Posterior Mediastinum, Trachea, Bronchi, Lungs, and Pleura PDF

GROSS ANATOMY Thorax 3 - Posterior Mediastinum, Trachea, Bronchi, Lungs, and Pleura | Lecture by Dr. Estrada COURSE OUTLINE POSTERIOR MEDIASTINUM I POSTERIOR MEDIASTINUM A. Boundaries...

GROSS ANATOMY Thorax 3 - Posterior Mediastinum, Trachea, Bronchi, Lungs, and Pleura | Lecture by Dr. Estrada COURSE OUTLINE POSTERIOR MEDIASTINUM I POSTERIOR MEDIASTINUM A. Boundaries B. Contents of the Posterior Mediastinum a. Thoracic Aorta b. Esophagus i. Blood Supply ii. Venous Drainage iii. Nerve Supply iv. Lymphatic Drainage c. Thoracic Duct d. Azygos Vein e. Hemi-Azygos Vein f. Thoracic Sympathetic Trunks II TRACHEA, BRONCHI, LUNGS, PLEURA A. Trachea a. Blood Supply b. Venous Drainage c. Nerve Supply d. Lymphatic Drainage B. Bronchi C. Lungs a. Surfaces of the Lung b. Hilum of the Lung c. Root of the Lung d. Borders of the Lung e. Right Lung f. Left Lung g. Blood Supply h. Venous Drainage i. Pulmonary Circulation Figure 1. Posterior Mediastinum j. Nerve Supply k. Lymphatic Drainage D. Pleura BOUNDARIES OF THE POSTERIOR MEDIASTINUM a. Parts / Layers of Pleura i. Parietal Pleura ii. Visceral Pleura b. Parts of the Parietal Pleura SUPERIOR Transverse thoracic plane c. Pleural Recesses passing through the sternal d. Blood Supply e. Venous Drainage angle and the junction of f. Nerve Supply T4 and T5 vertebrae g. Lymphatic Drainage E. Surface Anatomy INFERIOR Diaphragm References ANTERIOR Pericardium and Diaphragm POSTERIOR T5 - T12 Vertebrae LATERAL Mediastinal Pleurae ALCANTARA, A., ASI, BELANDRES, CLUTARIO, DIZON,IBIAS, MALABANAN, OLAN, PUNZALAN, QUINTANA, SATUR Thorax 3 - Posterior Mediastinum, Trachea, Bronchi, Lungs, and Pleura Lecture by: Dr. Estrada ESOPHAGUS Figure 2 Figure 3 CONTENTS OF THE POSTERIOR MEDIASTINUM Tubular structure about 25 cm (10 in.) long that is continuous above the laryngopharynx opposite the 6th cervical vertebrae THORACIC AORTA Passes through the diaphragm at the level of the 10th thoracic vertebra joining the stomach Inferior to the level of the root of the lungs A continuation of the arch of the aorta ○ Vagus Nerves leave the pulmonary plexus, Begins on the left side of the inferior border of the and join the sympathetic nerves to form body of the T4 vertebra and descends in the the esophageal plexus posterior mediastinum on the left sides of the Anterior to the Esophagus: Left Vagus Nerve T5-T12 vertebrae Posterior to the Esophagus: Right Vagus Nerve Terminates anterior to the inferior border of the T12 At the opening in the diaphragm, the esophagus is vertebra and enters the abdomen through the accompanied by two vagus nerves, branches, and aortic hiatus in the diaphragm tributaries of the left gastric blood vessels, and The thoracic duct and azygos vein ascend on the lymphatic vessels right side of the thoracic aorta and accompany it Fibers from the right crus of the diaphragm pass through the aortic hiatus around the esophagus in the form of a sling BRANCHES OF THE THORACIC AORTA ________________________________________________ ADDITIONAL NOTES: Esophageal Arteries Extends from the neck at the level of C6 Bronchial Arteries vertebra, as the distal continuation of the pharynx Pericardial Arteries Posterior to the trachea in the neck, and in the Mediastinal Arteries superior mediastinum Superior Phrenic Arteries Ends in the abdomen, where it joins the Stomach Posterior Intercostal Arteries at the level of T11 Vertebra Subphrenic Arteries Three segments according to the location: ○ Cervical ○ Thoracic ○ Abdominal Physiologic Constrictions of Esophagus ○ 1st Constriction: At the junction between the pharynx, and esophagus at the level of C6 vertebra Narrowest among the constrictions ○ 2nd Constriction: At the level of T4, where it is crossed by the left primary bronchus, and the arch of aorta ALCANTARA, A., ASI, BELANDRES, CLUTARIO, DIZON,IBIAS, MALABANAN, OLAN, PUNZALAN, QUINTANA, SATUR Thorax 3 - Posterior Mediastinum, Trachea, Bronchi, Lungs, and Pleura Lecture by: Dr. Estrada ○ 3rd Constriction: At the level of T10, NERVE SUPPLY OF ESOPHAGUS where it passes through the esophageal ________________________________________________ hiatus of the diaphragm The esophagus is supplied by parasympathetic and BLOOD SUPPLY OF ESOPHAGUS sympathetic efferent and afferent fibers via the ________________________________________________ vagus nerves and sympathetic trunks The upper third of the esophagus is supplied by LYMPHATIC DRAINAGE OF ESOPHAGUS the inferior thyroid artery ________________________________________________ The middle third by branches from the descending thoracic aorta Lymph vessels from the upper third of the The lower third by branches from the left gastric esophagus drain into the deep cervical nodes, from artery the middle third into the superior and posterior mediastinal nodes, and from the lower third into nodes along the left gastric blood vessels and the celiac nodes Figure 4. Blood Supply of Esophagus VENOUS DRAINAGE OF ESOPHAGUS Figure 6. Lymphatic Drainage of Esophagus ________________________________________________ The veins from the upper third of the esophagus drain into the inferior thyroid veins, from the middle third into the azygos vein, and from the lower third into the left gastric vein, a tributary of the portal vein Figure 5. Venous Drainage of Esophagus Figure 7 ALCANTARA, A., ASI, BELANDRES, CLUTARIO, DIZON,IBIAS, MALABANAN, OLAN, PUNZALAN, QUINTANA, SATUR Thorax 3 - Posterior Mediastinum, Trachea, Bronchi, Lungs, and Pleura Lecture by: Dr. Estrada THORACIC DUCT AZYGOS VEIN Begins in the abdomen as a dilated sac, the Arises from the posterior aspect of the inferior vena cisterna chyli cava at the level of the renal veins and enters the It ascends through the aortic opening in the posterior mediastinum through the aortic hiatus of diaphragm, on the right side of the descending the diaphragm aorta Forms a collateral pathway between the superior The thoracic duct then runs upward along the left vena cava and inferior vena cava and drains blood edge of the esophagus to enter the root of the neck from the posterior walls of the thorax and abdomen It turns downward in front of the left phrenic nerve Ascends in the posterior mediastinum, passing and crosses the subclavian artery to enter the close to the right sides of the bodies of the inferior 8 junction of the left internal jugular vein and left thoracic vertebrae subclavian vein It arches over the superior aspect of the root of the The thoracic duct conveys to the blood all lymph right lung to join the superior vena cava from the lower limbs, pelvis, abdomen except the Main Tributary: Hemiazygos Vein convex surface of the liver, left side of the thorax The azygos vein also receives the accessory including the trachea and esophagus, left side of hemi-azygos vein, the posterior intercostal veins, the head and neck, and left upper limb the vertebral venous plexuses that drain the back, vertebrae, and structures in the vertebral canal, the mediastinal veins, the esophageal veins, and the bronchial veins. Figure 8 Figure 10 HEMI-AZYGOS VEIN The hemi-azygos vein arises on the left side by the junction of the left subcostal and ascending lumbar veins It ascends on the left side of the vertebral column, posterior to the thoracic aorta as far as the T9 vertebra; here it crosses to the right and joins the azygos vein Figure 9 ALCANTARA, A., ASI, BELANDRES, CLUTARIO, DIZON,IBIAS, MALABANAN, OLAN, PUNZALAN, QUINTANA, SATUR Thorax 3 - Posterior Mediastinum, Trachea, Bronchi, Lungs, and Pleura Lecture by: Dr. Estrada TRACHEA The trachea is a mobile cartilaginous and membranous tube It begins in the neck as a continuation of the larynx at the lower border of the cricoid cartilage at the level of the 6th cervical vertebra It descends in the midline of the neck In the thorax, the trachea ends below at the carina by dividing into right and left principal (main) bronchi at the level of the sternal angle (opposite the IV disc between the 4th and 5th thoracic vertebrae) In adults, the trachea is about 11.25 cm (4.5 in.) long and 2.5 cm (1 in.) in diameter Figure 11. Azygos and Hemiazygos Veins The fibroelastic tube is kept patent by the presence of U-shaped rings of hyaline cartilage embedded in its wall THORACIC SYMPATHETIC TRUNKS The posterior free ends of the cartilage are connected by smooth muscle, the trachealis muscle The thoracic sympathetic trunks are in continuity with the cervical and lumbar sympathetic trunks The lower thoracic splanchnic nerves – also known as greater, lesser, and least splanchnic nerves – are part of the abdominopelvic splanchnic nerves because they supply viscera inferior to the diaphragm They consist of mainly presynaptic fibers from the 5th through the 12th sympathetic ganglia, which pass through the diaphragm and synapse in prevertebral ganglia in the abdomen They supply sympathetic innervation for most of the abdominal viscera Figure 13 Figure 12 Figure 14 ALCANTARA, A., ASI, BELANDRES, CLUTARIO, DIZON,IBIAS, MALABANAN, OLAN, PUNZALAN, QUINTANA, SATUR Thorax 3 - Posterior Mediastinum, Trachea, Bronchi, Lungs, and Pleura Lecture by: Dr. Estrada BLOOD SUPPLY OF THE TRACHEA ________________________________________________ The upper two thirds of the trachea are supplied by the inferior thyroid arteries The lower third is supplied by the bronchial arteries VENOUS DRAINAGE OF THE TRACHEA ________________________________________________ The inferior thyroid vein, tributary of the brachiocephalic vein, drains the trachea NERVE SUPPLY OF THE TRACHEA ________________________________________________ The sensory nerve supply is from the vagus nerves and the recurrent laryngeal nerves Sympathetic nerves supply the trachealis muscle Figure 16 LYMPHATIC DRAINAGE OF THE TRACHEA ________________________________________________ RIGHT PRINCIPAL BRONCHUS The lymph drains into the pretracheal and paratracheal lymph nodes and the deep cervical The right principal bronchus is wider, shorter, and lymph nodes. more vertical than the left and is about 2.5 cm (1 in.) long Before entering the hilum of the right lung, the principal bronchus gives off the superior lobar bronchus On entering the hilum, it divides into a middle lobar bronchus and an inferior lobar bronchus LEFT PRINCIPAL BRONCHUS The left principal bronchus is narrower, longer, and more horizontal than the right and is about 5 cm (2 in.) long. On entering the hilum of the left lung, the principal bronchus divides into a superior lobar bronchus and an inferior lobar bronchus. Sympathetic stimulation of the bronchial tree causes bronchodilation Parasympathetic stimulation of the bronchial tree causes bronchoconstriction Figure 15 BRONCHI BRONCHI The trachea bifurcates behind the arch of the aorta into the right and left principal (primary or main) bronchi The bronchi divide dichotomously, giving rise to several million terminal bronchioles that terminate in one or more respiratory bronchioles Each respiratory bronchiole divides into 2 to 11 alveolar ducts that enter the alveolar sacs The alveoli arise from the walls of the sacs as diverticula ALCANTARA, A., ASI, BELANDRES, CLUTARIO, DIZON,IBIAS, MALABANAN, OLAN, PUNZALAN, QUINTANA, SATUR Thorax 3 - Posterior Mediastinum, Trachea, Bronchi, Lungs, and Pleura Lecture by: Dr. Estrada At about the middle of the mediastinal surface is the hilum, a depression in which the bronchi, blood vessels, and nerves that form the root enter and leave the lung HILUM OF LUNG A wedge-shaped area on the mediastinal surface of each lung through which the structures forming the root of the lung pass to enter or exit the lun Inferior to the root of the lung, the continuity between parietal and visceral pleura forms the pulmonary ligament, extending between the lung and the mediastinum, immediately anterior to the esophagus Figure 17 LUNGS During life, the right and left lungs are soft and spongy and very elastic Figure 18. Surfaces of the Lung If the thoracic cavity were opened, the lungs would immediately shrink to one third or less in volume In the child, the lungs are pink, but with age, they become dark and mottled because of the inhalation of dust particles that become trapped in the phagocytes of the lungs ○ This is especially well seen in city dwellers and coal miners ROOT OF LUNG The lungs are situated so that one lies on each side of the mediastinum The root of the lung is formed of structures that ○ They are therefore separated from each are entering or leaving the lung other by the heart and great vessels and It is made up of the bronchi, bronchial vessels, other structures in the mediastinum pulmonary arteries, superior and inferior pulmonary Each lung is conical, covered with visceral pleura, veins, the pulmonary plexus of nerves (sympathetic, and suspended free in its own pleural cavity, being parasympathetic, and visceral afferent fibers), and attached to the mediastinum only by its root lymphatic vessels The root of the lung attaches the lung to the SURFACES OF THE LUNG mediastinal pleura The root of the lung is surrounded by a tubular sheath of pleura, which joins the parietal Each lung has a blunt apex, which projects mediastinal pleura to the visceral pleura covering upward into the neck for about 2.5 cm (1 in.) above the lungs the clavicle; a concave diaphragmatic surface that forms the base that sits on the diaphragm; a ★ Root of the lung is the collective term for the convex costal surface, which corresponds to the structures found within the hilum. concave chest wall; and a concave mediastinal surface, which is molded to the pericardium and other mediastinal structures ALCANTARA, A., ASI, BELANDRES, CLUTARIO, DIZON,IBIAS, MALABANAN, OLAN, PUNZALAN, QUINTANA, SATUR Thorax 3 - Posterior Mediastinum, Trachea, Bronchi, Lungs, and Pleura Lecture by: Dr. Estrada Figure 19. Medial view of the Right lung Figure 21. Right Lung BORDERS OF LUNG LEFT LUNG ANTERIOR BORDER: Where the costal and The left lung is divided by a similar oblique fissure mediastinal surfaces meet anteriorly and overlap into two lobes: the superior (upper) lobe and the heart; the cardiac notch indents this border of inferior (lower) lobe the left lung There is no horizontal fissure in the left lung INFERIOR BORDER: Circumscribes the diaphragmatic surface of the lung and separates this surface from the costal and mediastinal surfaces POSTERIOR BORDER: Where the costal and mediastinal surfaces meet posteriorly Figure 22. Left Lung BLOOD SUPPLY OF THE LUNGS ________________________________________________ Figure 20. Borders of the Lungs The bronchi, the connective tissue of the lung, and the visceral pleura receive their blood supply from RIGHT LUNG the bronchial arteries, which are branches of the descending thoracic aorta The right lung is slightly larger than the left and is divided by the oblique fissure and horizontal fissure into three lobes: the superior (upper) lobe, middle lobe, and inferior (lower) lobe ALCANTARA, A., ASI, BELANDRES, CLUTARIO, DIZON,IBIAS, MALABANAN, OLAN, PUNZALAN, QUINTANA, SATUR Thorax 3 - Posterior Mediastinum, Trachea, Bronchi, Lungs, and Pleura Lecture by: Dr. Estrada Figure 25. Azygos and Hemiazygos Veins Figure 23. Bronchial Arteries PULMONARY CIRCULATION (Highlighted in Yellow) ________________________________________________ VENOUS DRAINAGE OF THE LUNGS The alveoli receive deoxygenated blood from the ________________________________________________ terminal branches of the pulmonary arteries The oxygenated blood leaving the alveolar The bronchial veins (which communicate with the capillaries drains into the tributaries of the pulmonary veins) drain into the azygos and pulmonary veins, which follow the intersegmental hemiazygos veins connective tissue septa to the lung root Two pulmonary veins leave each lung root to empty into the left atrium of the heart Figure 24. Venous drainage of lungs from left and right bronchial veins and into the azygos vein Figure 26. Diagram of the Pulmonary Circulation ALCANTARA, A., ASI, BELANDRES, CLUTARIO, DIZON,IBIAS, MALABANAN, OLAN, PUNZALAN, QUINTANA, SATUR Thorax 3 - Posterior Mediastinum, Trachea, Bronchi, Lungs, and Pleura Lecture by: Dr. Estrada NERVE SUPPLY OF LUNGS ________________________________________________ At the root of each lung is a pulmonary plexus composed of efferent and afferent autonomic nerve fibers The plexus is formed from branches of the sympathetic trunk and receives parasympathetic fibers from the vagus nerve The sympathetic efferent fibers produce bronchodilation and vasoconstriction The parasympathetic efferent fibers produce bronchoconstriction, vasodilatation, and increased glandular secretion Figure 29. Lymphatic Drainage of Lungs PLEURA A serous membrane that folds back on itself to form a two-layered membranous pleural cavity PARTS / LAYERS OF PLEURA Lines the thoracic wall, covers the thoracic surface of the diaphragm and the PARIETAL PLEURA lateral aspect of the mediastinum and extends into the root of the neck to line the undersurface of the suprapleural membrane (Sibson’s fascia) that closes the thoracic inlet Figure 27. Nerve Supply of the Lungs Completely covers the outer surfaces of the lungs VISCERAL PLEURA and extends into the depths LYMPHATIC DRAINAGE OF LUNGS of the interlobar fissures ________________________________________________ The lymph vessels originate in superficial and deep plexuses; they are not present in the alveolar walls The two layers of pleura become continuous with The superficial (subpleural) plexus lies beneath one another by means of a cuff of pleura that the visceral pleura and drains over the surface of surrounds the structures entering and leaving the the lung toward the hilum, where the lymph vessels lung at the hilum of each lung enter the bronchopulmonary nodes To allow for movement of the pulmonary vessels The deep plexus travels along the bronchi and and large bronchi during respiration, the pleural cuff pulmonary vessels toward the hilum of the lung, hangs down as a loose fold called the pulmonary passing through pulmonary nodes located within ligament the lung substance; the lymph then enters the The parietal and visceral layers of pleura are bronchopulmonary nodes in the hilum of the lung separated from one another by a slit-like space All the lymph from the lung leaves the hilum and called the pleural cavity (pleural space) drains into the tracheobronchial nodes and then The pleural cavity normally contains a small amount into the bronchomediastinal lymph trunks of tissue fluid, the pleural fluid, which covers the surfaces of the pleura as a thin film and permits the two layers to move on each other with the minimum of friction. ALCANTARA, A., ASI, BELANDRES, CLUTARIO, DIZON,IBIAS, MALABANAN, OLAN, PUNZALAN, QUINTANA, SATUR Thorax 3 - Posterior Mediastinum, Trachea, Bronchi, Lungs, and Pleura Lecture by: Dr. Estrada MEDIASTINAL PLEURA ________________________________________________ The mediastinal pleura covers and forms the lateral boundary of the mediastinum During full inspiration, the lungs expand and fill the pleural cavities However, during quiet inspiration, the lungs do not fully occupy the pleural cavities at four sites FOUR SITES ★ Right costodiaphragmatic recesses ★ Left costodiaphragmatic recesses ★ Right costomediastinal recesses ★ Left costomediastinal recesses DIAPHRAGMATIC PLEURA ________________________________________________ The diaphragmatic pleura covers the thoracic surface of the diaphragm CERVICAL PLEURA Figure 30 ________________________________________________ The cervical pleura extends up into the neck, lining the undersurface of the suprapleural membrane. It reaches a level 2.5 to 4 cm (1 to 1.5 in.) above the medial third of the clavicle. The cervical pleura forms a cup-like dome (pleural cupula) over the apex of the lung The cervical pleura is a superior continuation of the costal and mediastinal pleurae. Figure 31. Suprapleural Membrane Figure 32. Parts of Parietal Pleura PARTS OF THE PARIETAL PLEURA PLEURAL RECESSES COSTAL PLEURA ________________________________________________ COSTODIAPHRAGMATIC RECESSES The costal pleura lines the inner surfaces of the ribs, the costal cartilages, the intercostal spaces, The costodiaphragmatic recesses are slit-like the sides of the vertebral bodies, and the back of spaces between the costal and diaphragmatic the sternum parietal pleurae that are separated only by a capillary layer of pleural fluid During inspiration, the lower margins of the lungs descend into the recesses ALCANTARA, A., ASI, BELANDRES, CLUTARIO, DIZON,IBIAS, MALABANAN, OLAN, PUNZALAN, QUINTANA, SATUR Thorax 3 - Posterior Mediastinum, Trachea, Bronchi, Lungs, and Pleura Lecture by: Dr. Estrada During expiration, the lower margins of the lungs ascend so that the costal and diaphragmatic pleurae come together again COSTOMEDIASTINAL RECESSES The costomediastinal recesses are situated along the anterior margins of the pleura They are slit-like spaces between the costal and mediastinal parietal pleurae, which are separated by a capillary layer of pleural fluid During inspiration and expiration, the anterior borders of the lungs slide in and out of the recess Figure 35. Venous Drainage of Pleura NERVE SUPPLY OF PLEURA ________________________________________________ The visceral pleura is sensitive to stretch but is insensitive to common sensations such as pain and touch It receives autonomic nerve supply from the Figure 33. Pleural Recesses pulmonary plexus The parietal pleura is sensitive to pain, temperature, touch, and pressure and is supplied as follows: BLOOD SUPPLY OF PLEURA ○ The costal pleura is segmentally supplied ________________________________________________ by the intercostal nerves ○ The mediastinal pleura is supplied by the The bronchial arteries, which are branches of the phrenic nerve descending thoracic aorta, supply the visceral ○ The diaphragmatic pleura is supplied over pleura the domes by the phrenic nerve and The intercostal and pericardial arteries supply around the periphery by the lower six the parietal pleura intercostal nerves Figure 34. Blood Supply of Pleura VENOUS DRAINAGE OF PLEURA ________________________________________________ Figure 36. Nerve Supply of Pleura The bronchial veins drain the visceral pleura LYMPHATIC DRAINAGE OF PLEURA The right bronchial vein drains into the azygos ________________________________________________ vein, and the left bronchial vein drains into the accessory hemi-azygos vein or the left superior The lymph drainage of the visceral pleura follows intercostal vein the lymph drainage of the lungs The intercostal veins drain the parietal pleura Lymphatic vessels are located in the submesothelial The intercostal veins drain into the azygos vein layer of the parietal pleura (for the right-sided pleura) and into the hemiazygos Lymphatic vessels in the anterior parietal pleura veins (for the left-sided pleura) drain to the intercostal lymph nodes and lymphatic vessels in the posterior parietal pleura drain to the ALCANTARA, A., ASI, BELANDRES, CLUTARIO, DIZON,IBIAS, MALABANAN, OLAN, PUNZALAN, QUINTANA, SATUR Thorax 3 - Posterior Mediastinum, Trachea, Bronchi, Lungs, and Pleura Lecture by: Dr. Estrada lymph nodes located along the internal thoracic artery SURFACE ANATOMY The lower border of the lung in mid-inspiration follows a curving line, which crosses the 6th rib in the midclavicular line and the 8th rib in the midaxillary line, and reaches the 10th rib adjacent to the vertebral column posteriorly Figure 39 The lower margins of the lungs cross the 6th, 8th, and 10th ribs at the midclavicular lines, the midaxillary lines, and the sides of the vertebral column, respectively; the lower margins of the pleura cross, at the same points, the 8th, 10th, and 12th ribs, respectively ★ The distance between the two borders corresponds to the costodiaphragmatic recess Figure 37 The lower border of the pleura on both sides follows a curved line, which crosses the 8th rib in the midclavicular line and the 10th rib in the midaxillary line, and reaches the 12th rib adjacent to the vertebral column – that is, at the lateral border of the erector spinae muscle Figure 40 REFERENCES Dr. Estrada’s Lecture (2024) Snell’s Clinical Anatomy by Systems (10th ed.) Figure 38 ALCANTARA, A., ASI, BELANDRES, CLUTARIO, DIZON,IBIAS, MALABANAN, OLAN, PUNZALAN, QUINTANA, SATUR