Mediastinum & Lung Student PDF

Posterior Mediastinum, Pleural Cavity & Lungs C H R I S T I W I L L I A M S , P T, D P T, O C S , C E R T. M D T Mediastinum & Pulmonary Cavities Superior thoracic aperture Pulmonary cavities: Bilate...

Posterior Mediastinum, Pleural Cavity & Lungs C H R I S T I W I L L I A M S , P T, D P T, O C S , C E R T. M D T Mediastinum & Pulmonary Cavities Superior thoracic aperture Pulmonary cavities: Bilateral compartments that contain the lungs & pleurae The central mediastinum completely separates the 2 pulmonary cavities “standing in the middle” Contains all the structures of the thoracic cavity except the lungs Diaphragm Grant’s Atlas: Fig 1.24C Mediastinum  Mediastinum Superior thoracic aperture Superior to Inferior From superior Superior thoracic aperture to Thoracic diaphragm T4 Sternum - Separated by Vertebrae sternal angle (T4) Posterior Middle Anterior to Posterior Inferior Anterior From thoracic vertebrae to Middle sternum Posterior Diaphragm Superior Mediastinum Superior Mediastinum Superior Thymus Mediastinum Veins Great vessels Trachea Esophagus Vagus & Phrenic nerves Thoracic duct / Right lymphatic duct  Superior Mediastinum #1 Thymus gland Primary lymphoid organ Produce lymphocytes Prominent in infants Begins to diminish at puberty By adulthood, composed primarily of fat Clemente, 4th ed, Fig 227 Grant’s Atlas, Figure 1.62  Superior Mediastinum #2 Veins #3 Arteries What might these be? Clemente, 4th ed, Fig 227  #7 #6 #5 #5 #4 #4 #3 Review #1 #2 Aorta SVC  Superior Mediastinum #2 Veins - Brachiocephalic Veins & SVC Venous Angles: union of internal jugular & subclavian veins (behind SC joints) Thoracic duct and Right Lymphatic duct are located at right & left venous angles Both brachiocephalic veins meet to become the SVC Subclavian Subclavian vein vein Clemente, 4th ed, Fig 227 Superior Inferior Vena Cava Mediastinum Grant’s Atlas, Figure 1.21  Superior Mediastinum #3 #2 #4 #3 Arteries - Great Vessels Ascending Aorta / arch of aorta Right brachiocephalic trunk Common carotid arteries Subclavian arteries #1 Aorta Review  Arch of the Aorta Arches to the left Anterior to right pulmonary artery Posterior to left pulmonary artery Descends on left side of vertebral bodies Grant’s atlas, Fig 1.62B  Ligamentum Arteriosum Opening or communication between the pulmonary trunk (artery) and the aorta Before birth- do not need to send blood to lungs for oxygen Becomes ligamentum arteriosum If the opening is small there may be few symptoms If opening is large – it can cause too much blood flow into the lungs- can damage the heart and lungs  Superior Mediastinum #4 Airway (Trachea) #5 Food Passage (Esophagus) Clemente, 4th ed, Fig 227 Superior Mediastinum Esophagus Trachea #4 Trachea Anterior to esophagus Cartilaginous structure will split Arch of into primary bronchi aorta Ascending Aorta #5 Esophagus Between trachea & vertebral Pulmonary column arteries Grant’s atlas, Fig 1.62B  Nerves of the Superior Mediastinum Nerves Vagus Nerve Phrenic nerves Vagus nerves -> recurrent laryngeal nerve Left recurrent laryngeal enters mediastinum, but right doesn’t Recurrent Sympathetic trunk Laryngeal Sympathetic Nerve Trunk  Nerves of the Superior Mediastinum Phrenic ◦ Arises from C3, C4, C5 ◦ Located on lateral sides of the pericardium ◦ Are located anterior to the root of the lung ◦ Sole motor to the diaphragm ◦ 1/3rd of sensory Moore & Dalley: COA4, Fig. 2.70B  Review Phrenic C3 C4 C5 Phrenic Phrenic Pathway of the Phrenic N. Nerves of the Superior Mediastinum Nerves Vagus Nerve Vagus nerves Located posterior to the root of the lung Sympathetic trunk Cardiac & Postsynaptic sympathetic fibers to Pulmonary Sympathetic Plexuses the viscera of the thoracic cavity (heart, lungs, esophagus) pass Trunk through cardiopulmonary (The plexuses are splanchnic nerves to enter the made up of a mix cardiac, pulmonary and of sympathetic & esophageal plexuses parasympathetics)  Review L. Vagus R. Vagus In Carotid sheath with IJV & Common Carotid a. ? Pathway of the Vagus N.  R. Vagus L. Vagus Vagus (green) L. Recurrent R. Recurrent Laryngeal Laryngeal Cardiac Plexus (around arch & (around of aorta) subclavian a.) Pulmonary What does the Plexus recurrent (slow HR, decrease laryngeal nerve force of contraction, do? constrict bronchioles) Intrinsic muscles of Esophageal larynx (except Plexus cricothyroid) Vagus nerves pass posterior to the root of the lung Pathway of the Vagus N. Moving on…. Inferior Mediastinum Inferior Mediastinum – Anterior Inferior Mediastinum: Anterior Loose connective tissue Fat T4 Lymphatic vessels, lymph nodes Branches of the internal thoracic Posterior Middle vessels Thymus (inferior portion) Inferior Mediastinum Grant’s Atlas, Fig 1.25A Inferior Mediastinum –Middle Middle ◦ Pericardium and heart ◦ Great Vessels ◦ Ascending aorta ◦ Pulmonary trunk / arteries ◦ Pulmonary veins Posterior ◦ SVC / IVC Middle ◦ Phrenic nerves Inferior Mediastinum Grant’s Atlas, Fig 1.25A Inferior Mediastinum - Posterior Posterior to pericardium & diaphragm Contains: Main bronchi Vagus nerves Thoracic (descending) aorta Esophagus Azygos venous system Sympathetic trunk Thoracic duct Posterior Mediastinum - Nerves Nerves Vagus Nerve Vagus nerves Cardiac, pulmonary & esophageal plexuses Recurrent Right and left Vagus nerves become Laryngeal anterior & posterior (LARP) Sympathetic Nerve Trunk Sympathetic trunk Cardiopulmonary splanchnics Sympathetic Trunk Vagus Nerve Abdominopelvic splanchnics Greater Splanchnic Abdominopelvic Lesser Splanchnic Splanchnic Least Splanchnic nerves  Posterior Mediastinum – Thoracic Duct Thoracic duct Left Venous Angle Largest lymphatic channel in the body Conveys most lymph from the body to the venous system Lower limbs, pelvic cavity, abdominal cavity, left UE, left side of the thorax, head and neck. (i.e. all the lymph except for that of the right upper quadrant) Thoracic Duct Empties into left venous angle (green structure) (Right lymphatic duct empties into right venous angle)  Thoracic Duct Thoracic duct Lies on anterior aspect of vertebral bodies “Beaded” appearance due to numerous valves Between azygos vn and esophagus The duct (duck) between two gooses “esophagoose & azygoose” Thoracic Duct (green structure)  Posterior Mediastinum – Azygos System Located on each side of vertebral column Forms collateral pathway for Superior vena Accessory SVC & IVC cava hemiazygos v. Right side Azygos vein Azygos Hemiazygos vein Left side Hemiazygos Accessory Hemiazygos  Azygos System Drains blood from the posterior walls of the thorax & abdomen Superior vena Accessory cava hemiazygos v. It communicates with the Azygos vein posterior intercostal veins Hemiazygos vein and vertebral venous plexus Collateral circulation / alternate route to the heart when obstruction of the IVC occurs Pleural Cavity & Lungs  Pulmonary Cavities Thorax is lined with endothoracic fascia Each pulmonary cavity is lined by a pleural membrane (pleura) which reflects on itself to cover the surface of the lungs as well as the pulmonary cavity Parietal Pleura – lines pulmonary cavity Visceral Pleura – lines the lungs Parietal Pleura Outermost layer of pleural sac One continuous membrane Portions are names according to the surface that it lines Costal parietal pleura Mediastinal parietal pleura Diaphragmatic parietal pleura Cervical parietal pleura Parietal Pleura Parietal Pleura costal mediastinal cervical diaphragmatic Visceral Pleura Inner layer of pleural sac Only 1-2 cells thick Adheres to the surface of each lung including the fissures  Pleural Cavity Pleural Cavity Contains pleural fluid Between the 2 layers of pleura 2 Functions Lubricates the pleural surfaces & allows the layers of pleura to slide smoothly over each other during respiration Surface tension provides cohesion that keeps the lung surfaces in contact with the thoracic wall, so when the thoracic wall expands, the lung will expand & fill with air. Like a film of water between two glass plates  Pleural Recesses Lungs fill the pleural cavities during deep inspiration. During quiet inspiration & during expiration, parts of these cavities are not occupied by the lungs so that portions of the parietal pleura are in contact with each other creating a pleura-lined “gutter”. Can be a potential space for fluid accumulation. Cardiomediastinal Recess Costodiaphragmatic Recess The Tracheobronchial Tree Trunk of the tree: Trachea Right and left main bronchi Continued branching: Lobar, segmental, bronchioles Arterial supply branches in similar pattern – lobar arteries, segmental arteries  The Tracheobronchial Tree The Tracheobronchial Tree Main Bronchi Lobar Bronchi Main Bronchi Segmental Bronchi Lobar Bronchi Segmental Bronchi  Vasculature of the Lungs Vasculature of the Lungs Pulmonary Arteries/Veins Pulmonary Lobar Arteries/Veins Arteries/Veins Segmental Arteries/Veins Lobar Arteries/Veins Segmental Arteries/Veins COA Figure 4.37; 8th ed Muscular wall The Tracheobronchial Tree Trachea Carina Airway/passageway to lungs (trunk of the tree) Lies anterior to the esophagus C-shaped rings of hyaline cartilage With muscular wall posteriorly Terminates at sternal angle (T4) Bifurcation into main bronchi Last tracheal cartilage = carina (keel-shaped) Tracheobronchial Tree Main bronchi -> lobar bronchi -> segmental bronchi -> bronchioles 2 Main Bronchi 1 to each lung Continuation of c-shaped cartilaginous rings Lobar Bronchi – supplies each lobe of the lung 2 on the left 3 on the right Right Bronchus Right Bronchus Shorter, straighter and larger in diameter than left Divides into 3 secondary bronchi (lobar) Superior lobe bronchus Middle lobe bronchus Inferior lobe bronchus Left Bronchus Left Bronchus Smaller in diameter but twice as long as right bronchus Passes underneath arch of aorta but then remains anterior to thoracic aorta Divides into 2 secondary bronchi (lobar) Superior lobe bronchus Inferior lobe bronchus Lungs Organs of respiration Function is to oxygenate the blood Light, soft and spongy – fully occupy the pulmonary cavities. (different from cadaveric lungs) Lie free within the pulmonary cavity ◦ Attached only at the root of the lung Spongy, light and have elastic recoil Can recoil to approx. 1/3 their size when the thoracic cavity is opened and surface tension is lost Lungs Each lung has the following: Apex Base 2 or 3 Lobes created by 1 or 2 Fissures 3 surfaces (costal, mediastinal, diaphragmatic) 3 borders: anterior, inferior & posterior Right lung is larger and wider but shorter (liver) Left lung is smaller (heart)  Apex Right Lung Superior Lobe Anterior Border Posterior Border Horizontal Oblique fissure fissure Inferior Mediastinal surface is Middle Lobe shown in these images Lobe Apex Diaphragmatic surface Left Lung Oblique fissure Superior Posterior Border Lobe Anterior Border Inferior Lobe Costal surface on opposite side of mediastinal surface (not shown on picture) Diaphragmatic surface  Hilum of the Lung Hilum of the lung = doorway pulmonary Artery Pulmonary Veins Area in which the structures Bronchial arteries forming the root of the lung enter/exit Bronchus Structures include: Hilum Bronchus Lymph nodes Pulmonary arteries (blue) Pulmonary veins (red) Bronchial arteries Lymphatics Is this a right lung or a left lung?  Right Lung Right Bronchus Hilum of the Lung Right pulmonary Arteries Right Bronchial Artery Right Pulmonary Veins Posterior Pulmonary arteries Border Arise from pulmonary trunk Carry low-oxygen (venous) blood to the lungs for oxygenation (blue in diagram) Left Lung Pulmonary veins Left pulmonary 2 pulmonary veins on each side Artery carry oxygen-rich (arterial) blood Hilum Left Bronchial Anterior to the left atrium of the heart Arteries Border Left Bronchus Left Pulmonary Veins  Bronchial Arteries Bronchial arteries Supply blood to the lower trachea, structures of the root of the lung, supporting tissues of the lung & visceral pleura all the way out to the respiratory bronchioles Right Bronchial Left Bronchial 2 left bronchial arteries to the left lung Artery Arteries 1 right bronchial artery to the right lung Arise directly from the aorta or intercostal artery Bronchial arteries  Innervation of Pleura / Pleural Pain Visceral pleura Insensitive to pain (doesn’t receive nerves for general sensation) Parietal Pleura Extremely sensitive to pain Phrenic nerve C3, 4, 5 Intercostal nerves Irritation of parietal pleura can create local pain or pain that is referred to the dermatomes supplied by the nerve roots of the intercostal or phrenic nerve supplying that area Refers pain to the thoracoabdominal wall and/or root of the neck / shoulder region (C3, 4, 5 dermatomes)*  Innervation of Pleura & Lungs Pleura & Lungs Pulmonary plexuses –located posterior & anterior to the root of the lungs & Cardiac Plexus connect with cardiac plexus Pulmonary Plexus Nerve networks contain parasympathetic (near root of lung) & sympathetic fibers Parasympathetic: presynaptic fibers from Vagus n. (CN X). These fibers synapse with parasympathetic postganglionic nerves in the pulmonary plexuses and along the bronchi Motor to smooth muscle: bronchoconstrictor Sympathetic fibers are postsynaptic fibers (cell bodies were in the sympathetic chain ganglia) Inhibitory to smooth muscle: bronchodilator Lung – Lymph Drainage Bronchopulmonary nodes Lymphatics bronchopulmonary nodes at hilum bronchomediastinal lymph trunks Clinical Correlations Apices of the lungs The cervical pleurae and apices of the lungs pass through the superior thoracic aperture into the region of the neck Located posterior to the inferior attachment of the SCM Therefore, the lungs can be injured with wounds to the base of the neck (*or dry needling in this area*) Resulting in a pneumothorax Pneumothorax = presence of air in the pleural cavity  Pneumothorax Entry of air into the pleural cavity resulting from a penetrating wound of the parietal pleura (bullet, knife wound, rib fracture, dry needle, etc.) Results in collapse of the lung  Pulmonary Collapse Normal lungs in situ remain distended & in contact with thoracic wall (even with an open airway) due to surface tension created by the fluid in the pleural space (between visceral and parietal pleura) If a penetrating wound occurs in the thoracic wall, air will be sucked into the pleural cavity because of the negative pressure & the surface tension keeping the lung adhered to the thoracic wall will be broken, causing the lung to collapse, expelling most of its air because of the inherent elasticity (elastic recoil) of the air sacs that make up the lung https://www.youtube.com/watch?v=Bt0axpDlTd8  Aspiration of foreign bodies Aspiration of food, small objects (coins), etc. Which bronchus do you think more objects get inhaled into? Right main bronchus It is shorter, wider and runs more vertically than the left  Pulmonary Embolism Obstruction of a pulmonary artery by a blood clot, fat globule or air bubble Usually arises from the lower leg (DVT) and passes through the right side of the heart to a lung via a pulmonary artery and block that artery (PE) or one of its branches Results in partial or complete blockage of blood to the lung Results chest pain, difficulty breathing, etc A medium sized embolus may block an artery supplying a bronchopulmonary segment, leading to pulmonary infarct (death of tissue in that area) Can be fatal  Lung Cancer / Pancoast Tumor Cancer near the apex of the lung may involve nerves in the area Phrenic nerve Paralysis of part of diaphragm Recurrent Laryngeal Hoarseness/paralysis of vocal muscles Sympathetic trunk Interruption of the cervical sympathetic trunk Leads to an absence of sympathetic functions on the ipsilateral side of the head Horner’s Syndrome This Photo by Unknown Author is licensed under CC BY-SA-NC Atrial Septal Defects (ASD) Congenital anomaly ◦ Incomplete closure of the oval foramen (foramen ovale) ◦ All babies have this in utero for blood to bypass the lungs ◦ Normally, this closes shortly after birth Large ASD’s allow oxygenated blood from the lungs to be shunted from the left atrium through the ASD into the right atrium This left to right shunt of blood overloads the pulmonary vascular system resulting in hypertrophy of the right atrium, ventricle and pulmonary arteries https://www.cdc.gov/ncbddd/heartdefects/atrialseptaldefect.htmlfo  Myocardial Infarction Coronary artery atherosclerosis and thrombosis are the major causes of MI Artery occluded LAD: 40-50% Right coronary: 30-40% Left circumflex: 15-20% Coronary Bypass Veins or arteries from elsewhere in the patient’s body are grafted to the coronary arteries to improve blood supply. Cardiopulmonary PT QUESTIONS ?