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Table of Contents:-

 Notes on AXILLA  AND BRACHIAL PLEXUS

Axilla
                                    Fig.1:- Axilla
Axilla:-

INTRODUCTION:- Truncated pyramidal’space between upper part of arm and chest wall has 4 walls, apex, base.

 

Contents of The Axilla

-Axillary artery and its branches

-Axillary vein and its tributaries

-Infraclavicular part of brachial plexus

-Intercostobrachial and long thoracic nerves

-Axillary lymph nodes

-Loose areolar tissue and fat.

Axillary Artery
axillar artery
                                            Fig.2:- Axillary artery

-Arises as a continuation of the subclavian artery at the lateral border of first rib.

– Ends at the lower border of the teres major muscle to continue as the brachial artery.

-Closely related to the cords of the brachial plexus and their branches and is enclosed with them in the axillary sheath.

-The pectoralis minor divides it into three parts .

Branches of Axillary Artery

First part- One
branch:- Supreme (superior) thoracic artery; Supplies upper intercostals muscles.

Second Part -Two
branches:- Thoracoacromial artery, has clavicular, acromial, humeral and pectoral branches.
-It pierces the costocoracoid membrane(part of clavipectoral fascia.)
-Lateral thoracic artery supplies mainly the breast through lateral mammary branches.

Third Part
-Subscapular artery Largest branch:- divides into thoracodorsal and circumflex scapular arteries.

-The thoracodorsal artery accompanies the nerve and supplies latissimus dorsi.

-The circumflex scapular artery passes into the triangular space.

Posterior humeral circumflex artery runs posteriorly with axillary nerve through quadrangular space.
Anastomoses with anterior circumflex humeral artery

-Anterior humeral circumflex artery Passes anteriorly around surgical neck of humerus and anastomoses with posterior circumflex artery.

Axillary Vein
Axillary vein
                    Fig.3:Axillary Vein

 

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-Formed by the union of the venae comitantes of the brachial artery and the basilic vein

-It runs upward on the medial side of the axillary artery and ends at the lateral border of the first rib by becoming the subclavian vein.

-The vein receives tributaries, which correspond to the branches of the axillary artery, and the cephalic vein.

Axillary lymph nodes

 

lymph node of axilla
               Fig. 4:- Lymph node of Axilla

 

1.ANTERIOR: (pectoral) along medial wall with Lateral Thoracic vein

2.POSTERIOR: (Subscapular ) along medial wall with Subscapular vein

3.LATERAL: along medial side of axillary vein

4.CENTRAL: in Centre of Axillary fat, Related to Intercostobrachial N

5.APICAL: at apex of Axilla

6.INFRACLAVICULAR: on Clavipectoral fascia in deltopectoral groove

 

What is a Brachial Plexus ?
brachial plexus
                                  Fig.5:- Brachial plexus

-Brachial Plexus is a network of nerves present at the root of the neck to enter the upper limb.

-It is formed by the union of the anterior Rami of the C 5th, 6th, 7th & gth and the 1st thoracic spinal nerve.

-Brachial Plexus supplies muscles and skin of upper limb except trapezius supplied by spinal accessory nerve and an area of skin of axilla supplied by intercostobrachial nerve.

Organization of Brachial plexus

-5 Roots unite into 3 trunks in the neck:
Roots of C5 & C6 unite – Upper trunk
Root of C7 continues —Middle trunk
Roots of C8 & T1 unite – Lower trunk

-Divisions: Each trunk divides into anterior(flexor) and a posterior(extensor) division

-Cords:
Anterior divisions of the superior and middle trunks unite to form the lateral cord.
Anterior division of the inferior trunk form the medial cord.
Posterior divisions of all 3 trunks unite to form the posterior cord.

Important

-The roots lie between scalene muscles.

-The trunks in the posterior triangle.

-The divisions are behind the clavicle.

-The cords and branches are situated in axilla.


BRANCHES:-

branches
      Fig.6:- Branches of Brachial plexus
Supraclavicular branches
Supraclavicular branches
               Fig.7:- Supraclavicular branches

-The dorsal scapular nerve (C5), posterior to the roots-supplies rhomboid major,rhomboid minor and levator scapulae.

-The nerve to subclavius (C5,C6),anterior to the roots- supplies subclavius.

-The long thoracic nerve (C5,C6,C7) posterior to the roots- supplies serratus anterior.

-The suprascapular nerve (C5,C6)- supplies suppraspinatus and infraspinatus.

Branches of Lateral Cord

– lateral pectoral nerve (C5, 6, 7) pectoralis major and minor

– musculocutaneous nerve (C5, 6,7)coracobrachiais, brachialis and bicep brachii.

-lateral root of the median nerve (C5, 6, 7)

Branches of Medial cord

-Medial pectoral nerve (C8, T1)

-Medial root of the median nerve (C8, T1)

– Ulnar nerve (C7, 8, T1)

-Medial cutaneous nerve of the arm (or medial brachial cutaneous nerve; C8, T1)

-Medial cutaneous nerve of the forearm (or medial antebrachial cutaneous nerve; C8, T1)

Branches of Posterior cord

-The Upper subscapular nerve (C5, 6) -supplies subscapularis muscle.

-Thoracodorsal nerve (C5, 6, 7) -supplies latissimus dorsi

– Lower subscapular nerve (C5, 6)-supplies subscapularis and teres major.

-Axillary nerve (C5, 6)-supplies deltoid and teres minor

-Radial nerve (C5, 6, 7, 8, T1)-nerve of extensor compartment of arm and forearm.

Intercostobrachial nerve

-The lateral cutaneous branchof the second intercostal nerve does it is named the intercostobrachial nerve.

-It pierces the external intercostal and Serratus anterior, crosses the axilla to the medial side of the arm, and joins with a filament from the medial brachial cutaneous nerve.

-It supplies the skin of the upper half of the medial and posterior part of the arm.

-The intercostabrachial nerve is also sometimes divided in axillary node clearance.


APPLIED ASPECTS:-

 Erbs Palsy
Erb"s Palsy
                                   Fig.8:- Erb”s Palsy

 

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-Injury to the Upper trunk called Erb-duchenne paralysis or Erbs palsy is caused by birth injury during a breech delivery or violent displacement of head from shoulder such as from fall from motorcycle.

-Patient presents with loss of abduction, flexion and lateral rotation of arm, producing a waiter’s tip hand or porter’s hand.

The Cervical rib

-A cervical rib represents a persistent ossification of the C7 lateral costal element.

-The presence of a cervical rib can cause compression of the lower trunk of the brachial plexus or subclavian artery.

-Symptoms are weakness of the muscles around the muscles in the hand, near the base of the thumb.

– Compression of the subclavian artery is often diagnosed by finding a positive Adson’s sign on examination, where the radial pulse in the arm is lost during abduction and external rotation of the shoulder.

Klumpke”s palsy or Dejerine-Klumpke palsy
Klumpke's Palsy
          Fig.9:- Klumpke’s Palsy

 

-Lower trunk injury (C8,T1)may be caused by a difficult breech delivery, by a cervical rib or abnormal insertion of the anterior and middle scalene muscles.

Symptoms include paralysis of intrinsic hand muscles, flexors of the wrist and fingers (notably flexor carpi ulnaris and ulnar half of the flexor digitorum profundus) and C8/T1 Dermatome distribution numbness.

The patient presents with a Claw Hand.

Involvement of T1 may result in Horner’s syndrome, with ptosis, and miosis. Weakness or lack of ability to use specific muscles of the shoulder or arm.

 

Click here to Read more:-  Notes on Pectoral Region and Anatomy of Breast

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