A pyramidal shaped space which contains fat and many neurovascular structures. It is considered the portal to the upper limb from the neck
Axilla
The arterial supply, venous drainage, lymphatic drainage and nerve supply of the upper limb all pass through the
Axilla
The axilla contains many lymph nodes which receive drainage from the
Upper limb, anterior chest wall (including breast), back, and neck
What is the structure of the axilla?
Three walls, a apex, and a base (triangular pyramid)
The ANTERIOR wall of the axilla is composed of the
Pectoralis major and pectoralis minor
The POSTERIOR wall of the axilla is composed of the
Subscapularis, latissimus dorsi, and teres major
The MEDIAL wall of the axilla is composed of the
Serratus anterior
Formed by the bicipital groove of the humerus, where the anterior and posterior walls converge
Lateral “wall” of axilla
Attaches to the lateral lip of the groove
Pectoralis major
Attaches to the floor of the groove
Latissimus dorsi
The groove contains the tendon of the long head of the
Biceps femoris
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
Contains fat, lymph nodes, neurovascular structures, short head of biceps brachii and coracobrachialis
Axilla
The continuation of the subclavian artery (changes its name as it passes the first rib and enters this structure)
Axillary artery
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
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
The axillary artery has six branches in the axilla. The 1st part has one branch called the
Superior thoracic artery
The 2nd part of the axillary artery has two branches, called the
Thoracoacromial artery and lateral thoracic artery
The 3rd part of the axillary artery has three branches, called the
Subscapular, anterior humeral circumflex, and posterior humeral circumflex arteries
The nerve supply to the upper limb: provides the sensory and motor innervation to the upper limb
Brachial Plexus
The brachial plexus arises from nerves in the
Neck and upper thorax
The portion of the brachial plexus within the axilla consists mostly of the
Cords of the plexus
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
Connective tissue which surrounds the axillary artery and brachial plexus
-an evagination of deep fascia of the neck
Axillary sheath
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
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
In addition to receiving other deep veins within the axilla, the axillary vein receives the
Cephalic vein
The axillary vein is NOT within the axillary sheath, rather it is
Anterior to the sheath
Important clinically due to their drainage of the breast.
Also receives drainage from the upper limb, chest wall, neck and back
Axillary lymph nodes
Axillary lymph nodes drain to the subclavian lymph trunk which, on the left, drains into the
Thoracic duct
Axillary lymph nodes drain to the subclavian lymph trunk which, on the right, drains into the
Right lymphatic duct
Receive drainage from the anterior chest wall and breast
Anterior axillary lymph nodes
Receive drainage from the posterior chest wall
Posterior axillary lymph nodes
Receive drainage from the upper limb
Lateral axillary lymph nodes
The anterior, lateral, and posterior lymph nodes drain into the
Central and apical nodes
The efferent drainage from the apical nodes forms the
Subclavian trunk
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
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)
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
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
In the case of the brachial plexus, the multiple sources of nerve fibers are the anterior rami of
C5 through T1
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
The radial nerve contains nerve fibers from
C5, C6, C7, and C8
The musculotaneous nerve contains nerve fibers from
C5, C6, and C7
The median nerve contains nerve fibers from
C6,C7, C8, and T1
Begins in the neck (supraclavicular portion) and continues into the axilla (infraclaviculr portion)
Brachial plexus
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)
These divisions will then be bundled together by connective tissue into three
Cords
The lateral and medial cords contain only
Anterior division nerve fibers
The posterior cord contains only
Posterior division nerve fibers
The cords divide to give rise to the
Terminal nerves
What are three nerves that contain anterior division fibers?
Musculotaneous, median, and ulnar nerves
What are two nerves that contain posterior division fibers?
Radial and axillary nerves
Within the brachial plexus, collateral nerves arise which innervate proximal structures in the
Shoulder and axilla regions
Innervate the muscles that form the posterior wall of the axilla
The three subscapular nerves (from posterior cord)
The lateral and medial pectoral nerves (from lateral and medial cords) innervate the muscles that form the
Anterior wall of the axilla
Innervates the muscle on the medial wall of the axilla
Long thoracic Nerve
The dorsal scapular and suprascapular nerves innervate muscles of the
Shoulder girdle
Innervates all of the muscles of the anterior compartment of the arm
Musculocutaneous nerve
Innervates most of the muscles of the anterior compartment of the forearm (the remaining muscles are innervated by the ulnar nerve)
Median nerve
Innervates most of the muscles of the anterior compartment of the hand (the remaining muscles are innervated by the median nerve)
Ulnar nerve
Innervates all of the muscles of the posterior compartment of the arm and forearm
Radial nerve
Innervates only two muscles, the deltoid and teres minor
Axillary nerve
In the upper limb, the more proximal muscles are innervated by the
Higher spinal cord segments
The more distal muscles of the upper limb are innervated by
Lower spinal cord segments
The muscles of the shoulder are innervated by
C5 and C6
The muscles of the hand are innervated by
C8 and T1
This means, for example, that although the median nerve contains nerve fibers from C6 through T1, the branches of the median nerve that innervate:
- ) proximal forearm muscles
- ) distal forearm muscles
- ) hand muscles
Contain fibers from?
- ) C6 and C7
- ) C7 and C8
- ) C8 and T1
Also provide cutaneous innervation
Nerves of the brachial plexus
The most important region clinically for cutaneous innervation is the
Hand
The palmar surface of the hand receives cutaneous sensory information from the
Median and Ulnar nerves
The dorsum of the hand receives cutaneous sensory innervation from the
Radial and Ulnar nerves (w/ small contribution from median nerve)
The segmental distribution of cutaneous sensory innervation is called the
Dermatomal innervation of the limb
In general, the higher spinal cord segments provide sensory innervation to the
Lateral side of the upper limb
In general, the lower spinal cord segments provide sensory innervation to the
Medial side of the upper limb
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
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)
There are three nerves in the operative field during ALND that are susceptible to injury and deserve special note, what are they?
- ) Long thoracic nerve
- ) Thoracodorsal nerve
- ) Intercostobrachial nerve
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
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
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
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
Injury to the intercostobrachial nerve during ALND can result in
Chronic postoperative pain in region innervated
The only bony connection to the axial skeleton
Sternoclavicular Joint
Innervates proximal muscles: intrinsic shoulder muscles and axillary wall muscles
Brachial Plexus
Paralysis of muscles innervated by same terminal nerve or collateral nerve
Post-plexus lesion (injury to infraclavicular portion of plexus)
Weakness (paresis) of
muscles of same
segmental innervation
Pre-plexus lesion (Injury to supraclavicular portion)