AXILLA

 CHAPTER -2  AXILLA

The axilla or armpit is the route from the root of the neck to the upper limb. It is a pyramidal space between the upper part of arm and lateral thoracic wall.

Boundaries of axilla :

Apex: - is known as cervico axillary canal bounded in front by the clavicle, behind by the upper border of scapula and medially by the outer border of first rib.

 


 Base: formed by the skin, superficial fascia and axillary fascia.

Anterior wall: Pectoral muscles – Pectoralis major is superficial plane and pectoralis minor, subclavius, clavi pectoral fascia in deep plane.



Posterior wall: formed by subscapularis, latissimus dorsi and teres major.

Medial wall:

Upper 4 or 5 ribs and their intercostals muscles.

Upper part of serratus anterior muscle covered by the fascia.

Lateral Wall: Upper part of the arm

FOR BOUNDARIES AND CONTENTS OF AXILLA, WATCH THIS VIDEO:

https://youtu.be/npd-A0xtORs

Contents:

Axillary artery and its branches

Axillary vein and its tributaries

Axillary lymph nodes

Axillary fat and axillary tail of Spence

Cords of brachial plexus and their branches.



Axillary artery :

          It is the continuation of the third part of subclavian artery.

Extent : From the outer border of first rib to the lower border of teres major muscle.

Axillary sheath :

Encloses the proximal part of axillary artery and vein together with brachial plexus.

It is derived from pre vertebral layer of deep cervical fascia.

Parts of axillary artery :

          Axillary artery is divided into three parts by the pectoralis minor –

first part proximal to the muscle,

second part behind

and third part distal to the muscle.

 

 

 

Schematic – Extent of Axillary artery (AA) and its branches

Relations of axillary artery:

          The important relations of the axillary artery are the cords of the brachial plexus to the first and second parts and the branches of brachial plexus to the third part of axillary artery.

 (Note : The cords have corresponding relations to the 2nd part of axillary artery and axillary vein is medial to all the parts)

Relations of first part :

Laterally – Lateral and posterior cords of brachial plexus

Posteriorly – medial cord of brachial plexus

Medially – axillary vein

Anteriorly : Pectoral fascia, pectoralis major and clavi pectoral fascia.



Second part :

Laterally – lateral cord

Medially – medial cord, axillary vein

Posteriorly – posterior cord

Anteriorly – Pectoralis minor



Third part :

Anteriorly – medial root of median nerve crossing to join the lateral root

Laterally – median nerve and musculo cutaneous nerves

Medially – in between the Axillary artery and vein, ulnar nerve and medial cutaneous nerves of forearm lie.

Posteriorly – axillary and radial nerves


FOR AXILLARY ARTERY: ENTIRE COURSE AND RELATIONS: WATCH THESE VIDEOS:

https://youtu.be/St6Wgd8GJFc

https://youtu.be/Pxvyg7OgP6Q

Branches of axillary artery:

From the first part -         a) superior thoracic artery

From the second part       b) acromio thoracic artery

                                         c) lateral thoracic artery

From the third part           d) subscapular artery

                                         e) anterior circumflex humeral artery

                                         f) posterior circumflex humeral artery




Applied anatomy:

Axillary Arch : A muscular band occasionally extends from the latissimus dorsi to the pectoralis major which may compress the axillary vessels causing venous thrombosis.

BRACHIAL PLEXUS

There are five stages in the brachial plexus.

Root stage

Trunk stage

Division stage

Cord stage

Branches stage

Situation :

Root and trunk stages are present in the neck

Division stage is in the apex of axilla or cervico axillary canal.

Cord and branches stages are present in the axilla.

Roots: Ventral rami of lower four cervical nerves and first thoracic nerve( C5,C6,C7,C8,T1)

Prefixed type: When the C4 root joins with C5, it is prefixed. In this, T1 contribution is absent.

Post fixed type : When the L2 contribution is more with the disappearance of C4, it is called post fixed type.

Trunks : Upper middle and lower trunks are present.


 Division :  Each trunk divides into anterior and posterior divisions.

 Cords :

Anterior divisions of upper and middle trunks join to form lateral cords.

Anterior division of lower trunk continues as medial cord

Posterior divisions of upper, middle and lower trunks join to form posterior cord.

Branches :

Lateral cord gives three branches :

Lateral pectoral nerve (C5,6,7)

Musculo cutaneous nerve(C5,6,7)

Lateral root of median nerve( C5,6,7)

Medial cord gives five branches :

Medial pectoral nerve ( C8,T1)

Medial root of median nerve( C8,T1)

Medial cutaneous nerve of arm ( C8, T1)

Medial cutaneous nerve of forearm ( C8, T1)

Ulnar nerve ( C8, T1)

Posterior cord gives five branches :

Upper subscapular nerve ( C5,C6)

Lower subscapular nerve ( C5,C6)

Axillary nerve( C5,C6)

Nerve to latissimus dorsi ( C6,C7,C8)

Radial nerve ( C5,C6,C7,C8, T1)

FOR ENTIRE BRACHIAL PLEXUS, WATCH THIS VIDEO:

https://youtu.be/XU7r3hXrzcU

Erb’s Point :

          It is about 2 cm wide where 6 nerves meet

6 nerves are

C5 root

C6 root

Anterior division of upper trunk

Posterior division of upper trunk

Nerve to subclavius, supra scapular nerve →from upper trunk

Injury to the Erb’s point causes Erb’s paralysis. It may be caused by

Forceful abduction of the arm in deliveries.

Fall on outstretched hand

Erb’s Paralysis :

Features are - Police man’s tips hand

Arm is adducted and medially rotated

Elbow is extended

Forearm is pronated

Palm of the hand facing backwards

AXILLARY LYMPH NODES:

Number : 20 to 30

Drainage : from

 1) the upper limb

 2) most of the mammary gland

 3) cutaneous lymphatics from the trunk above the level of umbilicus.

They are divided into five groups

Anterior

Posterior

Lateral

Central

Apical



Anterior group :

They lie along the lateral thoracic vessels. They drain most of the lymphatics from the mammary gland.

Posterior group :

They lie along the subscapular vessels. They drain the posterior trunk as far below as the iliac crest.

Lateral group :

They lie postero medial to axillary vein receiving lymphatics from the upper limb except these following cephalic vein.

Central group :

They lie in the base of axilla receiving afferents from the above these group.

Apical group :

They are situated in the apex of axilla medial to the axillary vein. They receive afferents from all the axillary lymph nodes, and also lymphatics of the upper margin of mammary gland and also lymphatics of the upper limb following the cephalic vein.

 

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