Thoracic cavity.pdf

Thoracic Cavity 1 & 2 Mr Fraser Chisholm [email protected] Where this fits: Anatomy Lectures Dissection Guided studies Thoracic Wall 1&2 Osteology of the thoracic cage Overview of the thoracic cage Thoracic cavity 1&2 Removal of the anterior thoracic wall Changes to circulation at birth Heart and pericardium Cross-sectional anatomy of the thorax Heart: internal structure and surface anatomy Surface anatomy of the neck Superior Mediastinum Coronary circulation and conduction Posterior mediastinum Foetal circulation Development of heart and great arteries Nerves of the thorax 2 Learning Outcomes: After this lecture, time spent in the dissecting room, and further private study you should be able to: 1. Describe the general arrangement of the pleura and pericardium 2. Define the term mediastinum and describe the boundaries of its subdivisions 3. List the contents of the anterior, middle, superior and posterior mediastina 4. Describe the fibrous and serous pericardium, and pericardial cavity 5. Describe the position and relations of the transverse and oblique sinuses of the serous pericardium 6. Describe the course and distribution of the right and left phrenic nerves 7. Describe why irritation of the phrenic nerve will result in referred pain to the shoulder 8. Discuss the clinical conditions that affect the pericardium 9. Describe the position of the thymus 10. Describe the posterior relations of the manubrium 11. Describe the relationships of the structures within the mediastina 12. Describe the clinical anatomy of the thoracic aorta 13. Describe the functional anatomy of the trachea 14. Describe the clinical anatomy of the oesophagus 15. Describe the lymph drainage of the mediastinal nodes 16. Describe the clinical anatomy of the thoracic duct 17. Discuss the clinical relevance of the structures within the mediastina 18. Identify anatomical structures on medical images through the thorax 3 Recommended Reading, Related elements • MD3001 Practical notes “The heart and pericardium” in week 3 • MD3001 Practical notes “Superior mediastinum” in week 4 • MD3001 Practical notes “Posterior mediastinum” in week 5 • Moore et al. Clinically Oriented Anatomy 8th Ed, 2018 © Wolters Kluver. • Thorax chapter: Viscera of the Thorax – skip sections on Lungs and Heart- more on those later 4 Body Cavities • Confine organs and systems that have related functions • Lined by serous membranes • Allows movement, expansion, contraction of organs • Compartmentalize • With miniscule layer of fluid;lubricated potential space; friction free • Thoracic cavity: Lungs and chest wall, lined by pleura; Heart covered by pericardium • Abdominal and Pelvic cavities lined by the peritoneum 5 Invagination Visceral – Visceral layer Pleural Cavity Paries – Parietal layer 6 Pleura and Pleural Cavity • The thoracic cavity is divided into three compartments • The left and right pleural cavities are independent, with the mediastinum between them • Pleura covers the lungs, reflects onto itself around the root of the lung and cover the diaphragm and the thoracic wall Figure from, Core Anatomy Illustrated, Parkin et al, Hodder Arnold, 1st Ed 2007 7 Parietal Pleura Parietal pleura is attached firmly to: • Thorax wall (costal pleura) • The fascia at the thoracic inlet, at 1st rib and T1 • Fibrous pericardium and other mediastinal structures (mediastinal pleura) • Diaphragm (diaphragmatic pleura) 8 Parietal Pleura - Parts 9 Mediastinum • Space between the two pleural sacs, the sternum and costal cartilages, thoracic vertebrae, diaphragm • Highly mobile region allowing volume and pressure changes Drake Fig. 3.5 Drake Fig. 3.50 10 Mediastinum • Superior Mediastinum • behind manubrium, between the inlet and the plane through the sternal angle (and T4/5 disc) • Inferior Mediastinum • inferior to the transverse plane through the sternal angle and the diaphragm Anterior Middle • Inferior mediastinum is further subdivided into: • Anterior mediastinum • Middle mediastinum • Posterior mediastinum Posterior Drake Fig. 3.5 11 Mediastinum Structures on the right of the mediastinum are related to the right atrium and veins - Superior Vena Cava - Arch of the azygos - Inferior Vena Cava 12 Mediastinum Structures on the left of the mediastinum are related to Left ventricle and arteries - Left common carotid artery - Left subclavian artery - Arch of aorta - Thoracic aorta 13 Middle mediastinum • Centrally located Aorta • Contains • Heart • Pericardium • Origins of great vessels (aorta, pulmonary trunk), terminal parts of SVC and IVC • Smaller vessels (pulmonary veins) • Phrenic nerves • Branches of Vagus Pulmonary Trunk Opened pericardial sac Thiel Fig. 114 14 Pericardium • Fibro-serous sac that encloses the heart and the roots of the great vessels • Functions: • Anchoring the heart to surrounding tissues without compromising cardiac movement • Preventing overfilling (overexpansion) of the heart Thiel Fig. 111 • Comprises two layers: • Fibrous pericardium (externally) • Serous pericardium (internally) 15 Fibrous Pericardium • The apex is fused with the adventitia of the great vessels • Anteriorly, related and attached by the sterno-pericardial ligament to the body of the sternum, and 3rd- 6th costal cartilages • Posteriorly, related and attached by the pericardiovertebral ligaments to 5th - 8th thoracic vertebrae From, http://www.oddee.com/item_96547.aspx 16 Fibrous Pericardium • Inferiorly it blends with the central tendon of the Diaphragm (Pericardiophrenic ligament) • Attachment of fibrous pericardium to diaphragm halts descent of the diaphragm during inspiration. WHY? 17 Serous Pericardium • Has two layers: Parietal and visceral • Parietal layer: • Lines the inner aspect of the fibrous pericardium • Reflects onto itself around the roots of the great vessels and continues as the visceral layer • Visceral layer = epicardium 18 Pericardial Cavity & Fluid • Pericardial cavity: • Between parietal and visceral layers of serous pericardium • Pericardial fluid: • 10-15 mL • Produced by serous pericardium • Reduce friction during contraction of the heart 19 Pericardial Sinuses • During embryological development, the heart tube folds and invaginates into the serous pericardium (within the fibrous sac) • 2 sinuses are formed within the serous pericardium 20 Transverse Pericardial Sinus • Separates the arterial and venous ends of the heart tube • Posterior to the ascending aorta and pulmonary trunk, anterior to the superior vena cava. • Superior to the left atrium and the pulmonary veins 21 Oblique pericardial sinus • Haller's cul-de-sac • Surrounded by the reflection of the serous pericardium around the right and left pulmonary veins and the inferior vena cava 22 Pericardium – Nerve Supply Phrenic N. • Sensory fibres Phrenic N. • Vasomotor Splanchnic nerves Vagus N. Vagus N. 23 Phrenic Nerve • A branch of the cervical plexus • Arises from ventral rami of C3,4,5 • On scalenus anterior muscle • Enters the mediastinum between the venous and the arterial planes (subclavian a. and subclavian v.) 24 Phrenic Nerve Figures from, Human Sectional Anatomy: Pocket Atlas of Body Sections, CT and MRI images, Ellis et al, 4th Edition, 2015 © CRC Press • Passes anterior to the root of lung • Lies between fibrous pericardium and parietal pleura • Right phrenic nerve passes through the Caval hiatus 25 Phrenic Nerve • Right: Adjacent to superior vena cava, then inferior vena cava • Passes through the Caval hiatus • Left: Crosses the aortic arch • Follows left ventricle 26 Phrenic Supply • Sole motor supply to the diaphragm • Also supplies sensory fibres to • the mediastinal parietal pleura • peritoneum and pleura related to the central tendon of the diaphragm • parietal pericardium Netter Fig. 190B 27 Referred Pain • Supraclavicular Nerves: C3-4 • Lateral supraclavicular nerve supplies skin over shoulder, which is the C4 dermatome • Therefore, structures with a sensory supply via the phrenic may refer pain to the back of neck, the supraclavicular region, shoulder tip 28 Phrenic Nerve Injury • Division of the phrenic nerve in the neck? • Radial incisions in the diaphragm from the costal margin to the oesophageal hiatus • Cardiac surgery: instillation of saline slush for myocardial preservation • Thoracic surgery • Lung tumours • Mediastinal tumours • Polio • Iatrogenic 29 Anterior Medistinum • Prevascular compartment • Boundaries: • Sternal body and xiphisternum • pericardium • lungs with pleura Contents: • Thymus (±) • Internal thoracic vessels • Lymph nodes • Connective tissue • Fat tissue • Lower pole of Thyroid • Ectopic parathyroid 30 Thymus Gland • Bi-lobed organ of lymphoid tissue • Between the manubrium, sternum and pericardium • Related to Pericardium; Superior vena cava and aorta; Left and Right brachiocephalic veins; Pleura; Phrenic nerves; Trachea • Extends from lower neck (jugular notch) to 4th costal cartilage (sometimes below aortic arch) • Active in childhood until puberty • Increasing fibro-fatty infiltration with age To review its function, refer to MD2002 lecture in week 6 “B and T Cells and MHC” 31 Superior Mediastinum • Structures in the superior mediastinum are “arranged” in 3 planes • The Vagus and phrenic nerves lie between 2 of these planes Venous plane Arterial plane Visceral plane 32 Venous Plane • The brachiocephalic veins (BCV) are formed by the Internal jugular (IJV) and subclavian (ScV) veins • Left BCV passes anterior to the arch of the aorta; posterior to the manubrium • Superior vena cava (SVC) is formed by right and left BCVs • The arch of the azygos vein joins SVC • SVC enters the right atrium 33 Arterial Plane • Ascending aorta with its branches (coronary arteries) are in the middle mediastinum • Ascending aorta continues as the Aortic arch above the sternal angle - T4/5 plane • Aortic arch curves up, backwards and slightly left behind the lower half of the manubrium • Continues as the Thoracic (descending) aorta in the posterior mediastinum 34 Aortic Arch • Aortic arch has 3 branches: 1. Brachiocephalic trunk • Divides into right subclavian and right common carotid arteries 2. Left common carotid artery 3. Left subclavian artery • Posterior and to the left of the trachea 35 Pulmonary arteries • The pulmonary trunk lies within the pericardium to the left of the ascending aorta • At the level of T4/5 disc, inferior to the Aortic arch, it divides into: • Right pulmonary artery -Posterior to the ascending aorta and Superior vena cava • Left pulmonary artery – Inferior to the arch of the aorta and anterior to the thoracic aorta 36 Trachea • Air-transport tube in midline of neck • Starts at the level of C6 vertebra, ends at tracheal bifurcation (carina) • May rise and descend to the level of T4 and T6 with deep inspiration and expiration Spratt p119 Fig. 7.15 37 Trachea Wicke Fig. 71 Wicke Fig. 72 38 Superior Mediastinum 39 Superior Mediastinum 40 41 Landmarks in the Superior Mediastinum 1. 1. Posterior to the sternoclavicular joint: Formation of the brachiocephalic veins (BCV) by the Internal jugular (IJV) and subclavian (ScV) veins; division of Brachiocephalic trunk to its branches on the right side 2. Posterior to 1st right CC: Formation of superior vena cava (SVC) by right and left BCVs 2. 3. 4. 3. Posterior to 2nd right CC: Arch of the azygos vein joins SVC 4. Posterior to 3rd right CC: SVC enters the right atrium 42 Posterior Mediastinum • Vertebral bodies • Proximal (posterior) costal segments • Proximal segments of posterior intercostal vessels • Proximal segments of intercostal nerves • Sympathetic chain with its ganglia • Trachea? 43 Thoracic Aorta • Distal continuation of the aortic arch • Between the level of sternal angle and aortic hiatus (T12) • Lies on the left of the thoracic vertebral bodies, but moves to midline in lower thorax 44 Thoracic Aorta Visceral branches • Oesophageal arteries • Bronchial arteries • Usually, 2 on the left + 1 on the right • Pericardial branches • Mediastinal branches • Superior phrenic artery Bronchial Arteries Oesophageal Arteries Parietal branches • Posterior intercostal arteries • Superior phrenic artery Posterior intercostal arteries 45 Oesophagus • Transport of food and fluid to stomach • Starts in the midline as the continuation of the pharynx at C6, inferior border of cricoid cartilage • It descends between the trachea and the vertebral column • Enters the thorax behind trachea, with the arch of the aorta to its left in the superior mediastinum 46 Oesophagus • Upper 1/3: striated muscle as swallowing is voluntary and rapid • Middle 1/3: mixed striated + smooth • Lower 1/3: smooth muscle • Stratified squamous epithelium 47 Netter Fig. 233A Oesophagus • In the lower posterior mediastinum, it swings forwards and to the left • Pierces the diaphragm at the level of T10 Wicke Fig. 76 Coronal 48 Daffner Fig. 8.17 Lateral Oesophagus Oesophagus has 4 constrictions − Upper oesophageal sphincter − Arch of aorta − Left main bronchus − Diaphragm 49 Oesophagus Barium swallow, oblique view of oesophagus Arch of Aorta Left main bronchus Left Atrium Constrictions ... • are more likely to cause blockage • hinder passage of instruments • slow down the passage of caustic substances more damage Image on right taken from, https://openi.nlm.nih.gov/detailedresult.php?img=PMC2922872_ipej100339-08&req=4 50 Oesophagus – Venous Drainage • Veins of upper and middle thirds drain to azygos, hemiazygos, accessory hemiazygos (systemic) • lower third to the left gastric vein (portal system) • There are anastomoses between the veins of middle and lower thirds. • Porto-systemic or portocaval anastomosis Cirrhotic liver disease → portal hypertension → oesophageal varices 51 Oesophagus – Nerve Supply Thoracic part • Left vagus → Anterior vagal trunk • Right vagus → Posterior vagal trunk Sympathetic Ganglion and postganglionic nerves. Right Vagus N. Left Vagus N. • Fibres from the anterior and posterior vagal trunks, together with sympathetic fibres form the oesophageal plexus around the oesophagus Post. Vagal Trunk Ant. Vagal Trunk 52 Mediastinal Lymphatics • Superior and inferior tracheobronchial nodes Superior • Clustered around the trachea and oesophagus • Receives the lymph from the lung important in spread of lung tumour Inferior 53 Mediastinal Lymphatics The posterior mediastinal nodes behind the heart and adjacent to the oesophagus The anterior mediastinal nodes are around the brachiocephalic veins 54 Lymph drainage Pulmonary Bronchopulmonary (around main bronchi) Inf. And Sup. Tracheobronchial Parasternal (Internal Thoracic) Anterior Mediastinal Paratracheal Pos. mediastinal Bronchomediastinal Lymph Trunks 55 Lymph drainage Left Jugular Lymph Trunk (Left side head and neck) Left Subclavian Lymph Trunk (Left Upper limb) Left Bronchiomediastinal Trunk (Left Thorax) The Thoracic Duct Left Brachiocephalic Vein 56 Lymph drainage Right Jugular Lymph Trunk (Right side head and neck) Right Subclavian Lymph Trunk (Right Upper limb) Right Bronchiomediastinal Trunk (Right Thorax) Right Lymphatic Duct Right Brachiocephalic Vein 57 Thoracic Duct • Carries the lymph from most of the body • Except Upper right thorax, • Right upper limb, • Right head and neck • It starts at the cisterna chyli • Lies between the aorta and azygos vein in the posterior mediastinum • Pulsation of the Aorta promotes lymph flow • At T4/5 crosses behind the oesophagus to ascend on its left side • Chylothorax cisterna chyli 58 Drake Atlas Fig. 3.94 Thoracic duct • Arches over the apex of the left lung and pleura • Opens into the left brachiocephalic vein at the junction of the left internal jugular and the left subclavian vein (Pirogoff’s angle) 59 Thoracic Duct 60 61 Sources of figures and Images • DAFFNER: Daffner & Hartman. Clinical Radiology. The Essentials ,4th Ed, 2014 © Lippincott Williams & Wilkins. • DRAKE: Drake et al. Gray’s Atlas of Anatomy 2nd Ed, 2018 © Elsevier. • KELLEY: Kelly&Petersen. Sectional Anatomy for Imaging Professionals, 3rd Edition, 2013 © Mosby, Elsevier Inc • MOORE: Moore et al. Clinically Oriented Anatomy 8th Ed, 2018 © Wolters Kluver. • SNELL: Snell R. Clinical anatomy by Regions, 9th Ed, 2011 © Lippincott Williams & Wilkins • SOBOTTA: Putz&Pabst. Sobotta Atlas of Human Anatomy, 14th Edition, 2006 © Urban and Fischer Verlag, Elsevier Inc • SPRATT: Spratt et al. Weir and Abraham’s Imaging Atlas of Human Anatomy, 5th Edition, 2017 © • Elsevier Inc. 62

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