Axilla and Brachial Plexus Flashcards Preview

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Flashcards in Axilla and Brachial Plexus Deck (87):
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A pyramidal shaped space which contains fat and many neurovascular structures. It is considered the portal to the upper limb from the neck

Axilla

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The arterial supply, venous drainage, lymphatic drainage and nerve supply of the upper limb all pass through the

Axilla

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The axilla contains many lymph nodes which receive drainage from the

Upper limb, anterior chest wall (including breast), back, and neck

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What is the structure of the axilla?

Three walls, a apex, and a base (triangular pyramid)

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The ANTERIOR wall of the axilla is composed of the

Pectoralis major and pectoralis minor

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The POSTERIOR wall of the axilla is composed of the

Subscapularis, latissimus dorsi, and teres major

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The MEDIAL wall of the axilla is composed of the

Serratus anterior

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Formed by the bicipital groove of the humerus, where the anterior and posterior walls converge

Lateral "wall" of axilla

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Attaches to the lateral lip of the groove

Pectoralis major

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Attaches to the floor of the groove

Latissimus dorsi

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The groove contains the tendon of the long head of the

Biceps femoris

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An aperture between the clavicle and the first rib which communicates between the axilla and the base of
the neck

Upper apex of the axilla

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Contains fat, lymph nodes, neurovascular structures, short head of biceps brachii and coracobrachialis

Axilla

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The continuation of the subclavian artery (changes its name as it passes the first rib and enters this structure)

Axillary artery

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The pectoralis minor muscle crosses in front of the axillary artery and divides the artery into which three parts?

1st part: proximal to the pec minor
2nd part: behind the pec minor
3rd part: distal to the pec minor

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The third part ends as the artery passes the inferior border of the teres major muscle (thus leaving the axilla and entering the arm), where it is continuous with the

Brachial Artery

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The axillary artery has six branches in the axilla. The 1st part has one branch called the

Superior thoracic artery

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The 2nd part of the axillary artery has two branches, called the

Thoracoacromial artery and lateral thoracic artery

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The 3rd part of the axillary artery has three branches, called the

Subscapular, anterior humeral circumflex, and posterior humeral circumflex arteries

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The nerve supply to the upper limb: provides the sensory and motor innervation to the upper limb

Brachial Plexus

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The brachial plexus arises from nerves in the

Neck and upper thorax

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The portion of the brachial plexus within the axilla consists mostly of the

Cords of the plexus

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The three cords surround the axillary artery and are named according to their position relative to the artery. They are called the

Lateral, medial, and posterior cords

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Connective tissue which surrounds the axillary artery and brachial plexus

-an evagination of deep fascia of the neck

Axillary sheath

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Because the axillary sheath holds the elements of the brachial plexus against the axillary artery, the nerves may be compressed by

Aneurysms of the artery

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The proximal continuation of the basilic vein which changes its name when it crosses the lower border of the teres major to enter the axilla

Axillary vein

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In addition to receiving other deep veins within the axilla, the axillary vein receives the

Cephalic vein

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The axillary vein is NOT within the axillary sheath, rather it is

Anterior to the sheath

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Important clinically due to their drainage of the breast.
Also receives drainage from the upper limb, chest wall, neck and back

Axillary lymph nodes

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Axillary lymph nodes drain to the subclavian lymph trunk which, on the left, drains into the

Thoracic duct

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Axillary lymph nodes drain to the subclavian lymph trunk which, on the right, drains into the

Right lymphatic duct

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Receive drainage from the anterior chest wall and breast

Anterior axillary lymph nodes

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Receive drainage from the posterior chest wall

Posterior axillary lymph nodes

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Receive drainage from the upper limb

Lateral axillary lymph nodes

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The anterior, lateral, and posterior lymph nodes drain into the

Central and apical nodes

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The efferent drainage from the apical nodes forms the

Subclavian trunk

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Because of this anatomy, the anterior, central, and apical axillary lymph nodes are interposed in the pathway of cancerous emboli from the breast before they reach the

Venous blood stream

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Allows for directed and accurate assessment of axillary involvement in breast cancer with minimal morbidity

-Replacing axillary lymph node dissection (ALND) as go to treatment

Sentinel lymph node biopsy (SLNB)

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A colored dye and a radioactive dye are injected into the region of the tumor and then the very few lymph nodes to which the dye drains are removed

SLNB

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A network of nerve fibers that arise from multiple sources, intermingle, and then give rise to nerves that contain nerve fibers from these multiple sources

Nerve plexus

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In the case of the brachial plexus, the multiple sources of nerve fibers are the anterior rami of

C5 through T1

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These fibers intermingle in the trunks and cords of the plexus and then give rise to nerves that contain combinations of nerve fibers from different spinal level between

C5 and T1

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The radial nerve contains nerve fibers from

C5, C6, C7, and C8

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The musculotaneous nerve contains nerve fibers from

C5, C6, and C7

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The median nerve contains nerve fibers from

C6,C7, C8, and T1

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Begins in the neck (supraclavicular portion) and continues into the axilla (infraclaviculr portion)

Brachial plexus

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As the nerve fibers pass from the neck to the axilla, they sort themselves into

Anterior and posterior divisions (distribute to anterior and posterior portions of the limb)

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These divisions will then be bundled together by connective tissue into three

Cords

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The lateral and medial cords contain only

Anterior division nerve fibers

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The posterior cord contains only

Posterior division nerve fibers

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The cords divide to give rise to the

Terminal nerves

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What are three nerves that contain anterior division fibers?

Musculotaneous, median, and ulnar nerves

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What are two nerves that contain posterior division fibers?

Radial and axillary nerves

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Within the brachial plexus, collateral nerves arise which innervate proximal structures in the

Shoulder and axilla regions

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Innervate the muscles that form the posterior wall of the axilla

The three subscapular nerves (from posterior cord)

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The lateral and medial pectoral nerves (from lateral and medial cords) innervate the muscles that form the

Anterior wall of the axilla

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Innervates the muscle on the medial wall of the axilla

Long thoracic Nerve

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The dorsal scapular and suprascapular nerves innervate muscles of the

Shoulder girdle

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Innervates all of the muscles of the anterior compartment of the arm

Musculocutaneous nerve

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Innervates most of the muscles of the anterior compartment of the forearm (the remaining muscles are innervated by the ulnar nerve)

Median nerve

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Innervates most of the muscles of the anterior compartment of the hand (the remaining muscles are innervated by the median nerve)

Ulnar nerve

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Innervates all of the muscles of the posterior compartment of the arm and forearm

Radial nerve

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Innervates only two muscles, the deltoid and teres minor

Axillary nerve

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In the upper limb, the more proximal muscles are innervated by the

Higher spinal cord segments

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The more distal muscles of the upper limb are innervated by

Lower spinal cord segments

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The muscles of the shoulder are innervated by

C5 and C6

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The muscles of the hand are innervated by

C8 and T1

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This means, for example, that although the median nerve contains nerve fibers from C6 through T1, the branches of the median nerve that innervate:
1.) proximal forearm muscles
2.) distal forearm muscles
3.) hand muscles

Contain fibers from?

1.) C6 and C7
2.) C7 and C8
3.) C8 and T1

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Also provide cutaneous innervation

Nerves of the brachial plexus

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The most important region clinically for cutaneous innervation is the

Hand

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The palmar surface of the hand receives cutaneous sensory information from the

Median and Ulnar nerves

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The dorsum of the hand receives cutaneous sensory innervation from the

Radial and Ulnar nerves (w/ small contribution from median nerve)

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The segmental distribution of cutaneous sensory innervation is called the

Dermatomal innervation of the limb

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In general, the higher spinal cord segments provide sensory innervation to the

Lateral side of the upper limb

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In general, the lower spinal cord segments provide sensory innervation to the

Medial side of the upper limb

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In general, pre-plexus nerve injuries (i.e. injuries to the spinal cord, spinal nerve, anterior rami or trunks) will result in

Dermatomal sensory losses and segmental muscular weakness

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Will result in cutaneous nerve sensory losses and muscle loss related to specific peripheral nerves (e.g. muscles innervated by the radial nerve, the median
nerve, the ulnar nerve, etc.)

Post-plexus nerve injuries (injuries to terminal or collateral nerves)

78

There are three nerves in the operative field during ALND that are susceptible to injury and deserve special note, what are they?

1.) Long thoracic nerve
2.) Thoracodorsal nerve
3.) Intercostobrachial nerve

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Arises in the neck from branches of the anterior rami of cervical vertebrae C5, C6, and C7 and innervates the important serratus anterior muscle

Long thoracic nerve

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Injury to the long thoracic nerve may paralyze the serratus anterior. Patient would then have a hard time

Raising their hand (i.e. impaired upward rotation of the scapula

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Arises from the posterior cord of the brachial plexus, passes through the axilla, and descends on the posterior wall to innervate the latissimus dorsi muscle

Thoracodorsal nerve

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Arises as a branch of the second intercostal nerve. It crosses the axilla to reach the medial side of the arm, where it provides cutaneous sensory innervations

Intercostobrachial nerve

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Injury to the intercostobrachial nerve during ALND can result in

Chronic postoperative pain in region innervated

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The only bony connection to the axial skeleton

Sternoclavicular Joint

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Innervates proximal muscles: intrinsic shoulder muscles and axillary wall muscles

Brachial Plexus

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Paralysis of muscles innervated by same terminal nerve or collateral nerve

Post-plexus lesion (injury to infraclavicular portion of plexus)

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Weakness (paresis) of
muscles of same
segmental innervation

Pre-plexus lesion (Injury to supraclavicular portion)

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