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LECTURE OUTLINES & REVIEW QUESTIONS LECTURE OUTLINE: THE HEART Anat25.LORQ.CirculatorySystem:Heart.mguthrie CIRCULATORY SYSTEM: HEART ANATOMY 25 - GUTHRIE OVERVIEW Heart divided into four chambers Two atria (sing. = atrium) Right & left Separated by interatrial septum Receiving chambers Two ventricles Right & left Separated by inteventricular septum Pumping chambers Two pumps in series Right heart Pulmonary circuit pump Atrium Receives systemic venous blood Low in oxygen; high in carbon dioxide SVC (superior vena cava) Capillary beds above diaphragm IVC Capillary beds below diaphragm Coronary Sinus Capillary beds in heart wall Ventricle Pumps blood through lungs Pulmonary trunk arteries capillaries veins Left heart Systemic circuit pump Atrium Receives pulmonary venous blood High in oxygen; low in carbon dioxide Pulmonary veins (four) Ventricle Pumps blood through systemic circuit Aorta arteries capillaries veins Valves ensure one way flow through system. A-V (atrioventricular) valves: atria ventricles Semilunar valves: ventricles arteries page 1 of 10 LECTURE OUTLINES & REVIEW QUESTIONS HEART LOCATION & ORIENTATION Thoracic cavity: Between lungs Rests on central tendon of diaphragm. Most of heart situated to left of midline. Conical in shape Apex: 4th or 5th left intercostal space Base: great vessels Occupies pericardial cavity; flanked by pleural cavities THE MEDIASTINUM (middle wall ) “Space” between lungs in pleural cavities Boundaries: Anterior: sternum Posterior T1-T12 Superior: thoracic inlet Inferior: diaphragm Divisions: Superior, anterior, middle, posterior Major contents: Superior: great vessels, trachea, esophagus Anterior: thymus Middle: Heart & Pericardial cavity Posterior: esophagus, trachea & bronchi, descending aorta, pulmonary arteries & veins PERICARDIA & PERICARDIAL CAVITY Fibrous pericardium: Dense ct, adherent to central tendon of diaphragm Parietal pericardium: Mesothelium + loose ct. = serous membrane (serosa) Visceral pericardium (also called epicardium) Mesothelium + loose ct = serous membrane (serosa) Pericardial cavity: Between visceral & parietal pericardia Contains serous fluid Anat25.LORQ.CirculatorySystem:Heart.mguthrie CIRCULATORY SYSTEM: HEART ANATOMY 25 - GUTHRIE THE HEART WALL Superficial to deep: Epicardium: visceral pericardium Variable amounts of subepicardial fat Myocardium: cardiac muscle Endocardium & subendocardium: endothelium + loose ct HEART EXTERNAL ANATOMY Surfaces & Margins: Surfaces: Base Pulmonary (right & left) Diaphragmatic Anterior Margins: Inferior (acute) & obtuse. Meet at apex Anterior Aspect of Heart In general: ventricles down and to left; atria up and to right More of right heart visible than left heart Auricles = ear-shaped parts of the atria. Anterior interventricular sulcus Separates ventricles. Contains coronary vessels and variable fat Coronary sulcus Separates ventricles from atria; Contains coronary vessels and variable fat Interrupted by pulmonary trunk Great Vessels (right to left): SVC (superior vena cava) top of right atrium IVC (inferior vena cava) bottom of right atrium Ascending aorta leaves left ventricle aortic arch Branches of arch: Brachiocephalic trunk (artery) Left common carotid Left subclavian a. page 2 of 10 LECTURE OUTLINES & REVIEW QUESTIONS CIRCULATORY SYSTEM: HEART Pulmonary trunk leaves right ventricle pulmonary arteries. Right pulmonary artery passes under aortic arch Ligamentum arteriosum: Band of ct between pulmonary trunk & aortic arch. Remnant of fetal ductus arteriosus. Posterior Aspect of Heart More of left heart visible than right Long axes of atria oriented at nearly right angles Right: superior – inferior; left = transverse Posterior interventricular sulcus Separates ventricles. Contains coronary vessels and variable fat Continuous with anterior interventricular sulcus near apex Coronary sulcus Separates ventricles from atria; Contains coronary vessels and variable fat Coronary sinus Expanded vein in part of sulcus below left atrium Collects blood from cardiac veins. Empties into right atrium Great vessels: SVC & IVC right atrium Two left & two right pulmonary veins left atrium Pulmonary trunk divides into pulmonary arteries Right artery passes under arch of aorta on way to right lung HEART INTERNAL ANATOMY Ventricles Separated by interventricular septum Myocardium much thicker than atrial Both have same basic structural characteristics Right Ventricle Right A-V (atrioventricular, tricuspid) valve Controls atrioventricular opening (orifice) Three cusps Chordae tendineae Anat25.LORQ.CirculatorySystem:Heart.mguthrie ANATOMY 25 - GUTHRIE Connective tissue cords attached to free edges of A-V valve Papillary muscles Three nipple-like extensions of myocardium Chordae tendineae attach to their tips Trabeculae carneae Interlacing ridges of myocardium Pulmonary semilunar valve Controls ventricular – pulmonary trunk opening Three crescent-shaped cusps Moderator band Band of myocardium in lower part of ventricle. Stretches between septum and outer wall. Present in right ventricle only. U-shaped blood flow through ventricle Entrance (A-V orifice) and Exit (pulmonary trunk) at the same level. Left ventricle Left A-V (atrioventricular, bicuspid, mitral) valve Controls atrioventricular opening (orifice) Twocusps Chordae tendineae Connective tissue cords attached to free edges of A-V valve Papillary muscles Two nipple-like extensions of myocardium Chordae tendineae attach to their tips Trabeculae carneae Interlacing ridges of myocardium Aortic semilunar valve Controls ventricular – ascending aorta opening U-shaped blood flow Entrance (A-V orifice) and Exit (ascending aorta) at the same level. Myocardium much thicker than right ventricle No moderator band page 3 of 10 LECTURE OUTLINES & REVIEW QUESTIONS CIRCULATORY SYSTEM: HEART ANATOMY 25 - GUTHRIE Atria Separated by interatrial septum (hard to see in most diagrams) Myocardium much thinner than in ventricles Both have same basic structural characteristics Valve flaps or folds are usually called cusps. Composition: connective tissue core covered with endocardium A-V valve cusps are flat sheets with irregular free edges. Semilunar valve cusps resemble half a tea cup Right Atrium Openings: SVC IVC + “valve” “Valve” = crescent-shaped fold of endocardium + ct. Does not open and close. Coronary sinus + “valve” “Valve” = crescent-shaped fold of endocardium + ct. Does not open and close. Atrioventricular orifice + right A-V valve A-V valve cusps Free edges attached to papillary muscles by chordae tendineae Three papillary muscles in right ventricle Two papillary muscles in left ventricle Left are bigger than right Fossa ovalis (oval depression) Oval depression in interatrial septum. Scar left by closure of foramen ovale, a fetal opening between the atria Pectinate muscles Feather-like ridges of myocardium in auricle and adjacent part of atrial wall. Rest of atrial wall is smooth Left Atrium Openings: Pulmonary veins (2 right + 2 left) Atrioventricular orifice + left A-V valve No fossa ovalis Pectinate muscles Feather-like ridges of myocardium in auricle only. Rest of atrial wall is smooth HEART VALVES: A CLOSER LOOK A-V valves guard openings between atria and ventricles Semilunar valves guard openings between ventricles and arteries Anat25.LORQ.CirculatorySystem:Heart.mguthrie Semilunar valves Both valves have three cusps. Dense ct “beak” on free edge Small depressions in arterial wall just above cusps. Facilitates closure. Aortic valve: Openings of coronary arteries above two of the cusps. Fibrous skeleton of heart Connective tissue between atria & ventricles Somewhat resembles interlocking figure 8’s Attachment site for valves + myocardium Valve Function Ensure one-way flow of blood through heart. A-V valves Open: Allows blood flow from atrium to ventricle Closed: Mechanism: Ventricular myocardium contracts. Ventricular pressure increases. Blood pushes on undersides of cusps. Cusps forcesd together. Prevents reflux of blood from ventricles to atria during ventricular pumping phase. page 4 of 10 LECTURE OUTLINES & REVIEW QUESTIONS CIRCULATORY SYSTEM: HEART Prevention of “overclosure” or “blow-back:” Papillary muscles chordae tendineae free edges of cusps Semilunar valves Open: Mechanism: Ventricular myocardium contracts. Ventricular pressure increases. Blood flattens cusps against wall. Allows blood flow from ventricle into artery Closed: Mechanism: Ventricular myocardium relaxes. Ventricular pressure decreases. Ventricular pressure < arterial pressure. Arterial blood ventricle. Valve cusps trap blood, balloon out, make contact. Prevents backflow from arteries to ventricles. FIRST & SECOND HEART SOUNDS First Heart Sound: Often written as “lubb.” Low pitched; softer Closure of A-V valves Second Heart Sound: Often written as “dupp.” High pitched; louder. Closure of semilunar valves Listening to valve sounds on chest wall Aortic: 2nd intercostal space to right of sternum Pulmonic: 2nd intercostal space to left of sternum Tricuspid: 5th intercostal space to right of sternum Bicuspid: 5th intercostal space to left of sternum Anat25.LORQ.CirculatorySystem:Heart.mguthrie ANATOMY 25 - GUTHRIE CORONARY CIRCULATION Part of Systemic Circulation Coronary Arteries: right and left Only branches of ascending aorta First branches of systemic circulation (heart takes care of itself) Run to right or left in coronary sulcus between atria & ventricles In general: Right coronary artery branches supply right heart Left coronary artery branches supply left heart But variable amounts of overlap Major Named Branches (most common pattern; variations occur) Right Coronary Artery: SA Nodal (right atrium toward SVC and S-A node), Right marginal (inferior or acute margin) AV Nodal Posterior interventricular (posterior interventricular sulcus) Left Coronary Artery: Short; divides into: Circumflex (coronary sulcus to back of heart) Left marginal (left or obtuse margin) Posterior left ventricular Anterior interventricular (toward apex in anterior sulcus) Diagonal Cardiac veins: Most empty into coronary sinus right atrium Major Veins: Small (runs with right marginal a.) Middle (runs with posterior interventricular a.) Great (runs with anterior interventricular and circumflex aa.) Posterior vein of left ventricle (runs with posterior left ventricular a.) Anterior cardiac veins right atrium page 5 of 10 LECTURE OUTLINES & REVIEW QUESTIONS CIRCULATORY SYSTEM: HEART Myocardial Infarction Collateral Circulation Alternate circulatory routes Terminal or end arteries Sole supply routes No collateral pathways Functional end arteries Potential collateral routes Not sufficient to compensate for sudden blockage Coronary arteries = functional end arteries Blockage myocardial infarction CARDIAC MUSCLE: A Quick Review Branching cells. Connected end to end by intercalated discs. One or two nuclei/ cell. Striations or bands: A, I, Z. “Myofibrils:” arrays of myofilaments. Lots of mitochondria. Intercalated discs look like projecting interlocking fingers. Transverse parts: Desmosomes Fasciae adherentes (elongated tight junctions) Longitudinal parts: gap junctions (cell to cell communication). EM: Thick & thin myofilaments. Arranged to produce A, I, H, M, Z bands Sarcoplasmic reticulum around myofibrils. More tubular than in skeletal muscle. Meets t-tubules at Z lines. ANATOMY 25 - GUTHRIE Anatomy: S-A (sinu-atrial) node: cluster of cells in right atrial wall adjacent to SVC termination. A-V node: cluster of cells at junction of interatrial and interventricular septa. A-V bundle: Bundle of cells leaving A-V node in upper part of interventricular septum. Splits into: Right and left bundle branches. Travel down interventricular septum to apex, then up outer ventricular walls towards coronary sulcus. (In right ventricle, some bundle branch cells run in moderator band from the interventricular septum to outer wall.) Purkinje fibers branch off and contact some cardiac muscle cells. Function: All parts of system periodically and automatically fire action potentials. But S-A node = “pacemaker” Fires most frequently and drives rest of system. S-A node atrial myocardium (contraction / relaxation) AV node AV bundle right & left bundle branches: purkinje fibers ventricular myocardium (contraction / relaxation) Not necessary to contact all myocardial cells. Gap junctions relay action potential from cell to cell Takes time: Atrial myocardium…interventricular septum to apex… outer ventricular walls to coronary sulcus. Heart contraction ~ wringing out a dishrag. Right heart slightly ahead of left heart. CONDUCTION SYSTEM Specialized heart muscle cells. Assure synchronization of atrial & ventricular filling and pumping. Anat25.LORQ.CirculatorySystem:Heart.mguthrie page 6 of 10 LECTURE OUTLINES & REVIEW QUESTIONS CIRCULATORY SYSTEM: HEART CARDIAC CYCLE: PUMPING SEQUENCE & BLOOD FLOW Diastole and Systole Terms usually refer to ventricular activity Diastole = myocardial relaxation Systole = myocardial contraction The Cycle Diastole: ventricular filling. Atrial & ventricular myocardium relaxed. AV valves open. Semilunar valves closed. Pressure in heart low. Blood flow: SVC, IVC, Coronary sinus right atrium AV orifice past open right AV valve right ventricle Pulmonary veins left atrium AV orifice past open left AV valve left ventricle S-A Node fires atrial myocardium atrial contraction (weak) final volume of blood forced into ventricles atrial relaxation Systole: ventricular contraction AV node: slight delay, then fires AV bundle bundle branches purkinje fibers ventricular myocardia starts to contract ventricular volume starts to decrease intraventricular pressure starts to increase AV valves close (first heart sound; prevent reflux into atria) Action potential continues to spread through ventricular myocardium ventricular volume continues to decrease intraventricular pressure continues to increase semilunar valves open blood forced into pulmonary trunk and ascending aorta (arterial walls expand to take blood; elastic tissue stretched). ANATOMY 25 - GUTHRIE Ventricular myocardium relaxes ventricular volume increases intraventricular pressure decreases arterial pressure higher than ventricular pressure elastic tissue in arterial walls recoils: blood forced toward ventricles semilunar valves close. (2nd heart sound). AV valves open… Cycle repeats. HEART INNERVATION Autonomic Nerves Sympathetic and Parasympathetic Match cardiac rate and output to need. Not necessary for myocardial contraction or synchronization. Myocardial & conduction system automaticity Parasympathetic (“decelerator fibers”) Effects: Decreased heart rate (minor decrease in contractile force + some coronary arterial constriction) Pathway: Medulla: inhibition center neurons dorsal motor nucleus of vagus n. vagus nerves (cranial nerves X) second order neurons S-A and A-V node cells Sympathetic (“accelerator fibers”): Effects: Increased: heart rate, contractile force, cardiac output. Pathway: Medulla: excitatory center neurons first order sympathetic neurons in lateral grey column of thoracic spinal cord thoracic spinal nerves (preganglionic fibers) second order neurons in sympathetic chains sympathetic cardiac nerves (postganglionic fibers) S-A and A-V node cells + myocardial cells Diastole: ventricular relaxation Anat25.LORQ.CirculatorySystem:Heart.mguthrie page 7 of 10 LECTURE OUTLINES & REVIEW QUESTIONS CIRCULATORY SYSTEM: HEART DEVELOPMENT & CONGENITAL DEFECTS Development: “Blood islands” develop in mesoderm (18 day embryo) blood vessels start to form. Two endothelial tubes fuse. Fused tube develops two expansions + arterial and venous ends Heart folds & rotates. Interatrial and interventricular septa form. Great vessels separate Defects: Ventricular septal defect Frequency: ~ 1/500 births Problem: Upper septal deficiency. Result: Blood mixes between ventricles. Transposition of great vessels Frequency: ~ 1/1000 births Problem: Aorta from right ventricle & pulmonary trunk from left ventricle. (Bulbus cordis does not divide properly.) Result: Unoxygenated blood repeats systemic circuit; oxygenated repeats pulmonary circuit. Coarctation of aorta Frequency: ~ 1/1500 births Problem: Part of descending aorta narrowed Result: Increased work load on left ventricle. Tetralogy of Fallot Frequency: ~ 1/2000 births Problem: pulmonary trunk narrowed + pulmonic stenosis + ventricular septal defect + aorta opens connected to both ventricles + right ventricular myocardial thickening (due to overload) Result: ???? Anat25.LORQ.CirculatorySystem:Heart.mguthrie ANATOMY 25 - GUTHRIE Pulmonary stenosis Frequency: ~ 1/2800 births Problem: pulmonic valve narrowed. Result: Decreased blood flow to lungs. REVIEW QUESTIONS: THE HEART 1. The anatomical “wall” between the lungs is called the __?__. (a) pleural cavity (b) peritoneal cavity (c) mediastinum (d) pericardial cavity (e) none of these 2. The heart occupies the __?__ mediastinum. (a) superior (b) anterior (c) posterior (d) middle (e) lateral 3. In its normal position, the apex of the heart is located __?__. (a) to the left of the midline (b) in the fourth or fifth intercostal space (c) in the cardiac notch of the left lung (d) all of these (e) none of these 4. The pericardial cavity is located between the __?__ . (a) myocardium and endocardium (b) parietal and fibrous pericardia (c) epicardium and parietal pericardium (d) myocardium and epicardium (e) none of these 5. The muscle of the heart wall is referred to as __?__. (a) endocardium (b) myoepithelium (c) endothelium (d) myocardium (e) epicardium 6. The heart is lined with __?__. (a) epicardium (b) visceral pericardium (c) endocardium (d) myocardium (e) none of these 7. The coronary sulcus is the external boundary between the __?__ . (a) right and left atria (b) right and left ventricles (c) atria and ventricles (d) right and left auricles (e) none of these page 8 of 10 LECTURE OUTLINES & REVIEW QUESTIONS CIRCULATORY SYSTEM: HEART 8. The anterior and posterior interventricular sulci of the heart __?__. (a) mark the external boundaries between the ventricles (b) overlie the interventricular septum (c) are continuous with each other near the apex of the heart (d) all of these (e) none of these 9. Which of the following is not located in the right atrium ? (a) valve and orifice of the coronary sinus (b) valve and orifice of the IVC (c) openings of the pulmonary veins (d) orifice of the SVC (e) fossa ovalis 10. Pectinate muscles __?__. (a) are interlacing ridges of myocardium (b) are located in the left auricle (c) are located in the right auricle and adjacent atrial wall (d) all of these (e) none of these 11. Blood enters the left atrium through the __?__. (a) pulmonary trunk (b) pulmonary veins (c) inferior vena cava (d) superior vena cava (e) coronary sinus ANATOMY 25 - GUTHRIE 17. Papillary muscles are __?__. (a) projections of myocardium (b) connected to chordae tendineae (c) located in the ventricles (d) contract during systole to control the A-V valves (e) all of these 18. __?__ are interlacing ridges of myocardium located in the ventricles. (a) pectinate muscles (b) papillary muscles (c) trabeculae carneae (d) chordae tendineae (e) none of these 19. Which of the following can be found only in the right ventricle ? (a) papillary muscles (b) trabeculae carneae (c) chordae tendineae (d) moderator band (e) myocardium 20. The aortic semilunar valve is located between the __?__ and the __?__. (a) left ventricle, ascending aorta (b) right ventricle, pulmonary trunk (c) right ventricle, conus arteriosus (d) left ventricle, aortic arch (e) left atrium, left ventricle 12. The right atrium receives blood from the __?__. (a) IVC (b) SVC (c) coronary sinus (d) all of these (e) none of these 21. The pulmonary semilunar valve is located between the __?__ and the __?__. (a) left ventricle, ascending aorta (b) right ventricle, pulmonary trunk (c) right ventricle, conus arteriosus (d) left ventricle, aortic arch (e) left atrium, left ventricle 13. The tricuspid valve is located between the __?__ and the __?__. (a) pulmonary trunk, right ventricle (b) ascending aorta, left ventricle (c) right ventricle, right atrium (d) left ventricle, left atrium (e) right atrium, left atrium 22. During ventricular diastole, the semilunar valves prevent the backflow of blood from the __?__. (a) atria to ventricles (b) ventricles to atria (c) aorta and pulmonary trunk to the ventricles (d) ventricles to the aorta and pulmonary trunk (e) none of these 14. The valve between the left atrium and the left ventricle is called the __?__ . (a) left A-V (b) mitral (c) bicuspid (d) all of these (e) none of these 23. The semilunar valves consist of __?__ cusps. (a) 2 (b) 3 (c) 4 15. The left A-V valve has __?__ cusps (= flaps) and the right A-V valve has __?__. (a) 2, 2 (b) 3, 3 (c) 2, 3 (d) 3, 2 (e) none of these 16. Chordae tendineae __?__. (a) are attached to the free edges of the A-V valves (b) are attached to papillary muscles (c) are located in the ventricles (d) all of these (e) none of these Anat25.LORQ.CirculatorySystem:Heart.mguthrie 24. The fibrous skeleton of the heart is __?__. (a) located between the atria and the ventricles (b) an attachment site for the semilunar and atrioventricular valves (c) is an attachment site for the myocardium (d) all of these (e) none of these 25. Which heart chamber has the thickest myocardium ? (a) left ventricle (b) right ventricle (c) left atrium (d) right atrium page 9 of 10 LECTURE OUTLINES & REVIEW QUESTIONS CIRCULATORY SYSTEM: HEART 26. The right ventricle pumps blood into the __?__. (a) pulmonary trunk (b) pulmonary veins (c) IVC (d) SVC (e) ascending aorta 27. Blood leaves the left ventricle through the __?__. (a) thoracic aorta (b) aortic arch (c) pulmonary trunk (d) ascending aorta (e) abdominal aorta 28. If you traced a volume of blood through the circulatory system beginning at the IVC, through which heart chamber would it pass thirdly ? (a) right ventricle (b) left atrium (c) left ventricle (d) right atrium 29. The first heart sound is caused by the __?__. (a) closure of the semilunar valves (b) opening of the semilunar valves (c) closure of the A-V valves (d) opening of the A-V valves (e) contact of the heart apex with the rib cage 30. The second heart sound is caused by the __?__. (a) closure of the semilunar valves (b) opening of the semilunar valves (c) closure of the A-V valves (d) opening of the A-V valves (e) contact of the heart apex with the rib cage 31. The left coronary artery branches into __?__ arteries. (a) anterior and posterior descending (b) circumflex and posterior descending (c) marginal and circumflex (d) circumflex and anterior descending (e) none of these 32. The right coronary artery terminates as the __?__ artery. (a) marginal (b) anterior interventricular (c) posterior interventricular (d) circumflex (e) nodal 33. The __?__ cardiac vein runs with the posterior interventricular branch of the right coronary artery. (a) small (b) middle (c) great (d) none of these ANATOMY 25 - GUTHRIE 35. Nearly all of the veins draining the heart wall empty into the __?__. (a) SVC (b) IVC (c) coronary sulcus (d) coronary sinus (e) anterior cardiac veins 36. If you traced a volume of blood from the ascending aorta through the right coronary artery, which artery would it be least likely to go through ? (a) circumflex (b) posterior interventricular (c) marginal (d) superior venal caval (nodal) 37. The S-A node of the heart's conduction system __?__. (a) is located in the right atrium (b) is the normal pacemaker of the heart (c) is located near the SVC (d) is connected to the A-V node by internodal tracts (e) all of these 38. The A-V node of the heart's conduction system __?__. (a) is located at the junction of the interatrial and interventricular septa (b) sends impulses into the common A-V bundle (c) is driven by impulses from the S-A node (d) all of these (e) none of these 39. Purkinje fibers __?__. (a) are modified cardiac muscle cells in the heart's conduction system (b) are also called pectinate muscles (c) are also called trabeculae carneae (d) are the same as papillary muscles (e) none of these 40. If you traced an impulse through the heart's conduction system, through which of the following listed structures would it pass thirdly ? (a) Purkinje fibers (b) common A-V bundle (c) S-A node (d) A-V node (e) right and left bundle branches 41. If you traced an impulse through the heart's conduction system, through which of the following listed structures would it pass last ? (a) Purkinje fibers (b) common A-V bundle (c) S-A node (d) A-V node (e) right and left bundle branches 34. The __?__ cardiac vein runs with the anterior interventricular and circumflex branches of the left coronary artery. (a) small (b) middle (c) great (d) none of these Anat25.LORQ.CirculatorySystem:Heart.mguthrie page 10 of 10