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THE AXILLA (Arm pit ) Is a pyramidal space between the upper part of the arm & the lateral thoracic wall.It has 4 walls (anterior,posterior,medial & lateral ), apex & base.The apex is pointed upward in the direction of the root of the neck (to receive the brachial plexus) & communicates with the superior aperture ( Inlet of thorax) of thorax to receive the axillary artery ( continuity of subclavian artery).The apex is known as Cervico-axillary canal & has bony boundaries which are :
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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.