Thorax II Mediastinum & Heart PDF

FOCA 2023 Thorax II Mediastinum & Heart Dr. Mark Hankin Professor & Senior Anatomist Director, Anatomical Sciences Education Center [email protected] 1 Disclosures & Conflicts of Interest Authorship Anatomy & Physiology Revealed v4 2019, McGraw-Hill Clinical Anatomy: A Case Study Approach 2013, McGraw...

FOCA 2023 Thorax II Mediastinum & Heart Dr. Mark Hankin Professor & Senior Anatomist Director, Anatomical Sciences Education Center [email protected] 1 Disclosures & Conflicts of Interest Authorship Anatomy & Physiology Revealed v4 2019, McGraw-Hill Clinical Anatomy: A Case Study Approach 2013, McGraw-Hill Test Prep for the USMLE® – Clinical Anatomy Q&A 2019, Thieme Medical Publishers If you have used any of these resources, I hope you found them helpful. 2 Session Objectives 1. Describe the mediastinum, including its boundaries and contents. 2. Describe the pericardial sac, including its composition and contents. 3. Describe the anatomy of the heart, including its chambers, valves, neurovasculature, anatomical relationships, and surface anatomy. 4. Describe the great vessels and related structures 5. Describe the posterior mediastinum and structures located within or that pass through this compartment. 3 MEDIASTINUM The “Stuff” in the Middle 4 Thoracic Cavity has Two Pleural Cavities & One Mediastinum Pleural cavities Lateral compartments lined by parietal plura serousmembrane fluid Mediastinum porited asl riser secriting Central compartment contains all other thoracic structures Heart & great vessels Trachea Esophagus Thymus Thoracic duct & lymph nodes Sympathetic trunk (chain) 5 Mediastinum Mediastinum divided into superior and inferior parts by the transverse thoracic plane Passes through sternal angle and T4/T5 intervertebral disc containsthe Superior mediastinum aorticarch Sternal angle Transverse thoracic plane of part pereira Anterior mediastinum Inferior mediastinum is subdivided Anterior mediastinum Between sternum and pericardial sac n Vx Middle mediastinum Represented by pericardial sac and its contents (heart & roots of great vessels) aortatplumtruck Middle mediastinum Heart Posterior mediastinum aorta esophagus I Posterior mediastinum Between pericardium, diaphragm and T5-T12 vertebrae 6 PERICARDIUM & PERICARDIAL SAC 7 Pericardial Sac – A Fibroserous Membrane Fibrous pericardium Fibrous serous fluidsecreting External layer: tough & fibrous anchor heart Parietal serous pericardium in chestcavity Serous pericardium Serous fluid permits heart to move freely within sac Two layers Parietal serous pericardium lines inner surfaces of ng of fibrous pericardium Visceral serous pericardium vernet on the heart (epicardium) & roots of great vessels Its Fibrous pericardium B 808 Visceral serous pericardium Gilroy, Thieme Atlas of Anatomy 3e, Fig. 9.6A Fed parietalpericardial green riserapericardium blue fibrouspericardium 8 Pericardial Sinuses Transverse pericardial sinus SVC Ascending aorta Posterior to ascending aorta & pulmonary trunk Usually only one can enter Pulmonary trunk Traverse pericardial sinus (opening) Oblique pericardial sinus Recess (cul-de-sac /deadend) posterior to heart Between left atrium and pulmonary veins Enter (several fingers) from inferior Oblique pericardial sinus (dead-end) IVC 9 Transverse Pericardial Sinus: Clinical Significance Clinical Application Cross-clamping ascending aorta & pulmonary trunk at the transverse pericardial sinus allows surgeon to apply a temporary ligature, and then divert circulation to cardiopulmonary bypass machine. ECA 5e, Clinical Box Fig. B1.11 10 Pericardium & Posterior Mediastinum Esophagus & its nerve plexus lie posterior to the pericardial cavity 11 Cardiac Tamponade Accumulation of blood, fluid, pus, gas, or benign or malignant neoplastic tissue within the pericardial cavity Clinical Application Can occur rapidly or gradually, but eventually results in impaired cardiac output Incremental increase in intrapericardial volume raises intrapericardial pressure, which affects heart function → Prevents full expansion of heart, which limits the amount of blood the heart can receive, and thereby reduces cardiac output 6500metersperminus volumeofbloodheart min Rx: Pericardiocentesis Left 5th or 6th ICS, near the sternum (infrasternal angle) 12 I I THE HEART & ITS CHAMBERS 13 Three Layers of Heart Wall Epicardium Visceral serous pericardium Myocardium Cardiac muscle fibers Endocardium (endothelium) Lines inner cavities & covers heart valves 14 Cardiac Muscle is Arranged in Spiral & Circular Bundles Heart muscle contracts with a wringing motion, which reduces the distance between the base and apex (acts like a rag you would ring out to remove water) Rohen, Color Atlas of Anatomy 7e Quora.com Orientation of Heart As with a pyramid, the base is opposite the apex Apex: @ 5th ICS, in the midclavicular line Base: Posterior (mainly left atrium) Base t behind3rd cogttraage Base Apex SthICS Apex 16 Surface & Borders Four surfaces 1. Anterior (sternocostal) – RV 2. Inferior (diaphragmatic) – mostly LV (RV) 3. Right (pulmonary) – RA 4. Left (pulmonary) – LV Four borders 1. 2. 3. 4. Right (RA) Left (LV) Inferior (RV) Superior (auricles) 17 Sulci (grooves) of the Heart Sulci (grooves) on heart surfaces mark divisions between atria & ventricles Main blood vessels of the heart run in sulci I Coronary sulcus marks division of atria & varthite ventricles between Interventricular sulci (A&P) mark position of interventricular septum betweenthe ventricles I Schuenke, Atlas of Anatomy v2 2e Right Atrium Auricle = atrial appendage Pectinate muscles Openings Inflow: SVC & IVC, and coronary sinus Outflow: Right AV (tricuspid) orifice Other features Interatrial septum with fossa ovalis (remnant of fetal foramen ovalis) Pectinate muscles wenotaorta Crista terminalis SVC Auricle Crista terminalis Right AV (tricuspid) valve Yi Fossa ovalis leftoverfrom development IVC lowerbody Pectinate muscles in auricles Papillary muscles & trabeculae carneae in ventricles Opening of coronary sinus circulation 19 Right Ventricle Openings Pulmonary valve Inflow: Tricuspid (right AV) orifice Outflow: Pulmonary trunk Other features O Interventricular septum Trabeculae carneae, including septomarginal trabecula (moderator 3raveflaps band) Papillary muscles & chordae Anterior papillary muscle tendineae Valves Pectinate muscles in auricles Papillary muscles & trabeculae carneae in ventricles – Tricuspid (right AV) valve w/cordae tendineae A little Latin fun: ! – Pulmonary valve Trabeculae carneae: tra bec’ u lee car’ nee ee Septomarginal trabecula (moderator band) O Chordae tendineae: cor’ dee ten din’ ee ee 20 Left Atrium Openings Inflow: Pulmonary veins Outflow: Mitral/bicuspid (left AV) orifice Left ventricle Left atrium Other features Interatrial septum Pectinate muscles dividesright left aorta fossaord is located Left atrium, with a bit of right atrium, forms base of heart Pectinate muscles in auricles Papillary muscles & trabeculae carneae in ventricles LA RA 21 Left Ventricle Openings Inflow: Left atrioventricular (AV) orifice Outflow: Aortic orifice Other features Interventricular (IV) septum Trabeculae carneae (only in ventricles) Papillary muscles & chordae tendineae Valves: – Left AV (bicuspid, mitral) valve (w/chordae tendineae) – Aortic valve Anterior papillary m. Trabeculae carneae IV septum Posterior papillary m. Mitral valve Chordae tendineae A little Latin pronunciation fun: ! Trabeculae carneae: tra bec’ u lee car’ nee ee Cordae tendineae: cor’ dee ten din’ ee ee 22 Anterior Thoracic Wall and Heart Chambers Landmarks Right atrium lies to the right of sternum and forms the right border of the heart. Right ventricle lies behind and immediately left of the sternum. It forms the inferior border of the heart. Left ventricle forms the apex (5th ICS, ~ 9 cm from the median plane). It forms most of the left border and diaphragmatic surface of the heart. Left atrium lies on the posterior side of the heart and forms most of the base of the heart. 23 d yah g Esophagus Lies Posterior to the Left Atrium Mitral valve insufficiency Clinical Application Blood regurgitated through mitral valve can lead to a dilated left atrium, which can cause heart arrhythmia or failure Symptom of enlarged left atrium is dysphagia terribleshaw oiling 24 Test your Understanding A 23-year-old man is admitted to the ED with a penetrating, anterior chest wound from an ice pick in the 5th ICS, immediately left of the sternum (*). Which structure is most likely damaged due to entry of the ice pick at this site? A. B. C. D. E. O Aortic arch Left atrium Left ventricle Right atrium Right ventricle 25 HEART VALVES Texas Heart Institute www.texasheart.org 26 Fibrous Skeleton of Heart Collagenous rings anchor myocardium & valve cusps, and help keep valve orifices patent (open) Anterior Additional functions Scaffold & passageway for conducting system fibers Electrical insulation between atria & ventricles, so they contract independent of one another posterior Schuenke, Thieme Atlas of Anatomy 2e Vol 2, Fig. 12.6B 27 Heart Valves Anterior Atrioventricular (AV) valves Pulmonary valve Tricuspid A 3 cusps: Anterior, posterior & septal Bicuspid (mitral) LCA L RCA R Right L Left A P 2 cusps: Anterior & posterior S Semilunar valves Pulmonary Aortic valve R A P Tricuspid AV valve P 3 cusps: Anterior, left & right Aortic 3 cusps: Posterior, left & right view from above Bicuspid AV (mitral) valve Posterior Schuenke, Thieme Atlas of Anatomy 2e Vol 2, Fig. 12.6A Superior view Anterior Left Pulmonary valve Right Posterior A Pulmonary valve L R LCA Aortic valve RCA L Aortic valve Bicuspid (mitral) valve R P Tricuspid valve 29 Flow thru Heart Valves Mitral valve AV valves Papillary muscles contract before ventricular contraction Tightens chordae tendineae (tendinous cords), which are attached to more than one cusp Result: pulls cusps together AND prevents their prolapse Semilunar valves Blood ejected from ventricles forces cusps apart Backflow of blood in aorta closes valves and causes filling of coronary arteries To Aortic valve Auscultation of the Heart Valves Midclavicular line Blood carries sounds produced by valves in the direction of blood flow Mnemonic: All Physicians Take Money Aortic: 2nd ICS, right parasternal P A Pulmonary: 2nd ICS, left parasternal Tricuspid: 5th ICS, left parasternal Mitral: 5th ICS, left midclavicular line T M 31 HEART VASCULATURE 32 Coronary Arteries Superior view Coronary arteries originate from aortic sinuses (i.e., behind left & right aortic valve cusps) Right coronary artery (RCA) arises from right aortic sinus (i.e., behind right aortic cusp) Left coronary artery (LCA) arises from left aortic sinus (i.e., behind left aortic cusp) Anterior Aortic sinus Aortic valve LCA Aortic sinus L R RCA P Left Right Posterior 33 Schuenke, Thieme Atlas of Anatomy 2e Vol 2, Fig. 12.6A Coronary Arteries SVC Right coronary artery (RCA) RCA SA nodal (SA) Right (acute) marginal (RMA) Posterior descending (PDA) – 70% of the time LA LCA CX SA RA CX LMA Left coronary artery (LCA) Circumflex (CX) - Left (obtuse) marginal (LMA) - Posterior descending (PDA) – 20% of the time Left anterior descending (LAD) DIA PDA IVC LAD LV RV RMA Potential anastomosis between LAD & PDA 34 Origin of PDA Determines Heart Dominance 35 Why are Coronary Arteries So Important? Both arteries supply heart muscle, but… Left coronary artery Supplies anterior 2/3 of septum via LAD, including AV bundle branches of conducting system LAD also supplies apex of heart (of His) O Right coronary artery Supplies posterior 1/3 of septum via PDA, including AV node 36 Occlusion of Coronary Arteries ‚ 30-40% 2 1 3 Clinical Application 3 1 ƒ 15-20%  40-50% tosoiicomefrom car Sites –ƒ are responsible for 85% of all occlusions Transverse (axial) CT showing diffuse sclerosis in LCA and its circumflex (LCX) and anterior interventricular (LAD) branches Schuenke, Thieme Atlas of Anatomy 2e Vol 2, Fig. 12.17D 37 Coronary artery bypass graft uses a segment of artery or vein to bypass a blocked segment of a coronary artery LIMA (LITA) RIMA (RITA) Clinical Application Left internal thoracic (mammary) artery (LITA or LIMA) is most commonly used, still attached to its origin from subclavian artery This is now a standard for coronary bypass grafting: over time, PTs with LITA→LAD grafts are less likely to die, or need reoperation, compared to PTs who received only vein grafts 38 Cardiac Veins Cardiac veins drain into coronary sinus, which empties into right atrium Cardiac veins parallel branches of coronary arteries Vein Travels with artery Great cardiac Left anterior descending (LAD) Middle cardiac Posterior descending (PDA) Small cardiac Right (acute) marginal (from RCA) 39 Coronary sinus Left auricle Aorta Great cardiac v. Pulmonary trunk Circumflex br. Left atrium Right atrium LAD SA nodal br. RCA Right ventricle Left ventricle RCA Great cardiac v. Which sulcus? PDA Middle cardiac v. Right marginal (acute) a. Which sulcus? ANTERIOR Which sulcus? POSTERIOR Is this heart left or right dominant? Where is the LCA? Name the sulci (grooves) on the heart. 40 Test your Understanding Blockage of which artery would lead to ischemia of the apex of the heart? A. Anterior interventricular (LAD) O B. Circumflex branch of left coronary C. Anterior interventricular (PDA) t D. Right marginal E. Right coronary posterior interarentriculer 41 CARDIAC CONDUCTION & HEART INNERVATION Heart Health: Pacemakers and Death Van de Graaf 2011 CHIhealth.com 42 Cardiac Conducting Fibers Are Modified Cardiac Muscle Cells In Walls of Atria & Ventricles SA node located anterolaterally, at junction of SVC & right atrium Impulses from SA node → AV node AV node located in interatrial septum, near opening of coronary sinus Impulse pathway from AV node: → Common AV bundle (of His) → Bundle branches (R&L) → Purkinje fibers → Ventricle walls contractionof ventricles Anterior view 1 d D pathway SVC D Interatrial septum Interventricular septum Fossa ovalis Opening of coronary sinus 43 2 Location of SA node: junction of SVC & right atrium Aorta PT SVC SVC Aorta PT Right atrium Right ventricle Right atrium Right ventricle 44 Innervation of the Heart Parasympathetics (cholinergic) Preganglionic: brainstem via CN X Postganglionic: intramural ganglia Function: Slows heart rate & force of contraction, constricts coronary arteries Sympathetics (adrenergic) Preganglionic: T1-T4(T6) spinal cord Postganglionic: cervical and superior thoracic sympathetic ganglia Function: Increases heart rate & force of contraction, dilates coronary arteries parasympathic IHR O O THR 45 Cardiac Nerves & Cardiac Plexus Carries nerve fibers TO/FROM heart Location Anterior to tracheal bifurcation and on ascending aorta, aortic arch & pulmonary trunk Autonomic fibers nerve Preganglionic parasympathetics vagus carrythismotor Postganglionic sympathetics O functi n qqq Visceral afferent (sensory) fibers Pain fibers follow sympathetic fibers Reflexive fibers follow vagal fibers motor sensory 46 Cardiac Referred Pain During an MI, pain fibers (visceral afferents) are stimulated by cardiac ischemia Clinical Application Pain fibers from heart follow sympathetic fibers…their cell bodies are in T1-T4 DRGs Somatic sensory cells bodies in the same DRGs…but their fibers project to T1-T4 dermatomes Both groups of sensory fibers synapse in T1-T4 spinal cord & project to brain…which interprets pain from heart as referred pain from T1-T4 dermatomes nipples 47 Cardiac Symptoms in Women & Men Men & women share “typical” cardia symptoms (severe chest pain, cold sweats, pain in left arm) However, women more likely to have subtle, less recognizable symptoms: Neck, jaw, shoulder, upper back, or upper abdominal discomfort Shortness of breath Pain in one or both arms Nausea or vomiting Sweating Lightheadedness or dizziness Unusual fatigue Heartburn (indigestion) Mechanism underlying this difference is not understood, but it is important to consider a wide range of symptoms for cardiac ischemia 48 Test your Understanding Pain from the heart is transmitted by visceral afferent fibers. Where are the cell bodies for these pain fibers? A. C3-C5 dorsal root ganglia B. Dorsal horn of spinal cord 5 C. Inferior vagal ganglia D. Intramural ganglia E. T1-T4 dorsal root ganglia 49 GREAT VESSELS & OTHER STRUCTURES IN THE MEDIASTINUM Patrick Lynch, Radiopaedia.org, rID: 36358 50 Great Vessels Great vessels are in middle mediastinum & superior mediastinum Aorta & its major branches – Brachiocephalic trunksuppliestheupperarm – Left common carotid artery – Left subclavian artery Pulmonary trunk → left & right pulmonary arteries poor inorg from blood noted longs Brachiocephalic veins Superior vena cava Gilroy, Thieme Atlas of Anatomy 3e, Fig. 9.6B 51 Aorta & Pulmonary Trunk Important relationships I Lower edge of aortic arch lies at sternal angle (transthoracic plane) Aortic arches over the root of lung, on the left side of the trachea Transthoracic plane Descending aorta runs posterior to the esophagus Pulmonary trunk lies to the left of the ascending aorta; it divides into left & right pulmonary arteries moret anterior Left pulmonary artery arches over left main bronchus 52 Aorta & Pulmonary Trunk Lower edge of aortic arch lies at sternal angle (transthoracic plane) Aortic arches over the root of lung, on the left side of the trachea Descending aorta runs posterior to the esophagus Pulmonary trunk lies to the left of the ascending aorta; it divides into left & right pulmonary arteries Left pulmonary artery arches over left main bronchus Ligamentum arteriosum between left pulmonary artery to aortic arch (embryologic ductus arteriosum allows maternal oxygenated blood to bypass lungs) Sternal angle Gilroy, Thieme Atlas of Anatomy 3e, Fig. 9.2B 53 Brachiocephalic Veins Brachiocephalic veins form the SVC Posterior to right 1st costal cartilage, at the sternal angle Left brachiocephalic vein I E th Sternal angle Usually >2 longer than right brachiocephalic vein Anterior to origins of three major branches of aortic arch: - Brachiocephalic trunk - Left common carotid - Left subclavian aorta arteries Gilroy, Thieme Atlas of Anatomy 3e, Fig. 9.2B 54 Phrenic & Vagus Nerves & the Root of the Lung Phrenic nerve contrIphreym Phrenic n. Lies ANTERIOR to the root of the lung Vagus n. Vagus nerve behindtheheart Lies POSTERIOR to the root of the lung Root of lung I 55 Nerves in Posterior Mediastinum Vagus n. Vagus nerves (CN X) Supply heart, lungs, esophagus & abdominal organs Vagal branches enter esophageal plexus. Inferiorly, they form anterior & posterior vagal trunks before passing thru diaphragm Recurrent laryngeal nerves – Left: passes under aortic arch Cardiac plexus Left recurrent laryngeal n. Pulmonary plexus Sympathetic trunk & paravertebral ganglia Esophageal plexus Greater splanchnic n. (T5-T9) – Right: passes under subclavian artery Prevertebral ganglia Anterior vagal trunk allapart ofthere nerve Nerves in Posterior Mediastinum Sympathetic trunks & paravertebral ganglia Adjacent to vertebral bodies Rami communicantes convey fibers to/from ganglia Abdominopelvic splanchnic nerves Greater, lesser & least splanchnicsasset nerves supply abdominal organs Cardiac plexus sympore sym On tracheal bifurcation, ascending aorta, aortic arch & pulmonary trunk Vagus n. Cardiac plexus Pulmonary plexus Rami communicantes Greater splanchnic n. (T5-T9) Pulmonary plexus sym pore sym Extension of the cardiac plexus on bronchial tree Left recurrent laryngeal n. Prevertebral ganglia Sympathetic trunk & paravertebral ganglia Esophageal plexus Anterior vagal trunk Sympathetic Innervation of the Body Wall All preganglionic sympathetic cell bodies are in T1-L2(L3) spinal cord White rami communicantes Beforeganglia Convey presynaptic fibers FROM spinal nerve TO paravertebral ganglia – fibers synapse in these ganglia! Gray rami communicantes Spinal nerve lateral gray nom Dorsal ramus spigerve É Postganglionic cell body in ganglion y Preganglionic cell bodies T1-L2(L3) spinal cord tgang t Gray ramus communicans in White ramus communicans After gang line Convey postsynaptic fibers FROM paravertebral ganglia back TO spinal nerve and into dorsal & ventral rami Targets: ion ir ct t ns co Sweat glands Arrector pili Vascular smooth m. Ventral ramus Posterior Mediastinum Thoracic aorta Posterior intercostal aa. Esophageal aa. Accessory hemi-azygos Azygos venous system Left: Hemi-azygos & accessory hemi-azygos vv. Azygos Right: Azygos vein Hemi-azygos Posterior intercostal vv. Esophageal vv. 59 The Thoracic Duct Size Diameter: 2-4 mm Length: 38-45 cm (14-17") Azygos v. Appearance Esophagus Aorta Resembles a small vein…but wo/blood (“white-ish”) May appear “wiggly” Thoracic duct Azygos v. Thoracic duct Aorta Location Anterior to vertebral bodies & posterior to the esophagus Left-Right: Between azygos vein & thoracic aorta Rohen, Color Atlas of Human Anatomy 60 Test your Understanding Which of the following nerves carry postganglionic sympathetic fibers? What are the targets of these fibers? A. Dorsal rami B. Intercostal somatic C. Phrenic somatic D. Radial somatic E. Vagus pong 61 END 62