii

• brachial plexus (portion)
• axillary artery (and branches)
• axillary vein (and tributaries)
• axillary lymph nodes and vessels
• axillary filler (CT)

• complex of nerves which provide motor, sensory, and sympathetic innervation to the upper extremity
• plexiform arrangement allows for intermingling of nerve components from several spinal cord segments

• ventral rami of the lower four cervical spinal nerves and first thoracic spinal nerve
• C5 to T1

• 5 ventral rami (C5 to T1) are roots
• roots unite to form three trunks
• each trunk divides into an anterior and posterior division (6 total divisions)
• divisions unite to form three cords
• cords divide into 5 terminal branches

• formed from ventral rami C4-C8 instead of C5 to T1

• formed from the ventral rami of C6-T2 instead of C5 to T1

Describe the roots of the brachial plexus.

What is the location of the roots of the brachial plexus?

• derived from the ventral rami C5 to T1
• not the same as the dorsal and ventral roots which form the spinal nerves
• roots may be found between Scalenus anterior and Scalenus medius as they enter the posterior triangle of the neck

• in the posterior triangle of the neck
• they permit fibers from different roots to be mixed together

• formed by the joining of roots C5 and C6

• formed by root C7

• formed by the joining of roots C8 and T1

• located deep to the clavicle
• they sort out the fibers from the trunks destined to go to the anterior muscles (flexor compartments) of the upper member from those destined to go to the posterior muscles (extensor compartments)
• each trunk divides into an anterior and posterior division

• they maintain the sorting provided by the divisions while also permiting further mixing of the nerve fibers of the spinal nerves that contribute to the formation of the brachial plexus
• they are found in the axilla
• they give rise to terminal branches of the plexus
• 3 cords

• anterior divisions of the upper and middle trunks
• consists of fibers from C5-C7

• posterior divisions of all three trunks
• consists of C5-T1

• anterior division of the lower trunk
• consists of fibers from C8 to T1

• Dorsal Scapular Nerve
• innervates: Rhomboideus major, Rhomboideus minor, levator scapulae

• Long thoracic nerve
• innervates serratus anterior

• only the upper trunk has branches

• suprascapular nerve: supraspinatus, infraspinatus
• nerve to subclavius: subclavius

• Lateral pectoral nerve (C5,C6,C7)
• innervates pectoralis major

• Medial pectoral nerve (C8, T1)
• innervates pectoralis major and pectoralis minor

• medial brachial cutaneous nerve (C8,T1)
• provides sensory to medial arm and is joined by the intercostobrachial nerve (T2) which is the lateral cutaneous branch of the 2nd intercostal nerve
• medial antebrachial cutaneous nerve (C8, T1)
• provides sensory innervation to the medial arm

• upper subscapular nerve (C5,C6): subscapularis
• thoracodorsal (middle subscapular) nerve (C6,C7,C8): latissimus dorsi
• lower subscapular nerve (C5,C6): subscapularis, teres major

• musculocutaneous nerve (C5,C6,C7)
• Lateral root of the median nerve (C5,C6,C7)

• C5,C6,C7
• innervates muscles of the anterior compartment of the arm: biceps brachii, coracobrachialis, brachialis
• innervates skin of the lateral forearm via the lateral antebrachial cutaneous nerve

• innervates all muscles in the flexor compartment of the forearm except the 1 and 1/2 innervated by the ulnar nerve
• also innervates the first two lumbricals and muscles of the thenar eminence
• provides sensory innervation to the lateral aspect of the hand

• medial root of the median nerve (C8, T1)
• Ulnar nerve (C8, T1)

• C8,T1
• lateral root from the lateral cord and the medial root from the medial cord combine to form the median nerve
• median nerve contains fibers from C5-T1
• described in lateral root of the median nerve

• innervates flexor carpi ulnaris and ulnar half of flexor digitorum profundus in the forearm
• the 1 and 1/2 flexors of the forearm not innervated by the median nerve
• innervates muscles of the palm not supplied by the median nerve
• cutaneous innervation to the medial hand

• Axillary nerve (C5, C6)
• Radial Nerve (C5-T1)

• C5,C6
• innervates deltoideus and T minor
• cutaneous innervation of skin over the deltoid muscle via the superior lateral brachial cutaneous nerve

• C5 to T1
• innervates all extensors in the arm
• innervates all extensors in the forearm
• innervates skin over the dorsum of the arm, forearm, and lateral hand

• caused by sudden forced separation of the head from the shoulder which results in the tearing of the upper trunk proximal to the suprascapular nerve
• the result of downward traction on the shoulder during complicated delivery
• may result from a blow to the head
• also called upper trunk palsy, Erb's palsy, or Erb-Duchenne palsy

• suprascapular nerve (total)
• axillary nerve (total)
• nerve to subclavius (total)
• upper and lower subscapular nerves (total)
• lateral pectoral nerve (partial)
• musculocutaneous nerve (partial)
• median nerve (partial)
• branches of the posterior cord (partial)

• loss of infraspinatus, teres minor, supraspinatus, and deltoideus
• flexors of the arm and forearm would be weakened
• supinators of the forearm would be weakened
• you would see "Waiter's tip": the arm is rotated medially and the forearm is pronated with the hand in waiter's tip position
• sensory loss to lateral side of upper limb

• less frequent than upper plexus injury
• caused by an upward traction on the shoulder like when someone falls from a high place and grabs a structure to break the fall
• can occur during childbirth
• result from the presence of a cervical rib, tumor in apex of lung, or hypertrophied scalenus anterior
• Also called Lower Trunk Palsy, Klumpke's Paralysis, Klumpke-Dejerine Paralysis

• Ulnar Nerve (total)
• Medial Pectoral Nerve (total)
• Medial Brachial Cutaneous Nerve (total)
• Medial Anebrachial Cutaneous Nerve (total)
• Median Nerve (partial)

• injury of the lower trunk of the brachial plexus
• this is the paralysis of most of the intrinsic muscles of the hand
• also sensory loss over medial side of the upper limb

• improper use, or incorrectly fitted crutches: crutch palsy
• inferior dislocation of the head of the humerus
• falling asleep with one's arm draped over the back of a chair such that weight is applied to the axillary region (saturday night palsy)

• crutch palsy
• saturday night palsy
• Wrist drop: from radial nerve being damaged; loss of extensors of the wrist

• postganglionic sympathetic fibers
• motor innervation to blood vessels (vasomotor)
• innervation to sweat glands (sudomotor)
• innervation to arrector pili muscles (pilomotor)
• come from cervical and first 2 thoracic sympathetic ganglia

• the direct continuation of the subclavian artery
• begins at the lateral border of the first rib
• ends at the inferior border of teres major
• becomes the brachial artery

• proximal (medial) to P minor
• one branch

• posterior (deep) to P minor
• two branches

• distal (lateral) to P minor
• three branches

• the branch is the supreme (highest) thoracic artery
• passes medially over first and second ribs and intercostal spaces
• anastomoses with intercostal arteries

• Thoracoacromial artery: superior to upper border of P minor, pierces clavipectoral fascia and then divides into four branches:
• clavicular: supplies SC joint and anterior thoracic wall
• Pectoral: supplies P major, P minor, and mammary gland
• Deltoid: supplies deltoideus and P major
• Acromial: supplies acromion

• Lateral (long) thoracic artery
• passes inferiorly along anterolateral thoracic wall
• supplies serratus anterior,P major, P minor, and mammory gland

• Subscapular artery: passes posteriory and divides into two branches:
• circumflex scapular artery: runs into triangular space, participates in collateral circulation around scapula, and supplies muscles of the dorsum of scapula, T major, L dorsi, serratus anterior
• Thoracodorsal artery: supplies and runs deep to L dorsi

• anterior circumflex humeral artery: runs anterior to the humerus and supplies the biceps brachii and coracobrachialis

• Posterior circumflex humeral artery
• larger of two circumflex humeral arteries
• passes posterior to humerus in quadrangular space
• supplies shoulder joint, triceps brachii, and humerus

• begins at the lower border of T major as continuation of basilica vein
• ends at lower border of the first rib
• becomes the subclavian vein

• veins of the six branches of the axillary artery
• two venae comitantes of the brachial artery
• cephalic vein

• they receive lymph from the upper extremity, breast, thoracic wall, and deep thorax
• most common site of metastases from carcinoma of the breast
• there are 5 main groups in the axilla

• around distal portion of axillary vein
• receive lymph from upper member (except shoulder)
• first nodes involved in lymphangitis of the upper limb
• drain to central and apical axillary nodes
• 3 to 5 nodes

• 3 to 5 nodes
• around lateral thoracic artery and inferior border of P minor
• receive from anterolateral thoracic wall (including breast) and supraumbilical part of the abdominal wall
• drain to central and apical axillary nodes

• 5 to 6 nodes
• found along subscapular artery
• receive lymph from skin and muscles of: posterior thoracic wall, scapular region, and inferior part of the back of the neck
• drain to the central axillary nodes

• 4 to 5 nodes
• largest of axillary nodes
• located posterior to P minor
• receive from arm and mammary regions
• principal source of lymph is from the lateral, pectoral, and subscapular axillary nodes
• drain to apical axillary nodes

• 6 to 12 nodes
• medial to P minor, along first part of axillary artery
• near apex of axilla
• receive from all other axillary nodes
• efferents form the subclavian trunk which drains into the venous system

• a continuation of the prevertebral fascia which is carried along subclavian vessels and the brachial plexus as they pass in relation to the scalene muscles

• axillary artery
• axillary vein
• cords of the brachial plexus

• between the thyrocervical trunk and subscapular artery
• results in the reversal of blood flow in the subscapular artery so that blood can reach the third part of the axillary artery and all points distal

• anastomosis is formed by branches of the subclavian artery, axillary artery, and the aorta
• different vessels can be used to ligate an injured subclavian or axillary artery

• ligation here will severely compromise the blood flow to the upper extremity resulting in gangrene if prolonged

• transverse cervical artery (thyrocervical trunk off the subclavian)
• suprascapular artery (thyrocervical trunk off the subclavian)
• scapular circumflex artery (subscapular artery off the axillary
• posterior intercostal arteries (aorta)