Lecture2–ThoracicWallsandBreastThoracicwall

• Themainfunctionofthethoracicwallistoprotecttheviscerawithin

• Mechanicalbasisofbreathing• Thoracicwallincludesthoraciccage(ribs,sternumand

vertebra)andcovering(skinandmuscle)ThoraciccageRibs

• Thereare12ribsandeachoftheseribsareassociatedwithacostalcartilage(anteriorly).Andthesecostalcartilagesattachtheeachoftheribstothesternumanteriorly.

• Thecostalcartilageismovablesotheyareveryimportantformobilityofthethoraciccage(allowsittoexpandinbreathing)

• Theribscanbeclassifiedviavarioussystemso True,false,floating

§ Ribs1-7=trueribs• Eachofthemattachdirectly

tothesternumviathereowncostalcartilage

§ Ribs8-10=falseribs• Eachofthemattachtothe

costalcartilageoftheribaboveit(nodirectattachmenttothesternum)

§ Ribs11-12=floatingribs• Theyhavenoanterior

attachmentatallo Typicaloratypical

§ Ribs3-9=typicalribs• Theyhaveallthesortsof

featuresthatmostoftheribshave

• Curvedandflat• Therearesomelumps

particularlyintheposteriorendthatarerelevantforarticulationwiththevertebraandforboththebodyofthevertebraandthetransverseprocesses

• Thereisagroovearoundmostoftheshaftoftheribandthisiscalledthecostalgroove.Thisgroovesheltersandprotectstheintercostalvein,arteryandnervesintheintercostalspace.

• Posteriorendo thereare2articularprocessescalledfacets.Thereisaninferiorandsuperior

facet.Thesefacetsarticulatewiththebodyofthevertebra.§ Superiorfacetarticulateswithinferiordemifacetofthebodyof

vertebraandtheinferiorfacetarticulateswiththesuperiordemifacetofthebodyofthevertebrabelow

o Thereisanarticularfacetandtuberclejustlateraltotheneck.§ Thearticularfacetisusedforthearticulationwiththetransverse

processofthevertebra.So,theheadofeachribarticulateswiththe

Netter, F.H. Interactive Atlas of Human Anatomy. 3rd ed. New Jersey, Icon Learning Systems, 2003, ISBN: 1-929007-15-9, Plate #179

Thoracic wall Protects

Mechanical basis of breathing

Includes thoracic cage and covering

Intercostal muscles

Subcutaneous fat

Skin sweat glands, fat, blood and lymphatic vessels, nerves, the mammary gland.

Pectoralis Major (superficial muscles)

Deep Fascia

Superficial fascia

Intercostal space (muscle, nerves and vessels) Rib/Thoracic cage

Ribs 11 and 12 (Floating ribs)

Have no anterior attachment

Costal cartilage

Attaches ribs to sternum anteriorly

Contributes to mobility of thoracic cage

Rib

Ribs 1-7 (True ribs)

Attach directly to sternum via costal cartilage

Ribs 8-10 (False ribs)

Attach to costal cartilage of rib above

Intercostal spaces

Author’s own

Ribs

Posterior view

Superior facet

Inferior facet Head

Neck

Tubercle Articular facet

Typical ribs (3-9)

Curved and flat Atypical ribs (1, 2, 10-12)

Different markings

Shaft

Costal groove

Inferior view

Superior view of rib 1

Angle Grooves for subclavian vessels

Scalene tubercle

Author’s own

bodyofthevertebraandthetransverseprocessarticulateswiththetransverseprocess

§ Thetubercleismadebymainlytheligamentsassociatedwiththejointsbetweentheribsandthevertebra

§ Ribs1-2,10-12=Atypicalribs• Theylookdifferenttoatypicalribduetodifferentmarkings• i.e.rib1(picture)–itisflatinthecoronalplaneunlikeotherribsthatareflat

vertically.Therearesomegroovesforthesubclavianvesselsoverthetopofthefirstrib.Thereisascalenetubercleandthisisrelevantfortheattachmentofsomeofthescalenemusclesintheneck.

• [wedon’tneedtoknowthefeaturesofalltheatypicalribs–justknowtherelationshipofthestructuresaroundtheseribsbasedonthelumpsetc.]

Sternum

• Thisiscommonlyknownasthebreastplate[check]anditclosestheanterioraspectofourribcage.

• Itismadeof3differentprocesses:o Manubrium

§ Ithasajugularnotchwhichhassomehighlyinnervatedperiosteumandskin

§ Clavicularnotch–forthearticulationoftheclavicles

§ Directlybelowtheclavicularnotchisthepointofarticulationforrib-1• Rib2articulatesatthejunctionbetweenthemanubriumandthesternum=

manubriosternaljointo Inalateralview,wecanseeabumpthatisformedbytheangleofthe

manubriumandthesternumatthisjointo ThisisknownastheangleofLouisorthesternalangleo Ifweweretoputahorizontallineallthewaythroughthethoraxwewillget

thistransverseplanethroughthesternalangleandthisiscalledtheplaneofLouis

o Bodyofsternumo Xiphoidprocess–thisislargelycartilaginousuntilmuchlaterislifewhenitstartstoossifyand

becomelesscartilaginousThoracicvertebra

• Thoracicvertebrahasmanyfeaturessimilartoothervertebrabuttheyhavesomeuniquefeatures

Articulationsforribs

• Thereisasuperiordemifacetforthearticulationwiththeribofthesamenumberasthevertebra

• Theinferiordemifacetarticulateswiththeribbelow• [note:Vertebraonehasasuperiorfacetnotademifacet

andthefullribsitshere]• Costovertebraljoint–thejointwheretheribandthe

vertebrajoins• Costotransversejoint–thejointbetweenthetransverse

processofthevertebraandtheribo Therearesomeligamentsreinforcingthisandthis

occursattheCostalfacetofthetransverseprocess

Sternum

Manubrium

Body

Xiphoid process

Clavicular notch Jugular notch

Attachment for costal cartilages

Sternal angle (of Louis)

Manubriosternal joint and attachment of 2nd costal cartilage

Author’s own

Body Vertebral canal

Pedicle

Transverse process

Lamina

Spinous process

Transverse process

Body Spinous process

Superior articular facet

Inferior articular facet

Intervertebral foramen

Intervertebral disc

Author’s own

Thoracic vertebra

Thoracic vertebrae permit mainly rotation

Head

Tubercle

Superior demifacet (head of its own rib)

Inferior demifacet

Costal facet

Rib 3

Costal facet

Costotransverse joint

Costovertebral joint

Rib

Author’s own

Articulations for ribs

Intercostalspace• Intercostalspace–spacebetweeneachoftheribs• Intercostalmuscles–musclesthatfillupthesespaces.

Intercostalmuscles

• Thereare3layersofintercostalmuscles–theyallruninthesamesortoforientation

• Themostsuperficiallayerofthemusclesiscalledtheexternalintercostalmusclesandtheyrunantero-inferiorly

o Theyprojectallthewaythroughthespaceposteriorlyandanteriorlytheyformamembranesotherearenomusclefibresanteriorly

o Theexternalintercostalmuscleselevatetheribso Theystopsomewhereatthecostochondraljunction

• Thesecondlayerofmusclesiscalledtheinternalintercostalmusclesandtheyrunperpendiculartotheexternalintercostalmuscles–postero-inferiorly

o Posteriorly,thesemusclesbreakdownandformamembranebutanteriorlywecanseeallthemusclesthroughtothesternum

o Thereare2typesofmovementsheredependingonwhereintheintercostalspace§ Ifitislateraltothecostochondraljunction–becausetheyhavetheoppositefibredirection

toexternalintercostalmuscles,theinternalintercostalmuscleswilldepresstheribs(notelevate)

§ Iftheyaremedialtothecostochondraljunction–thentheywillelevatetheribs.Thisisduetotheshapeoftheribs(3Dstructureoftheribs)

• Innermostintercostalmuscles–theytendtobebrokendownandbepatchy

o Posteriorlytheyareverydeficient–thereisnomembraneeither

o Thedirectionofthesemusclefibresarethesameasthoseoftheinternalintercostalmusclessotheybothmusthavethesamefunctions

Intercostalspace

• Intercostalveins,arteriesandnervesareinbetweentheinnermostintercostallayerandtheinternalintercostalmusclelayer.Theyareshelteredhighintheintercostalspaceunderthecostalgroovepftheribabove.

o So,ifwewanttotheaspiratesomefluidinthepleurawewanttomakesurethatwepenetrateabovetheribbelowtoavoidgoingclosetoanddamagingthisneurovascularbundle

Netter, F.H. Interactive Atlas of Human Anatomy. 3rd ed. New Jersey, Icon Learning Systems, 2003, ISBN: 1-929007-15-9, Plate #179

Intercostal muscles

Subcutaneous fat

Skin sweat glands, fat, blood and lymphatic vessels, nerves, the mammary gland.

Pectoralis Major (superficial muscles)

Deep Fascia

Superficial fascia

Intercostal space (muscle, nerves and vessels) Rib/Thoracic cage Intercostal

space

Eizenberg N, Briggs C, Barker P, Grkovic I. An@tomedia: Thorax module. Melbourne An@tomedia Publishing, 2001, ISBN: 0646 407 317

External intercostal muscles

(antero-inferior)

Internal intercostal muscles

(postero-inferior)

External intercostal membrane

Depress

Elevate

Intercostal muscles

Eizenberg N, Briggs C, Barker P, Grkovic I. An@tomedia: Thorax module. Melbourne An@tomedia Publishing, 2001, ISBN: 0646 407 317

Innermost intercostal muscle

(postero-inferior)

Deficient posteriorly

Author’s own

Intercostal vein

Intercostal artery

Intercostal nerve

Innermost intercostal muscle

Internal intercostal muscle

External intercostal muscle

Costal groove of rib

Intercostal space

Intercostalnerves• Thefigureisacoronalsection• Intercostalnervesareextensionsofthespinal

segmentalnerveswhichcomesoutoftheintervertebralforaminaofthevertebralcolumn

• Asthespinalnerveleavestheintervertebralforaminaitalsogivesoffadorsalramustosupplytheskinandmusclesoverthevertebralcolumn=erectorspinaemuscles

• Asitcomesoutlaterally,theseintercostalnervesgiveoffmuscularbranchestoalltheintercostalmuscles(inthesamesegment)andthisisimportantastheyproducemovementsoftheribsthatcontributetobreathing

• Asitgoesthroughandrunsforward,itendsupterminatingatsomecutaneousbranchesontheanteriorthoracicwallandalsosomelateralcutaneousbrancheswhichinnervatestheskinoverthelateralthoracicwall.

o Eachofthesebranchessupplyastripofskinoverthethoracicwallwhichisrelatedtothatspinalsegmentalwall.Thismakesiteasyforustodefinethedermatomesinrelativetotheintercostalspaces.(itisasinglenervehere–therearenoplexusesandthereisnomixingetc.)

• Thereare12thoracicsegments.T4=stripovernipplesandT10=stripoverbellybutton

Intercostalvessels

• Thereare2intercostalarteries–1posteriorwhichentersthespacefrombehindand1anterioronethatentersthespacefromthefront.

• Posteriorintercostalarteriesarejustsegmentalbranchesofthethoracicaorta

• Anteriorintercostalarteriesarebranchesoftheinternalthoracicarteries.Theinternalthoracicarteriesarebranchesofthesubclavianarteryandtheydescendposteriorandlateraltothesternumallthewaydownthesegmentsgivinganteriorintercostalarteriesintotheanterioraspectoftheintercostalspace.

• Anteriorandposteriorintercostalnervesanastomosewitheachothersomewhereontheanteriorthoracicwall.Thisisimportantclinicallyasitprovidesanalternaterouteforbloodtosomeoftheskinandmuscleinthisintercostalspace

o Theinternalintercostalarteriesareoftenusedforbypassesofcoronaryarteryblockages.

• Thetransversusthoracismuscleisontheinsideoftheanteriorthoracicwall.Itattachespartlytothesternumsoithasitsownname.Butithasthesamesortoffunctionsastheinnermostintercostalmuscles.

Moore K L. Clinically Oriented Anatomy. 2nd ed. Williams and Wilkins; 1985. ISBN 0683061321. Ch.1 Page 65

Intercostal nerves

Rami communicantes

Sympathetic trunk

Sympathetic ganglion

Netter, F.H. Interactive Atlas of Human Anatomy. 3rd ed. New Jersey, Icon Learning Systems, 2003, ISBN: 1-929007-15-9, Plate #179

Intercostal nerve Innermost

intercostal muscle deficient posteriorly

Netter, F.H. Interactive Atlas of Human Anatomy. 3rd ed. New Jersey, Icon Learning Systems, 2003, ISBN: 1-929007-15-9, Plate #150

T4 teets

T1O

Moore K L. Clinically Oriented Anatomy. 2nd ed. Williams and Wilkins; 1985. ISBN 0683061321. Ch.1 Page 65

Intercostal vessels

Netter, F.H. Interactive Atlas of Human Anatomy. 3rd ed. New Jersey, Icon Learning Systems, 2003, ISBN: 1-929007-15-9, Plate #179

Descending aorta Posterior intercostal artery

Internal thoracic artery

Netter, F.H. Interactive Atlas of Human Anatomy. 3rd ed. New Jersey, Icon Learning Systems, 2003, ISBN: 1-929007-15-9, Plate #176

Internal thoracic vessels

Transversus thoracis

Anterior intercostal artery