THE AXILLA (Armpit ) .. THE AXILLA (Armpit ) Isa pyramidalspacebetween the upperpart of thearm & the lateralthoracicwall.Ithas4 walls (anterior,posterior,medial & lateral ),apex&base.Theapex is pointed upward in thedirection of the root of the neck (toreceive thebrachialplexus) & communicateswith thesuperioraperture ( Inlet ofthorax)ofthorax toreceivethe axillaryartery ( continuity of subclavianartery).Theapex is known as Cervico-axillarycanal & hasbonyboundaries whichare : 1-Theclavicle anteriorly.
2-Outerborderof thefirstrib medially 3-Upper partofthe scapulaposteriorly It allows the passageof the Neuro-vascular bundle( brachialplexus & Axillaryartery)to theupperlimb . Thebase : Isformedbyskin & superficial fasciaofthe axilla,it is concavewhen the limb is besidethe trunk &becomesflat & straightonraisingand abductingthelimb due tosuspensoryligamentoftheaxilla. Theanteriorwallisformedby the clavicle, 3muscles (pectoralismajor &minorMsin addition to the subclaviusM) andtheClavi-pectoralfascia outer lip of the intertubercular groove Medial & lateral pectoral Ns
Muscle Origin Insertion Nerve supply Pectoralis Major 1-Sideofsternum (sternal) 2-Medial 2 /3 of anterior Border ofclavicle (Clavicularhead) outerlipofthe intertuberculargroove Medial & lateralpectoralNs Pectoralisminor from3rd 5thribs Neartheir costalcartilages Coracoidprocess ofscapula medial pectora Subclavius from costalcartilage of the firstrib subclaviusgroove on inferior surface ofclavicle N. to subclavius Theclavipectoralfascia: Ispart of the deep fasciaattached to the clavicle,it enclosesthe subclaviusM,then descendsdown ward deep topectoralismajor & enclosing pectoralisminorM & endsassuspensory ligamentofthe axilla.It is piercedbythefollowingstructures: 1-Lateralpectoralnerve. 2-Cephalicvein . 3-Pectoralbranch of thoracoacromialartery. 4-Somelymphaticvessels. ThelateralborderofpectoralismajorMforms theanterior foldofthe axilla.
The posterior wall of theaxilla is formedby3 muscles, thesearesubscapularis, teresmajor& latissimusdorsiMs.The posterior fold by latissimusdorsi & teresmajor Ms Subscapularistakesorigin fromthesubscapular fossa& inserts into the lessertuberosityofthehumerus.It is innervatedby upper & lower subscapularnerves ( from post.cord ). Teresmajortakes origin fromposterior surfaceoflateralborderofscapulanear the inferiorangle &is inserted in tothe mediallipof intertubercular groove.It is innervatedbythe lower subscapular nerve . Latissimusdorsitakesorigin from thefollowingsites:
A-SpinesofT 7 __T 12vertebrae. B-Thoracolumbarfascia. C-IliaccrestoftheHipbone. D-Inferiorangleofscapula Themuscle is inserted into the floorofintertubercular(Bicepital0groove & isinnervatedbythe middle subscapular ( Thoracodorsal)nerve. The medial wall is formedby the upper ribs,theirintercostalspaces& the upperpart ofserratusanteriormuscle coveringthem,which arisesfromthe outersurfacesof upper ribs& is inserted into the anterior aspectof themedial(vertebral ) borderof the scapula.It isinnervatedby the long thoracicnerve(C 5C7). The lateral wall is formedby the intertubercular ( Bicepital ) groovecontainingthe corachobrachialis M&shortheadofBiceps.. The Contents of the Axilla
1-Theaxillaryvessels: The axillaryartery,startsas thecontinuityof the subclavianartery at the outer border of thefirstrib& ends at the lowerborder ofteresmajorM( the lower limit of the axilla),where it continue as theBrachial artery.It iscrossedby thepectoralisminorM ,whichdivides it into3 parts.Thefirstpartbetween outerborder of firstrib & theupper border of pectoralisminorM( it gives a singlebranchknown as highestthoracicorsuperiorthoracicA ).The second partliesbehindpectoralisminorM& is related to the 3cords of the brachial plexus* laterally to lateral cord, medialy to medialcord & posteriorly to the posterior cord) ,while anteriorly it isrelated topectoralisminorM.Itgives2branches, the thoracoacromial & lateralthoracic.The thoracoacromialgives 4branches ,2 of them tobones ( acromial & clavicular) & other 2tomuscles (Deltoid & pectoralbranches).While the lateralthoracic branch descends to the side of the chest wall toaccompanythe long thoracicnerve within the substance of serratusanteriormuscle.. Thethirdpart of the axillaryartery extendsfromlowerborder ofpectoralisminortolowerborderofteresmajormuscle,whereit continues astheBrachialartery,itis relatedto the derivativesofthe3cordsofthe brachialplexus & it gives3branchesthese are subscapularis ( bifurcates into thoracodorsal &circumflexscapular branches ) ,anterior & posteriorcircumflex humeralarteries around the surgicalneck ofthehumerus. 2-TheBrachialplexus:It isformedbythe ventralrami of lower4cervicalnerves &the ventral ramusof the firstthoracic nerve.Thefirststage isrootsarrangementto form trunks ( C 5& 6thform the uppertrunk , C 7 aloneforms the middle trunk,whileC 8 &T 1 form the lower (inferior )trunk. The second stage is the splitting of eachtrunk to form anterior & posteriordivisions.
The third stage is the formation of the 3 cords by theRe-unionof these divisions.Theposteriordivisions of the3 trunks unite toform the posteriorcord,theanterior division of the upper & middle trunksunite to fornm the lateral cord,while theanterior division of inferiortrunk formsthemedialcord of thebrachialplexus. The last stage is the derivativesofeach cordasfollows:
The posteriorcord gives off: 1-Uppersubscapular. 2-Middle subscapular (Thoracodorsal ). 3-Lowersubscapular . 4-Axillary nerve. 5- Radialnerve. Theletralcordgivesthe following derivatives:
1-Lateralpectoralnerve. 2-Musculocutaneousnerve. 3-Lateralroottomediannerve. Themedialcordgives: 1-Medialpectoralnerve. 2-MedialcutaneousofArm. 3- Medialcutaneousofforearm. 4-Ulnarnerve. 5- Medialroottomediannerve. In addition to these derivatives,the uppertrunk gives 2branches suprascapular &nervetosubclaviusmuscle,whilethe rootsgives dorsal scapular&longthoracic nerve) C5-7) 3-The axillarylymphnodes which are arrangesin the followinggroups:
A-Anterior (pectoral) group,under anteriorborder of pectoralismajor M. B-Posterior ( subscapular ) group along thecourse ofsubscapularvessels. C-Centralgroup within the loose areolartissueof the base of the axilla. D-Lateral groupalong the course of the axillaryV nearbicipital groove. E-Medialgroup along the course of lateral thoracicvein. F-Apicalgroup in the apex of the axilla,itreceiveslymphaticsfrom the above groups&takesthem ( direct them ) to the deep cervical nodes in the root of theneck. THEBREAST: Is rudimentaryinmale & well developed in thefemale specially in lactating woman.It is a modified sweatgland located under the superficialfasciacovering the pectoral region& lying on the deep fascia covering pectoralismajor& part of theserratus anterior Ms.It extends from the sdeof thesternum medially to the anterior axillary fold laterally(part of it extends into the axilla as axillary tail of thebreast),while supero-inferiorly it extends from thelevel of 2nd rib to the 6th rib.The gland consists of lobes extending from the periphery of the glandto the area near the nipple.Eachlobe has its ownduct( lactiferous duct) which opens externally in tothe nipple( has about openings).The nipple is asmall conical projecting part surrounded by a lighterarea ( Areola).The breast is supplied by: 1-Pectoral branch of thoracoacromial artery.
2-Mammary branches from the lateralthoracic artery. 3-Perforating branches from the internalthoracic artery(i.e internal mammary A ). 4-Branches from intercostal arteries for thespaces 3rd-5th. RotaterCuffMuscles: are 4 in numbersurrounding the capsule of the shoulder jointto support &share in stabilizing the shoulderjoint.One of theseMs inserts into the lesser tuberosity ( Subscapularis ),the other3 areinserted into the greatertuberosity (Supraspinatous,infraspinatous & teres minormuscles) Muscle Origin Insertion Nerve supply Supraspinatous from supraspinous fossa Of the scapula into the superior facet of the greater tuberosity Suprascapular N Infraspinatous from infraspinous fossa middle facet of greater tuberosity Teres minor from posterior aspect of lateral Border of scapula just above the origin of teresmajor inferior facet of === Axillary N The muscles responsible for Abduction movement of the arm at shoulder joint are:
1-From0 18degreebySupraspinatous muscle. 2-1890 degreeby Deltoid muscle(innervated by the Axillary nerve ). 3-Beyond 90 degree & abovethe headisbyTrapezius & Serratusanteriormuscles. Themuscles attaching the limb to theback are byTrapezius,Rhomboid minor,Rhomboid major,Levaetorscapula&Latissimus dorsi. The latissimusdorsi id active duringswimming , climbing, rowing ,pulling &scratching the opposite scapular region. The Trapeziustakes origin from thefollowing sites:
a-From medial third of the superior nuchal line. b-From ligamentumnuchae. c-From the spine of C 7 vertebra d-From spines of T1 T 12 vertebrae( T =Thoracic ). The M is inserted into the front of lateral third ofthe clavicle,acromion process & upperlip of the spine of thescapula.It is innervated by the spinalroot of accessory nerve( 11th cranialnerve)whichis motor ,while proprioception sensations from C4 & C5 nerves. Levaetorscapula takes origin from transverseprocesses of upper 4 cervical vertebrae. It is inserted in the area around the superiorangle of scapula. It is innervatedbydorsalscapularnerve fromthe ventral ramus of C 5. Rhomboideusminortakes origin from thespinesof C 7 &T 1 vertebrae.
It is inserted intodorsal aspect of vertebralborder of scapula at the base of the spine. Is innervatedby dorsalscapular nerve. Rhomboideus major arisesfrom the spinesof T 2 T 5 vertebrae.It is inserted into dorsalaspect of vertebral borderbelow the base ofthe spine till inferior angle ofscapula &being innervated by dorsal scapular nerve. The last 3 Ms are known collectively asElevators of the scapula( one of them islevaetor scapula)& all the 3 has a commonnerve supply( dorsal scapular nerve) and allthe 3 has a common action i.e all of themwork in elevating the scapula. TheDeltoid M takes origin from the same areasof the insertion of the trapezius M .Thus it arisesfrom the inferior aspect of the crest of spines of scapula,acromion process& lateral third of theclavicle.The M fibers from the 3 sites of originconverted into a single tendon of insertion &being inserted into the Deltoid tuberosity( on thelateral aspect of the middle part of thehumerus).The deltoid is supplied by the Axillary nerve& its main action is flexion of arm atshoulder joint( anterior fibers),extension of thearm ( posterior fibers)& abduction of the arm atshoulder ( middle fibers) & in fact it is consideredas powerfull & main abductor M of the arm( from degree). Thus if the Axillary nerve is injured orcompressed by local haematoma due tofracture at the surgical neck of thehumerus,abduction becomes impossiblebecause of loss of innervation of the deltoid M.8-90 degree).Thus if the Axillary nerve isinjured or compressed by local haematomadue to fracture at the surgical neck of thehumerus,abduction becomes impossiblebecause of loss of innervation of the deltoid M.