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Axilla and Brachial Plexus
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91
Anatomy
Graduate
04/11/2012

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Term
Define the Axilla:
Definition
  • 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
Term
What does the axilla provide continuity and what does it serve as?
Definition
  • the continuity between the thoracocervical region and the upper limb
  • serves as an important passageway for the nerves and vessels of the upper limb
Term
What is the anterior boundary of the apex (cervicoaxillary canal)?
Definition
clavicle and subclavius
Term
What is the posterior boundary of the apex (cervicoaxillary canal)?
Definition
Scapula and subscapularis
Term
What is the medial border of the apex (cervicoaxillary canal)?
Definition
first rib and serratus anterior
Term
Define the Apex (cervicoaxillary canal) of the axilla.
Definition
  • directed superiorly toward the root of the neck and is triangular in outline
  • subclavian artery and vein and brachial plexus pass through this opening
Term
Define the base of the axilla.
Definition
  • 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
Term
What is the anterior boundary of the base of the axilla?
Definition
  • anterior axillary fold:
  • formed by the lower border of P. Major
Term
What is the posterior border of the base of the axilla?
Definition
  • posterior axillary fold:
  • formed by the lower border of latissimus dorsi and T. major
Term
What is the anterior wall of the axilla?
Definition
  • P major
  • P minor
  • subclavius
  • clavipectoral fascia
Term
Describe the attachments of the clavipectoral fascia.
Definition
  • 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
Term
What is the costocoracoid membrane?
Definition
  • 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
Term
What runs through the costocoracoid membrane?
Definition
  • cephalic vein
  • thoracoacromial artery
  • lateral pectoral nerve
Term
What is the Suspensory ligament of the axilla?
Definition
  • 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
Term
List the functions of the clavipectoral fascia.
Definition
  • protecting the contents of the axilla
  • raising the skin of the armpit when the clavicle is elevated
  • maintaining the concavity of the armpit
Term
What are the contents of the posterior wall of the axilla?
Definition
  • scapula
  • subscapularis (on the scapula)
  • Teres major
  • Latissimus dorsi
Term
What are the contents of the medial wall of the axilla?
Definition
  • upper 4-5 ribs
  • associated intercostal muscles (ICS 1-3[4])
  • serratus anterior
Term
Define the Lateral Wall all of the axilla
Definition
  • a thin strip of the arm (brachium) between the converging insertions of the muscles of the anterior and posterior wall of the axilla
Term
What are the contents of the lateral wall of the axilla?
Definition
  • intertubercular groove of the humerus
  • biceps brachii
  • coracobrachialis
Term
What structures pass through the opening of the apex of the axilla?
Definition
  • subclavian artery
  • subclavian vein
  • brachial plexus
  • NOTE: bounded by clavicle (subclavius), the first rib (serratus anterior), and the superior border of the scapula (subscapularis)
Term
What passes through the opening of the anterior wall of the axilla and what is this opening called
Definition
  • 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
Term
What passes through the opening known as the suprascapular (scapula) notch of the posterior wall of the axilla?
Definition
  • The opening is called the suprascapular (scapula) notch
  • suprascapular nerve
  • suprascapular vessels pass superior to the suprascapular ligament
Term
What passes through the opening, known as the quadrangular space, of the posterior wall of the axilla?
Definition
  • 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
Term
What passes through the opening, known as the triangular space, of the posterior wall of the axilla?
Definition
  • circumflex scapular artery
  • bounded by T. major, subscapularis (T minor in back), and long head of the triceps brachii
Term
What are the principal contents of the axilla?
Definition
  • brachial plexus (portion)
  • axillary artery (and branches)
  • axillary vein (and tributaries)
  • axillary lymph nodes and vessels
  • axillary filler (CT)
Term
Define Brachial Plexus.
Definition
  • 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
Term
What forms the brachial plexus?
Definition
  • ventral rami of the lower four cervical spinal nerves and first thoracic spinal nerve
  • C5 to T1
Term
How is the brachial plexus organized?
Definition
  • 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
Term
What is a prefixed brachial plexus?
Definition
  • formed from ventral rami C4-C8 instead of C5 to T1
Term
What is a postfixed brachial plexus?
Definition
  • formed from the ventral rami of C6-T2 instead of C5 to T1
Term

Describe the roots of the brachial plexus.

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

Definition
  • 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
Term
Where are the trunks of the brachial plexus found?
Definition
  • in the posterior triangle of the neck
  • they permit fibers from different roots to be mixed together
Term
What forms the upper (superior) trunk of the brachial plexus?
Definition
  • formed by the joining of roots C5 and C6
Term
What forms the middle trunk of the brachial plexus?
Definition
  • formed by root C7
Term
What forms the lower (inferior) trunk of the brachial plexus?
Definition
  • formed by the joining of roots C8 and T1
Term
Describe the divisions of the Brachial plexus.
Definition
  • 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
Term
Describe the cords of the brachial plexus.
Definition
  • 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
Term
What forms that lateral cord of the brachial plexus?
Definition
  • anterior divisions of the upper and middle trunks
  • consists of fibers from C5-C7
Term
What forms the posterior cord of the brachial plexus?
Definition
  • posterior divisions of all three trunks
  • consists of C5-T1
Term
What forms the medial cord of the brachial plexus?
Definition
  • anterior division of the lower trunk
  • consists of fibers from C8 to T1
Term
What branch comes off the C5 root of the brachial plexus and what does it innervate?
Definition
  • Dorsal Scapular Nerve
  • innervates: Rhomboideus major, Rhomboideus minor, levator scapulae
Term
What nerve branches off of C5,C6,C7 roots of the brachial plexus and what does it innervate?
Definition
  • Long thoracic nerve
  • innervates serratus anterior
Term
Which trunk(s) of the brachial plexus has(have) branches?
Definition
  • only the upper trunk has branches
Term
What are the two branches of the upper trunk (C5,C6) of the brachial plexus and what do they innervate?
Definition
  • suprascapular nerve: supraspinatus, infraspinatus
  • nerve to subclavius: subclavius
Term
What is the branch that arises from the lateral cord and what does it innervate?
Definition
  • Lateral pectoral nerve (C5,C6,C7)
  • innervates pectoralis major
Term
What is the muscular branch that arises from the medial cord and what does it innervate?
Definition
  • Medial pectoral nerve (C8, T1)
  • innervates pectoralis major and pectoralis minor
Term
What are the two cutaneous branches that arise from the medial cord?
Definition
  • 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
Term
What are the three branches of the posterior cord of the brachial plexus and what do they innervate?
Definition
  • upper subscapular nerve (C5,C6): subscapularis
  • thoracodorsal (middle subscapular) nerve (C6,C7,C8): latissimus dorsi
  • lower subscapular nerve (C5,C6): subscapularis, teres major
Term
What are the two terminal branches of the lateral cord of the Brachial plexus?
Definition
  • musculocutaneous nerve (C5,C6,C7)
  • Lateral root of the median nerve (C5,C6,C7)
Term
Describe the Musculocutaneous Nerve.
Definition
  • 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
Term
Describe the lateral root of the median nerve of the lateral cord of the brachial plexus.
Definition
  • 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
Term
What are the two terminal branches of the medial cord of the brachial plexus?
Definition
  • medial root of the median nerve (C8, T1)
  • Ulnar nerve (C8, T1)
Term
Describe the medial root of the median nerve of the brachial plexus.
Definition
  • 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
Term
Describe the ulnar nerve of the brachial plexus.
Definition
  • 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
Term
What are the two terminal branches of the posterior cord of the brachial plexus?
Definition
  • Axillary nerve (C5, C6)
  • Radial Nerve (C5-T1)
Term
Describe the axillary nerve of the brachial plexus.
Definition
  • C5,C6
  • innervates deltoideus and T minor
  • cutaneous innervation of skin over the deltoid muscle via the superior lateral brachial cutaneous nerve
Term
Describe the radial nerve of the brachial plexus.
Definition
  • 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
Term
Upper Plexus Injury: Describe this type of injury and list the different names for this injury.
Definition
  • 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
Term
What roots would be lost from an injury of the upper trunk?
Definition
C5 or C6
Term
If someone were to lose the C5 and C6 roots of the Brachial Plexus, what nerves would be affected?
Definition
  • 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)
Term
What would you expect to manifest from injury to the upper trunk of the brachial trunk?
Definition
  • 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
Term
Describe a lower plexus injury and list the other names for it.
Definition
  • 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
Term
What nerves are affected by a lower trunk injury of the brachial plexus?
Definition
  • Ulnar Nerve (total)
  • Medial Pectoral Nerve (total)
  • Medial Brachial Cutaneous Nerve (total)
  • Medial Anebrachial Cutaneous Nerve (total)
  • Median Nerve (partial)
Term
What type of injury would you see "claw hand" in?
Definition
  • 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
Term
What causes a posterior cord injury?
Definition
  • 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)
Term
What type of manifestations would you see in a posterior cord injury?
Definition
  • crutch palsy
  • saturday night palsy
  • Wrist drop: from radial nerve being damaged; loss of extensors of the wrist
Term
What type of (autonomic) fibers are innervating the upper extremities?
Definition
  • 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
Term
Describe the axillary artery; where it begins, where it ends, what it was, and what it becomes.
Definition
  • 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
Term
Where is the first part of the axillary artery and how many branches does it have?
Definition
  • proximal (medial) to P minor
  • one branch
Term
Where is the second part of the axillary artery and how many branches does it have?
Definition
  • posterior (deep) to P minor
  • two branches
Term
Where is the third part of the axillary artery and how many branches does it have?
Definition
  • distal (lateral) to P minor
  • three branches
Term
Describe the first part of the axillary artery.
Definition
  • the branch is the supreme (highest) thoracic artery
  • passes medially over first and second ribs and intercostal spaces
  • anastomoses with intercostal arteries
Term
Name the first branch of the second part of the axillary artery and list it's branches.
Definition
  • 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
Term
Name and describe the second branch of the second part of the axillary artery.
Definition
  • Lateral (long) thoracic artery
  • passes inferiorly along anterolateral thoracic wall
  • supplies serratus anterior,P major, P minor, and mammory gland
Term
Name and describe the first branch of the third part of the axillary artery.
Definition
  • 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
Term
Name and describe the second branch of the third part of the axillary artery.
Definition
  • anterior circumflex humeral artery: runs anterior to the humerus and supplies the biceps brachii and coracobrachialis
Term
Name and describe the third branch of the third part of the axillary artery.
Definition
  • Posterior circumflex humeral artery
  • larger of two circumflex humeral arteries
  • passes posterior to humerus in quadrangular space
  • supplies shoulder joint, triceps brachii, and humerus
Term
Where does the axillary vein begin, where does it end, and what does it become?
Definition
  • 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
Term
What are the tributaries of the axillary vein.
Definition
  • veins of the six branches of the axillary artery
  • two venae comitantes of the brachial artery
  • cephalic vein
Term
Why are the axillary lymph nodes very clinically important?
Definition
  • 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
Term
Describe the Brachial (lateral) group of lymph nodes.
Definition
  • 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
Term
Describe the pectoral (anterior) group of lymph nodes.
Definition
  • 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
Term
Describe the Subscapular (posterior) group of lymph nodes.
Definition
  • 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
Term
Describe the central group of the lymph nodes.
Definition
  • 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
Term
Describe the subclavian (apical) group of lymph nodes.
Definition
  • 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
Term
Describe the origin of the axillary sheath.
Definition
  • 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
Term
What are the contents of the axillary sheath?
Definition
  • axillary artery
  • axillary vein
  • cords of the brachial plexus
Term
Where can an injured axillary artery be ligated and what results from the ligation?
Definition
  • 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
Term
Why is the collateral circulation of the scapula so important?
Definition
  • 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
Term
Why is it a bad idea to ligate the axillary artery distal to the subscapular artery and proximal to the profunda brachii artery of the brachial artery?
Definition
  • ligation here will severely compromise the blood flow to the upper extremity resulting in gangrene if prolonged
Term
What are the major arteries of the collateral circulation of the scapula?
Definition
  • 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)
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