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This lecture series is brought to you guys by the University of Manchester Cardiothoracic Surgery Society andaparascopicSociety. 123These are the related PBL ILOs we will be trying to cover today. We will be par▯cularly focusing on the anatomy of the thoracic wall, intercostal spaces, the pleural cavity and linking it to the different types of pneumothoraxes 4The thorax is an irregularly shaped cylinder which contains a wall, two pleural cavities, the lungs and the mediastinum & its structures. The thorax is important for breathing, protecting vital organs and functions as a passageway for structures from one end of the body to the other. The thorax has a narrow opening, called the superior thoracic aperture, superiorly and a much larger opening inferiorly, known as the inferior thoracic aperture. 5• The superior thoracic aperture is open and continuous with the root of the neck. • The superior thoracic aperture is bounded by the manubrium of the sternum anteriorly, the medial margins of the first pair of ribs laterally and the body of the T1 vertebra posteriorly. • The first rib slopes anteriorly from its posterior attachment to the T1 vertebra to its anterior attachment with the manubrium. • The superior aspects of the pleural cavities lie on either side inside the superior aperture and extends over the first rib. 6• Major blood vessels and nerves pass in and out of the thorax at the superior thoracic aperture both anteriorly and laterally to the upper apices of the pleural cavi▯es. • Structure that pass between the upper limb and the thorax, such as the subclavian artery, vein and the brachial plexus of nerves, pass over the first rib and through the axillary inlet into the upper limb. • Each axillary inlet is formed by: • the superior margin of the scapula posteriorly, • the clavicle anteriorly, and • the lateral margin of rib I medially. • Whereas the structures that pass between the head and thorax pass more ver▯cally through the superior aperture • For example, In the midline, the trachea lies immediately anterior to the oesophagus as they pass from the neck into the thorax • The apex of each lung extends ~23cm above the first costal car▯lage into the root of the neck anteriorly, but does not extend above the neck of the first rib • Major structures pass between the neck and medias▯num in between these apices. 7• As a consequence, abnormal events in the root of the neck can involve the adjacent pleura and lung, and vice versa 7• The inferior aperture is closed off by the diaphragm, separa▯ng it from the abdominal cavity below. • The inferior thoracic aperture is bound by the vertebral body of T12 posteriorly, medial margins of 12 rib and the distal end of the 11 ribposterolaterallycostal margins of ribs 710 anterolaterally and the xiphoid process anteriorly 8Structures passing between the thorax and the abdomen either pierces or passes posteriorly to the diaphragm • The oesophagus pierces the muscular part of the diaphragm, leaving at the oesophageal hiatus • The inferior vena cava pierces thecentral tendonof the diaphragm and enter the right side of the medias▯num at theavalhiatus • the aorta passes posterior to the diaphragm. 9A ▯p for remembering the vertebral levels at which some of the important structures that pierces the diaphragm is to remember the number of le▯ers in the word. For example, • vena cava has eight le▯ers (and it pierces the diaphragm at T8) • oesophagus has ten le▯ers (and it pierces the diaphragm at T10) • and aor▯c hiatus has twelve le▯ers ( and the aorta passes posteriorly to the diaphragm at T12). 10• The thoracic wall is segmental in design and is composed of bones and muscles • The thoracic cavity is enclosed by the thoracic wall and the diaphragm into three compartments: the right and le▯ pleural cavi▯es and the medias▯num • We will be covering the sculoskeletonandneurovasculatureof the thoracic wall and the pleural cavi▯es today. • The thoracic cage is made up of the sternum, twelve pairs of ribs, twelve thoracic vertebra and their interconnec▯ng joints. 11Posteriorly, the thoracic wall is made up of twelve thoracic vertebrae and their intervertebral discs. • A typical thoracic vertebra has three sites on each side for ar▯cula▯on with ribs; two demi-facets on the vertebral body and 1 ovsh laped costal facet on the transverse process. • A typical rib consists of a curved sha▯ with anterior and posterior ends. The anterior end is con▯nuous with its costal car▯lage. The posterior end ar▯culates with the vertebral column and is characterized by a head, neck, and tubercle. • The head of a typical rib ar▯culates with the two dem -facets and forms the costovertebral joint, and the tubercle of the rib ar▯culates with the costal facet, forming costotransverse joints. • Most ribs (from rib II to IX) have three ar▯cula▯ons with the vertebral column • Although, there are excep▯ons • The first rib does not ar▯culate with the vertebra above its own, i.e. C7 • T10 (and o▯en T11) lack an inferior dem -iacet and ar▯culates only with its own ribs 12• T11 and T12 lack transverse costal facets & only ar▯culates with the heads of their own ribs 12• Laterally, the thoracic wall is formed by the 12 ribs, and three layers of flat intercostal muscles in between the ribs • All ribs articulate with the vertebral column posteriorly and terminate anteriorly in a costal cartilage. • Ribs 1-7 are known as thetrue ribsas only their costal cartilages of the articulate directly with the sternum, forming sternocostal joints. • The remaining five pairs of ribs are known asalse ribs • The costal cartilages of ribs VIII to X articulate with the inferior margins of the costal cartilages above them • Ribs 11 and 12 are calledfloating ribsbecause they do not articulate with other ribs, costal cartilages, or the sternum. 13•Anteriorly, the wall is made up by the sternum, consisting of the manubrium, body and xiphoid process. •The costal cartilages of ribs I to VII directly articulate with the sternum, whilst the costal cartilages of ribs 810 form the costal margin and indirectly articulates with the sternum. •The joint between the manubrium and body of the sternum, called the manubriosternal joint, forms the sternal angle, also called the angle of Louis. • It is easily palpable and is an important anatomical landmark 14The sternal angle is where the costal car▯lage of the second rib ar▯culates with the sternum. It is used as a reference point to count ribs during physical examina▯ons. The horizontal plane passing through the sternal angle anteriorly and the intervertebral disc between T4 and T5 is anatomically important and is a major landmark during physical examina▯ons. • separates the superior medias▯num from the inferior medias▯num • marks the posi▯on of the superior limit of the pericardium. • marks where the arch of the aorta begins and ends. • passes through the site where the superior vena cava penetrates the pericardium to enter the heart • is the level at which the trachea bifurcates, i.e. splits into right and le▯ main bronchi • marks the superior limit of the pulmonary trunk. 1516171819• A total of11 Intercostal spaceslie between adjacent ribs and are filled by intercostal muscles • Intercostal nerves, arteries and veins lie in thecostal groovealong the inferior margin of the superior rib andass in between the inner two layers of muscles. • Tip: The neurovascular intercostal arrangement can be remembered bVAN= Vein, artery and nerve. • The nerve is inferior to the artery and o▯en not protected by the groove and thus the nerve is most at risk when objects perforate the upper aspect of an intercostal space, • These vessels and nerves give outcollateral branches o▯en present just above the rib below. • The underlying parietal pleura is separated from the ribs and intercostal spaces by a layer of connec▯ve ▯ssue, called the endothoracic fascia. 20• The posterior and anterior intercostal arteries supply most of the thoracic wall. • The arterial blood supply to the thoracic wall comes from two main sources. • The thoracic aorta gives rise to posterior intercostal arteries, which supply the posterior wall • However the upper two posterior intercostal arteries actually arise from the supreme intercostal artery which is a branch of the subclavian • Subclavian arteryà costocervicaltrunkà supreme intercostal arteryà upper two posterior intercostal arteries • Remaining 9 posterior arteries are from posterior surface of thoracic aorta • the posterior intercostal arteries have branches that accompany lateral cutaneous branches of the intercostal nerves to superficial regions. • The right and le▯ internal thoracic arterie, which are major branches of the subclavian arteries in the root of the neck, travel through the through the superior thoracic aperture and along the deep aspect of the anterior thoracic wall and gives rise to the anterior intercostal arteries and these supply the anterior thoracic wall. • At the level of the sixth intercostal space, ITAs divides into two terminal branches: superior epigastric artery and musculophrenic artery. • First 6 intercostal spaces are supplied by the direct branches of ITAs, 21 whereas the last 5 are supplied by branches of the musculophrenic • Posterior and anterior intercostal vessels branch segmentally from these main arteries and pass laterally around the wall, mainly along the inferior margin of each rib • The distribu▯ons of the anterior and posterior intercostal vessels overlap and can develop anastomo▯c connec▯ons. • The anterior intercostal arteries are generally smaller than the posterior vessels. 21• Generally speaking, venous drainage from the thoracic wall parallels the pa▯ern of arterial supply • Centrally, theintercostal veinsul▯mately drain into theazygos system of veinsor into internal thoracic veins • O▯en the upper posterior intercostal veins on the le▯ side come together and form thele▯ superior intercostal vein, which emp▯es into the le▯ brachiocephalic vein. • the upper posterior intercostal veins on the right side may come together and form theright superior intercostal ve, which emp▯es into theazygos vein . • The hemiazygos and accessory hemiazygos veins rainposterior and lateral parts of the le▯ thoracic wal, pass immediately anterior to the bodies of thoracic vertebrae, andflow into the azygos vein on the right sid,e hich ul▯mately connects with thesuperior vena cava • The internal thoracic veinsdrain the anterior wall and connect with the brachiocephalic veinsin the neck. • In adults, the le▯ brachiocephalic vein crosses the midline immediately posterior to the manubrium and delivers blood from the le▯ side of the 22head and neck, the le▯ upper limb, and part of the le▯ thoracic wall into the superior vena cava. 22Very briefly, Lympha▯c vessels of the thoracic wall drain mainly into lymph nodes associated with the internal thoracic arteries, which are the arasternal nodes, with the heads and necks of ribs drained by theintercostal nodes, and with the diaphragm drain by the diaphragma▯c nodes • Parasternal nodes drain int ronchomedias▯naltrunks. • Intercostal nodes in the upper thorax also drain intoronchomedias▯naltrunks, whereas intercostal nodes in the lower thorax drain into the thoracic duct. Superficial regions of the thoracic wall drain mainly intaxillary lymph nodesin the axillaor parasternal nodes 23• The intercostal nerves innervate the thoracic wall, related parietal pleura, and associated skin. • They are the anterior rami of the twelve pairs of thoracic spinal nerves, and lie in the intercostal spaces (except T12 which isubcostal) • The posi▯on of these nerves and vessels rela▯ve to the ribs must be considered when passing objects, such ashest tubes,through the thoracic wall. • A typical intercostal nerve passes laterally around the thoracic wall in an intercostal space. • The largest of the branches is thelateral cutaneous branch, which pierces the lateral thoracic wall and divides into an anterior branch and a posterior branch that innervate the overlying skin. • The intercostal nerves end asanterior cutaneous branche, which emerge either parasternallyor lateral to the midline on the anterior abdominal wallo supply the skin. • small collateral branches can be found in the intercostal space running along the superior border of the lower rib. • In the thorax, the intercostal nerves carry: 24• Soma▯c motor innerva▯on to the muscles of the thoracic wall (intercostal, subcostal, and transversus thoracis muscles), • soma▯c sensory innerva▯on from the skin and parietal pleura • postganglionic sympathe▯c fibres to the periphery. 24• A dermatome isan area of skin in which sensory nerves derive from a single spinal nerve root • Dermatomesof the thorax generally reflect the segmental organiza▯on of the thoracic spinal nerves. • with the only excep▯on being the T1 dermatome which is located mostly on the upper limb. • The T2 dermatome, which is the highest thoracic dermatome, expands into the upper limb (intercostobrachial nerve (lateral cutaneous branch of the second intercostal nerve)). • In the midline, skin over the xiphoid process is innervated by T6. • Dermatomes of T7 to T12 follow the contour of the ribs onto the anterior abdominal wall lower intercostal nerves supply the muscles, skin, and peritoneum of the abdominal wall. • The anterosuperior region of the trunk receives branches from the anterior ramus of C4 viasupraclavicular branchesof the cervical plexus. These carry sensory 25 informa▯on of the skin overlying the upper thoracic wall. • All preganglionic nerve fibres of the sympathe▯c system are carried out of the spinal cord in spinal nerves T1 to L2 • This means that sympathe▯cfibersfound anywhere in the body ul▯mately emerge from the spinal cord as components of these spinal nerves. • Preganglionic sympathe▯cfibersdes▯ned for the head are carried out of the spinal cord in spinal nerve T1. 252627• The right and le▯ pleural cavi▯es surround the lungs and are separated from each by the medias▯num. • Each cavity is completely lined with a serous mesothelial membrane called the pleura. • Mesothelium– single layer of flat cells • As the heart extends further to the le▯, the le▯ pleural cavity is smaller. • During development, the lungs grow out of the medias▯num into their pleural cavi▯es and thus their outer surface becomes covered by pleura. • Each lung remains a▯ached to the medias▯num by a rof trmed by the airway, pulmonaryneurovasculatureand lympha▯c ▯ssues. • The pleura that lines the inner walls of the thoracic cavity is called thparietal pleura • The pleura that is reflected from the medias▯num at the pulmonary root, which covers the outer surface of each lung is called thvisceral pleura 28• The parietal pleura is thicker than the visceral pleura and can bfurther subdivided according to the part of the body it is in contact with. • Pleura related to the ribs and intercostal spaces is termed theostalpart. • Pleura covering the diaphragm is thediaphragma▯cpart. • Pleura covering the medias▯num is themedias▯nalpart. • The dome-shaped layer of parietal pleura lining the cervical extension of the pleural cavity iscervical pleura(dome of pleura or pleural cupola). • The parietal pleura is innervated by general soma▯c afferent (GSA) fibres and is very sensi▯ve to painful s▯muli • The costal pleura is innervated by branches from the intercostal nerves, and pain would be felt in rela▯on to the thoracic wall. • The diaphragma▯c pleura and the medias▯nal pleura are innervated mainly by the phrenic nerves (origina▯ng at spinal cord levels C3, C4, and C5). Pain from these areas would refer to the C3, C4, and C5 dermatomes, i.e. the lateral neck and the supraclavicular region of the shoulder. • The visceral pleura is con▯nuous with the parietal pleura at the hilum. • the visceral pleura is innervated by general visceral afferent (GVA) fibres 29 that accompany bronchial vessels • and is rela▯vely insensi▯ve to painful s▯muli. 29• Each pleural cavity is the potential space that exists between these two pleural membranes as the lung does not fully fill the pleural cavity. • They normally contain only a very thin layer of serous fluid (approximately 15 mL). As a result, the surface of the lung, which is covered by visceral pleura, freely slides over the parietal pleura. • This forms recesses, spaces in the cavity that do not contain lung, and are important for accommodating the changes in lung volume during breathing, especially forced inspiration. • These include thecosto-mediastinal andcosto-diaphragmatic recesses • The lungs do not fill this space in quiet respiration but does fill the recesses in deep breathing. • The costo-diaphragmatic recess lies inferiorly between the costal pleura wall and the diaphragmatic pleura, and is clinically important • recesses provide potential spaces in which fluids can collect and from which fluids can be aspirated. • It is shallowest after forced inspiration 30• As the pleural cavi▯es are completely separated from each other by the medias▯num, abnormal events in one pleural cavity do not necessarily affect the other cavity. This also means that the medias▯num can be entered surgically without opening the pleural cavi▯es. 30• The intercostal spaces are filled, from superficial to deep, by the external, internal and innermost intercostal muscles. • They are innervated by the related intercostal nerves • They move the ribs during inspira▯on and expira▯on • The 11 pairs of external intercostals run in an oblique anterinferior direc▯on ↘ from the lateral edges of the costal groove to the superior margins of the rib below • extending from the tubercle of the ribs to the costal car▯lages anteriorly, ending as the external intercostal membrane, a thin connec▯ve ▯ssue aponeurosis. • Most ac▯ve during inspira▯on and their contrac▯on moves the ribs superiorly • The 11 pairs of internal intercostal muscles run in an obliqueostero-inferior direc▯on ↙from the most inferior lateral edge of the costal grooves of the ribs above, to the superior margins of the ribs below, • extending from the costal car▯lages to the angle of the ribs posteriorly, ending as internal intercostal membrane at the vertebral column. • Most ac▯ve during expira▯on and moves ribs inferiorly 31• The innermost intercostals are the least dis▯nct of the three, and its fibres also run obliquely posteroinferiorly. • The neurovascular bundles of the intercostal spaces pass around the thoracic wall in the costal grooves in a plane between the innermost and internal intercostal muscles. • Innermost works with internal intercostals to depress ribs 31Addi▯onal intrinsic muscles of the thoracic wall also play a role in breathing to a lesser degree. These include subcostals, transversus thoracis,evatorescostarum, serratus posterior superior, and serratus posterior inferior muscles. Broadly speaking, they a▯ach to the ribs, their car▯lages, or thoracic vertebra–ul▯mately depressing or eleva▯ng the ribs. In addi▯on, all of the thoracic muscles provide further support and strength for the thorax. Briefly • Subcostal muscles span between the internal surface of one rib to the internal surface of the first or second rib below. • The transversus thoracis muscles lie deep to the internal thoracic vessels and secure these vessels to the wall. • The serratus posterior muscles extend obliquely from the vertebral column to the rib cage. • the serratus posterior superior muscle elevates the ribs • the serratus posterior inferior muscle depresses the ribs. • These ac▯ons are par▯cularly important in forced respira▯on. 32• Levatorescostarum • Elevates ribs in inspira▯on 32The a▯achments of the diaphragm can be divided intoeripheralandcentral a▯achments. It has three peripheral a▯achments: • Lumbar vertebrae and arcuate ligamentsligaments that span across structures of the posterior abdominal wa.ll • Costal car▯lages of ribs 710 (a▯ach directly to ribs 1112). • Xiphoid process of the sternum. The parts of the diaphragm that arise from the vertebrae are tendinous in structure, and are known as theright and le▯ crura: • Right crus– Arises from L1-L3 and their intervertebral discsSome fibres from the right crus surround the oesophageal opening, ac▯ng as a physiological sphincter to prevent reflux of gastric contents into the oesophagus. • Le▯ crus– Arises from L1-L2 and their intervertebral discs. The muscle fibres of the diaphragm arise from the margins of the inferior aperture and converge into a largecentral tendon, which fuses with the inferior surface of the fibrous pericardium. The diaphragm is not flat and balloons superiorly to the right and le▯ sides, on either side of the pericardium. The right diaphragma▯c dome is higher than the le▯, 33reaching as far as the fi▯h rib. • this is thought to be due to the presence of the liver. Branches of the ITAs(pericardiophrenic and musculophrenic) andthe superior phrenic arteries, which arise directly from lower parts of the thoracic aorta, and small branches from intercostal arteries contribute to the supply of the diaphragm superiorly. But it receives most of its supply from thi ferior phrenic arteriesinferiorly that branch directly from the abdominal aorta. • Venous drainage is mostly by parallel veins. The hemidiaphragms are innervated by the right and le▯ phrenic nervesrespec▯vely, which originates from the cervical plexus and contains fibres from C3, C4 and C5 Tip: C3,4 and 5 keeps the diaphragm alive 33341. Cervicalpleura 2. Costalpart 3. Pulmonaryligament 4. Medias▯nalpart 5. Diaphragma▯cpart 35361. Intercostalnerve 2. Intercostalartery 3. Intercostalvein 4. Collateralbranches 5. Parietalpleura 6. Endothoracicfascia 7. Costalgroove 8. Innermostintercostalmuscle 9. Internalintercostalmuscle 10. Externalintercostalmuscle 37• Joints: • Intervertebral: between vertebrae • Costovertebral: formed by the ribs and bodies of the vertebrae. • Costotransverse: formed between vertebral transverse processes and tubercle of ribs • Costochondral: costal car▯lage and rib • Sternochondral sternum and costal car▯lages • Interchondral: joining the costal car▯lages to one another • Sternoclavicular: manubrium and clavicles • Manubriosternal: manubrium and body of sternum • Xiphisternal xiphoid process and body of sternum 38• Changes in the anterior, lateral, and ver▯cal dimensions of the thoracic cavity are important for breathing. • When the muscular diaphragm contracts, the central tendon remains flat but the height of the domes decreases, and the volume of the thorax increases ver▯cally. • The intercostal muscles maintains the rigidity of the chest wall. • Changes in the anteroposterior and lateral dimensions result from eleva▯on and depression of the ribs 39• A rib’s posterior attachment to the spine is superior to its anterior attachment to the sternum. Therefore, when a rib is elevated, it moves the anterior thoracic wall forward relative to the fixed the posterior wall. • This results in a “pump handle” movement of the ribs and sternum that increases the anteroposterior dimensions of the thorax, i.e. when the ribs are elevated, they move the sternum upward and forward. • In addition, the middle part of each rib is lower than its two ends. So when this region of the rib is elevated, it expands the thoracic wall laterally. • Resulting in a “bucket handle” movement of the middle shaft of the ribs and increasing the lateral dimensions of the thorax • During quiet breathing, The diaphragm and the intercostal muscles to a lesser extent drive respiration • Any muscles attaching to the ribs can potentially move one rib relative to another and therefore act as accessory respiratory muscles, 40• A pneumothorax is a collec▯on of gas or air within the pleural cavity • Normally, the pleural cavity is maintained at a nega▯ve pressure (i.e. less than atmospheric pressure) by the inward elas▯c recoil of the lung and the outward pull of the chest wall. • When air enters the pleural cavity, this nega▯ve pressure is lost and the elas▯city of the lung ▯ssue causes the lung to collapse within the chest, affec▯ng the normal lung func▯on. Pneumothorax can be broadly classified as either spontaneous or acquired • Spontaneous can be further classified as primary spontaneous, or secondary spontaneous pneumothorax if there is an underlying lung disease. • Acquired pneumothorax can be because of trauma (such as blunt trauma in motor vehicle accidents or stab wounds) or iatrogenic injury (due to medical interven▯ons). 41• Most pneumothoraxes are spontaneous. • Primary, or simple pneumothorax, is most o▯en caused by rupture of subpleural apical blebs. • Smoking is the biggest risk factor (x20) • Other risk factors include family history, tall and thin body build, age <40 years, chest trauma etc. • Secondary spontaneous occurs as a complica▯on of an underlying lung disease (such as COPD, severe asthma, Tuberculosis etc). • In COPD pa▯ents, an emphysematous bullae can rupture. • Bullae is a permanent collec▯on of air (>1cm), i.e. deas ace • Bleb <1cm air pockets Trauma▯c pneumothoraxes can be closed (where air enters the pleural cavity through a hole in the lung but the thoracic wall in unaffected) or open, when air enters the pleural cavity through a hole in the chest wall (such as following penetra▯ng trauma) 42• A tension pneumothorax occurs when the air accumulates within the pleural cavity during inspira▯on, without any escape, and the posi▯ve pressure increases to such an extent that the medias▯num is “pushed” to the opposite side (a medias▯nal shi▯), compromising the other lung. • This requires urgent treatment. • The symptoms of pneumothorax are o▯en determined by the degree of air leak and the rate at which the accumula▯on of gas occurs and the ensuing lung collapses. • It can range from being asymptoma▯c to lifethreatening. • They include • Sudden, severe stabbing pain, usually on- ided and worse on inspira▯on • Dyspnoea (shortness of breath) • cardiorespiratory collapse if severe. • During a physical examina▯on, you’d find reduced expansion of the chest wall, reduced/absent breath sounds and hyper resonant percussions on the affected side. 43• The trachea might be deviated away from the affected side in severe tension pneumothoraxes 43Diagnosis is confirmed by an erect chest-Xay, but a tension pneumothorax is an emergency and requires immediate treatment. • A chest x-ray will show an area between the lung ▯ssue and the chest wall where there are no lung markings. • There will be a line demarca▯ng the edge of the lung where the lung markings ends and the pneumothorax begins. *radiolucency = transparency to -ray* 444546•Immediately decompress the pleural cavity by inser▯ng a large bore cannula into the second intercostal space in the midclavicular line. •Once the pressure is relieved with a cannula then a chest drain is required for defini▯ve management. Thoracostomy (chest) tube • Inser▯on of a chest tube is a commonly performed procedure and is indicated to relieve air or fluid trapped in the pleural cavity. • Chest drains are inserted into thet“iangle of safet”. This triangle is formed by: • The 5th intercostal space(or the inferior nipple line) • The mid axillary line(or the lateral edge of thela▯ssimus dorsi) • The anterior axillary line(or the lateral edge of thepectoris major) • Because the neurovascular bundle lies just below the rib, the tube is posi▯oned on the superior border of the rib below (i.e., at the lowest posi▯on in the intercostal space). • Anaesthe▯c should be applied to the superior border of the rib and the inferior aspect of the intercostal space, including one rib 47 and space above and one rib and space below • Connect tubing to water seal or suc▯oning. • Once the chest drain is inserted obtain a chest-xay to check the posi▯oning. 474849