anatomy of thoracic wall

7/25/2019 Anatomy of Thoracic Wall

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Anatomy of thoracic wall


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Topographic Anatomy of the Thorax


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Bones of Thoracic wall


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ribs 1-7"true" ribs - thosewhich attach directly to thesternum true ribs actuallyattach to the sternum bymeans of a costal cartilageand a true synovial joint.

rib 8-10"false" ribs theyarticulate via costal cartilageswith the costal cartilage of rib7.

rib 11-12"oating" ribs theanterior ends of these ribs donot articulate with the

sternum or the costalcartilage of the rib above;their costal cartilages areshort and end in the muscleof the osterolateralabdominal wall.


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Rib ribs have many

features in common! ead# osteromedial end

of the rib# it articulateswith demifacets of twoadjacent vertebralbodies.

$ec%# the constrictedregion lateral to the headof the rib# the nec% of therib is located betweenthe head and thetubercle.

Tubercle# a rojectionlocated osteroinferiorand lateral to the nec% ofthe rib# it articulates withthe transverse rocess ofa vertebra.


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body.# the shaft of the rib#the body is the longestart of a tyical rib.

Angle# the mar%edangulation of the bodylocated just lateral to the

tubercle #the angle of therib is its most osteriorart.

costal groove# the grooveon the inner surface of theinferior border of the bodyof the rib# it

accommodates theintercostal neurovascularbundle; the costal grooverovides a rotectivefunction for the intercostalneurovascular bundle#


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&ternum

the broad at bone formingthe anterior thoracic wall itis formed by three arts!manubrium# body# 'ihoidrocess. manubrium the suerior art

of the sternum# manubriummeans "handle"# as in thehandle of a sword.

jugular (surasternal) notch anotch on the suerior borderof the manubrium# it islocated between the clavicularnotches which articulate with

the sternal ends of theclavicles. clavicular notch a notch on

the suerolateral border of themanubrium# it articulate withthe sternal end of the clavicle.


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sternal angle the junction ofthe manubrium and body ofthe sternum# it is an anteriorrojection located at the levelof the costal cartilage of rib *;an imortant landmar% forinternal thoracic anatomy.

body the middle art of thesternum# it articulates with themanubrium sueriorly and the'ihoid rocess inferiorly;laterally it articulates with thecostal

'ihoid rocess the inferior

art of the sternum# 'ihoidmeans "sword shaed"; it isvariable in si+e# shae ,ossication; it articulates withthe body of the sternumsueriorly cartilages of ribs *-7.


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Muscles of the ThoracicWall

The muscles of the thoracic and abdominalwalls are in general arranged in e'ternal#middle# and internal layers.

n the thora' # these are the

(/) e'ternal intercostal muscles# (*) internal intercostal muscles# and (0) innermost intercostal muscles# subcostal

muscles# and transversus thoracis.

The internal layer and the thoracic s%eleton are

searated from the costal leura by theendothoracic fascia.

The diahragm searates the thoracic andabdominal viscera.


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The external intercostalmuscles

The e'ternal intercostal muscles

are attached to the lowermargins of ribs / to //. Their bers ass inferior and

anterior to insert on the uermargin of the rib below.

Anteriorly# at the costochondraljunctions# the e'ternal intercostalmuscles are relaced by thee'ternal intercostal membranes .

The muscles are sulied by thecorresonding intercostal nerves.

They elevate the ribs and henceare considered to be muscles ofinsiration.

They are assisted osteriorly by

the levatores costarum# whichrun from the transverserocesses to the bac%s of thesubjacent ribs and are suliedby rimary dorsal rami.


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The internal intercostalmuscles

The internal intercostal musclesare attached to the lowermargins of the ribs and costalcartilages and to the oor of thecostal groove.

Their bers ass inferior andosterior to insert on the uermargin of the rib and costalcartilage below.

1osteriorly# at the angles of theribs# the internal intercostalmuscles are relaced by the

internal intercostal membranes. The muscles are sulied by the

corresonding intercostalnerves.

2or the most art# they aremuscles of e'iration.


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The innermost intercostal muscles The innermost intercostal muscles

may be regarded as those arts ofthe internal intercostal muscles thatare internal to the intercostal vesselsand nerves.

Their action is un%nown.

The subcostal muscles# which are3uite variable# arise from the ribsosteriorly and are inserted into thesecond or third rib below.

They robably elevate the ribs. The transversus thoracis (or

sternocostalis) arises from theosterior surface of the 'ihoidrocess and body of the sternum andis inserted osteriorly into severalcostal cartilages.

t aears to be e'iratory infunction.

All these muscles are sulied by thecorresonding intercostal nerves.


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The nerves# arteries# and muscles of the thoracic wall.$ote that the intercostal vessels ass behind thelongitudinally disosed structures of the osterior

mediastinum.


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The !iaphragm The diahragm# is the most

imortant muscle of resiration. t searates the thoracic and

abdominal viscera. Three of its arts (sternal#

costal# and lumbar) are insertedinto the central tendon# atrifoliate structure that liesimmediately inferior to theheart.

The sternal art consists of slisfrom the 'ihoid rocess# which(in vivo) descend to the centraltendon.

4n each side# a small ga%nown as the sternocostal

triangle is resent between thesternal and costal arts. ttransmits the suerioreigastric vessels and somelymhatics# and it may be thesite of a diahragmatic hernia.


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The costal arts# which form the right and left"domes#" arise from the inner surfaces of the lower

costal cartilages and ribs and interdigitate with thetransversus abdominis. They are inserted into the central tendon

anterolaterally. 5ach lumbar (or vertebral) art arises from (/) a

lateral arcuate ligament over the 3uadratus

lumborum# (*) a medial arcuate ligament over thesoas major# and (0) a crus from the uer lumbarvertebrae . 6sually the right crus arises from the rst to third (or

fourth) lumbar vertebrae (/ to 0 or / to 8) and the leftfrom .9.l to * or / to 0.

The crura are united anterior to the aorta by the medianarcuate ligament# a brous arch that forms the aorticoening.

The right crus slits around the esohagus# and art of itcontinues into the susensory ligament of the duodenum.

The left crus is smaller and more variable.


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The diahragm has three majoroenings. The esohageal oening in the

right crus transmits the esohagusand vagus nerves.

The aortic oening lies osterior tothe crura and transmits the aorta#the thoracic duct and greater

slanchnic nerves# and occasionallythe a+ygos vein.

The foramen for the inferior venacava# in the right half of the centraltendon# transmits the vena cava#right hrenic nerve# and lymhaticvessels.

4ther structures that ierce or

are related to the diahragminclude the slanchnic nerves#symathetic trun%# subcostalnerves and vessels# suerioreigastric and musculohrenicvessels# and a+ygos andhemia+ygos veins.


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"ntercostal ner#es

ntercostal nerves 8 to : are "tyical in that they suly only the thoracic wall and itsassociated muscles (intercostal# subcostal# serratus osterior suerior# andtransversus thoracis).

5ach asses inferior to the nec% of the corresonding rib and enters the costal groove.

At the anterior end of the intercostal sace# it asses through the internal intercostal

muscle# e'ternal intercostal membrane# and ectoralis major# to be distributed as theanterior cutaneous branch to the anterior chest.

5ach intercostal nerve gives o< a collateral branch to the inferior art of theintercostal sace and a lateral cutaneous branch to the side of the chest.

n addition to being distributed to muscle and s%in# branches are given to the arietal

leura# mammary gland# and eriosteum of the ribs.

The rst thoracic nerve divides into a suerior art# which joins the brachial le'us#

and an inferior art# which becomes the rst intercostal nerve .

The lateral cutaneous branches of intercostal nerves / to 0 contribute to the uer

limb# that of the second being %nown as the intercostobrachial nerve. ntercostal nerves 7 to // suly the abdominal as well as the thoracic wall; hence

they may be termed thoraco-abdominal.

The ventral ramus of thoracic nerve /* is %nown as the subcostal nerve. t enters the

abdomen osterior to the lateral arcuate ligament# crosses osterior to the %idney#enetrates the muscles of the abdominal wall# enters the rectus sheath# and becomes

cutaneous


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$loo! #essels an!lymphatic !rainage

The thoracic wall is sulied bybranches of (/) the subclavian artery(internal thoracic and highest intercostalarteries)# (*) the a'illary artery# and (0)the aorta (osterior intercostal andsubcostal arteries).

The internal thoracic

The internal thoracic artery (reviouslycalled the internal mammary) arteryarises from the rst art of thesubclavian artery.

t descends osterior to thesternomastoid muscle# clavicle# andsubclavian and internal jugular veins

t then descends osterior to the uersi' costal cartilages# immediately lateral

to the sternum# and anterior to theleura. t gives branches to the intercostal

saces# leura# ericardium# and breast. At the si'th intercostal sace# it divides

into the suerior eigastric andmusculohrenic arteries.


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%osterior intercostal arteries 1osterior intercostal arteries / and * arise from the highest

intercostal artery# which is a branch of the costocervicaltrun% of the subclavian artery.

1osterior intercostal arteries 0 to // arise from the aorta.

They lie osterior to the leura# a+ygos venous system# andsymathetic trun%. 5ach artery enters the costal groove# runs forward between

the vein and nerve ("9.A.$.") (between the innermost andinternal intercostals muscles)# and anastomoses withbranches of the internal thoracic or musculohrenic arteries.

A lateral cutaneous branch accomanies the corresondingnerve. The two subcostal arteries are in series with the intercostal

arteries# and they enter the abdomen with thecorresonding nerves.


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The arietal lymh nodes of the thora'are the arasternal# hrenic# andintercostal.

The arasternal nodes# situated along theuer art of the internal thoracic artery#receive lymhatics from the medial artof the breast# the intercostal saces# thecostal leura# and the diahragm anddrain into the bronchomediastinal trun%.

anatomy of thoracic wall

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