Heart Internal Structure and Surface Anatomy PDF

The Heart: Internal and surface anatomy Fraser Chisholm [email protected] Learning Outcomes After this lecture, time spent in the dissecting room, and further private study you should be able to: 1. Describe the margins and surfaces of the heart 2. Describe the morphological features of the c...

The Heart: Internal and surface anatomy Fraser Chisholm [email protected] Learning Outcomes After this lecture, time spent in the dissecting room, and further private study you should be able to: 1. Describe the margins and surfaces of the heart 2. Describe the morphological features of the cardiac valves 3. Describe the surface anatomy of the heart and its valves in relation to patient examination and the interpretation of radiographs 4. Explain why points of auscultation of heart sounds are different from the surface projection of the heart valves 5. Describe the functional anatomy of the chambers of the heart 6. Explain the functional importance and position of the fibrous skeleton of the heart 7. Explain the clinical significance of papillary muscles and chorda tendinea 8. Identify cardiac borders on chest x-ray and other anatomical structures on medical images 2 Circulation • Pulmonary circulation – Right heart pumps deoxygenated blood to the lungs – Low pressure: 12 – 16 mmHg • Systemic circulation – Left heart pumps oxygenated blood throughout the body – High pressure: 70 – 120 mmHg • Therefore, require two separate sides, each with a chamber to receive and one to pump 3 Heart Surfaces 4 Heart Surfaces Sternocostal (anterior) Diaphragmatic (inferior) • Right ventricle • Left ventricle • Right atrium • Left ventricle • Right ventricle • Separated from the base of heart by the coronary sinus R Pulmonary • Right Atrium L Pulmonary • Left Ventricle •Cardiac impression 5 Heart surfaces Base (posterior) • Left Atrium and pulmonary veins Apex • Left 5th intercostal Mid-clavicular line • Right atrium • Fixed posteriorly to the pericardium, at the level of T6(5)-T9(8) vertebrae • More superior and lateral in children 6 Heart Margins – important for imaging • Right margin: – Right atrium • Left margin: – Left ventricle and left auricle • Inferior margin – Right ventricle + left ventricle 7 Septa and Chambers • • Interatrial (IA) septum Interventricular (IV) septum • Atrioventricular (AV) septum • • Right (RA) and left (LA) atria Right (RV) and left (LV) ventricles ➢ Right Atrium + Right Ventricle = Right heart ➢ Left Atrium + Left Ventricle = Left Heart 8 Atria Right • • • Forms most of the right margin of the heart Atrium proper (w/smooth surface) + auricle (w/ridges) Superior v. cava (SVC), inferior v. cava (IVC), coronary sinus (CS) and anterior cardiac vv. Left • Forms most of the base of the heart • Atrium proper (w/smooth surface) + auricle (w/ridges) • 4x pulmonary veins 9 Atrial Tributaries • Opening of SVC – Deep to the joint between right 3rd costal cartilage and sternum – No valve inside SVC – Intervenous tubercle (foetus) • Opening of IVC – Valve of inferior vena cava • Opening of coronary sinus – Valve of coronary sinus prevent regurgitation of blood • Openings of anterior cardiac veins Left Atrium • Pulmonary veins – No valves 10 Atrial walls Right • Crista terminalis separates right atrium from right auricle • Fossa ovalis − On the right side of IA septum − Site of foramen ovale of the foetal heart Left Falx septi − Depressed area on the left side of IA septum − Caused by the fusion of valve of foramen ovale − Not at the same level as foramen ovale 11 Auricles • Ridged inner surface, formed by pectinate muscles • Provide some power of contraction without significantly thickening the cardiac wall 12 Ventricles Right • • • • Behind sternum Sits on central tendon of diaphragm Wall thickness 3-4 mm. Max. systolic pressure of 30mmHg Left • Left border and Apex • Wall thickness 8-12mm • Max. (normal) systolic pressure of 120mmHg 13 Septa and Chambers Parasternal long axis view Taken from Robert Humphries’ “Basic Echo Cardiography” teaching 14 Septa and Chambers Parasternal short axis view Taken from Robert Humphries’ “Basic Echo Cardiography” teaching 15 Septa and Chambers Apical 4 chamber view Taken from Robert Humphries’ “Basic Echo Cardiography” teaching 16 Septa and Chambers Subcostal view Taken from Robert Humphries’ “Basic Echo Cardiography” teaching 17 Atrio-Ventricular valves • • • • Right Left Tricuspid valve 3 Cusps, attached to anulus fibrosus Blood flows anteriorly and medially Deep to inferior right Sternum • Mitral valve (bicuspid) • 2 Cusps, attached to anulus fibrosis • Blood flows towards the apex of the heart • Deep to left inferior strerum 18 Chordae tendinea • Fibrous chords that extend between papillary muscles and AV valve cusps • Prevent eversion of cusps and therefore: prevent regurgitation of blood into the atria during ventricular systole • Chorda tendinea from one papillary muscle attach to more than one cusp 19 Ventricular outflow tracts Left Right • Infundibulum (conus arteriosus) • Leads to pulmonary trunk • Blood flows upwards, backwards and to the left side through this valve • • • • Aortic Vestibule Posterior to infundibulum Leads to the aorta Blood flows upwards, backwards and to the right side through this valve 20 Semilunar valves Left Right • Pulmonary Valve • 3 cusps • Ant, Left, Right • Nodule at each apex • Aortic valve • 3 cusps • Post, Left, Right • Nodule at each apex 21 Pulmonary and Aortic Sinuses Right • 3 pulmonary sinuses behind the cusps • Fill during diastole to close the valve Left • 3 aortic sinuses (of Valsalva) • Left, Right and non-coronary • Origins of Left and Right Coronary arteries • Fill during diastole 22 Fibrous skeleton of the heart • Heart has a structural support frame formed by a complex set of fibrous rings with connecting areas • Provides a great amount of structural and functional support • 4 fibrous rings (anulus fibrosus) around AV, aortic and pulmonary valves • Between the four rings are two trigones (right and left) and the membranous portions of the IA, IV, and AV septa 23 Fibrous skeleton of the heart • Serves as origin/ insertion for atrial and ventricular muscles • Points of attachment for the cusps • Maintains the patency and integrity of AV and semilunar orifices • Serves as origin/insertion for atrial and ventricular muscles • Insulates the atria from the ventricles • Allows independent atrial and ventricular contraction • Atrioventricular bundle of His should be the only conduction between them (otherwise arrhythmias) 24 Cardiac wall 25 Cardiac wall 26 Muscles of the Ventricles • Morphologically there are 2 or 3 types of muscles on ventricle walls 1. Trabecula carnea: Numerous irregular muscular ridges 2. Papillary muscles - Three (usually!) in the right; 2 in the left ventricle - Named relative to their position - Contract before ventricular contraction 27 Muscles of the Ventricles 3. Septomarginal trabecula (moderator band) − Only in RV − Bridge between interventricular septum and anterior papillary muscle − Carries right bundle branch of AV bundle of cardiac conduction system 28 Cardiac Auscultation • The valves open and close due to changes in blood pressure and cause “sounds” when they close • Closure of AV valves causes 1st heart sound (S1): Start of systole • Closure of semilunar valves causes 2nd heart sound (S2): Start of diastole • Sitting or recumbent position, inspiration, expiration, Valsalva manoeuvre, exercise can cause changes in heart sounds 29 Surface anatomy 1: Right 3rd costal cartilage 2 cm right of the midline 2: Right 6th costal cartilage 2 cm right of the midline 4 1 2 3 3: Left 5th interspace– 7-9 cm left of the midline 4: Left 2nd costal cartilage (interspace) – 3 cm left of the midline 30 Surface anatomy: Valves 31 Cardiac auscultation 1st Heart Sound • Tricuspid valve (S1): Best heard just to the left of the lower part of the sternum near the 4th/ 5th intercostal space • Mitral valve (S1): Best heard over the apex of the heart in the left 5th intercostal space at the midclavicular line • 2nd Heart Sound • Aortic valve (S2): Best heard over the medial end of the right 2nd intercostal space • Pulmonary valve (S2): Best heard over the medial end of the left 2nd intercostal space 32 33 Chest X-ray 34 Chest X-ray 35 Chest Imaging Kelley Fig. 6.4 36