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19 PART 1

19 PART 1. The Heart Pages 562-580. The Heart. A muscular double pump Pulmonary circuit —takes blood to and from the lungs Systemic circuit —vessels transport blood to and from body tissues Atria —receive blood from the pulmonary and systemic circuits

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19 PART 1

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  1. 19 PART 1 The Heart Pages 562-580

  2. The Heart • A muscular double pump • Pulmonary circuit—takes blood to and from the lungs • Systemic circuit—vessels transport blood to and from body tissues • Atria—receive blood from the pulmonary and systemic circuits • Ventricles—the pumping chambers of the heart

  3. Figure 19.1 The heart as a double pump. Pulmonary Circuit Capillary bedsof lungs wheregas exchangeoccurs Aorta andbranches Pulmonaryarteries Left atrium Pulmonaryveins Right atrium Heart Right ventricle Left ventricle Systemic Circuit Venaecavae Capillarybeds of allbody tissueswhere gasexchangeoccurs Oxygen-rich,CO2-poor blood Oxygen-poor,CO2-rich blood

  4. Location and Orientation within the Thorax • Heart—typically weighs 250–350 grams (healthy heart) • Largest organ of the mediastinum • Located between the lungs • Apex lies to the left of the midline • Base is the broad posterior surface

  5. Superior vena cava Midsternal line Aorta Parietal pleura (cut) Rib 2 Pulmonary trunk Left lung Pericardium (cut) Apex of heart Diaphragm Diaphragm (c) (a) Mediastinum Mediastinum Aorta Superior vena cava Heart Left lung Right auricle of right atrium Right lung Fat in epicardium Rib 5 Right ventricle Pericardium (cut) Posterior (b) Apex of heart (d) Location of the Heart in the Thorax Figure 19.2

  6. Structure of the Heart—Coverings • Pericardium—two primary layers • Fibrouspericardium • Strong layer of dense connective tissue • Serous pericardium • Formed from two layers • Parietal layer of the serous pericardium • Visceral layer of the serous pericardium

  7. Pericardium Myocardium Pulmonary trunk Fibrous pericardium Parietal layer of serous pericardium Pericardial cavity Epicardium (visceral layer of serous pericardium) Heart wall Myocardium Endocardium Heart chamber Layers of the Pericardium and of the Heart Wall Figure 19.3

  8. Structure of the Heart—Layers of the Heart Wall • Epicardium • Visceral layer of the serous pericardium • Myocardium • Consists of cardiac muscle • Muscle arranged in circular and spiral patterns • Endocardium • Endothelium resting on a layer of connective tissue • Lines the internal walls of the heart

  9. Heart Chambers • Right and left atria • Superior chambers • Right and left ventricles • Inferior chambers • Internal divisions • Interventricular septum • Interatrial septum

  10. Aorta Left pulmonary artery Superior vena cava Left atrium Right pulmonary artery Left pulmonary veins Pulmonary trunk Right atrium Mitral (bicuspid) valve Right pulmonary veins Fossa ovalis Aortic valve Pectinate muscles Pulmonary valve Tricuspid valve Left ventricle Right ventricle Papillary muscle Chordae tendineae Interventricular septum Trabeculae carneae Epicardium Inferior vena cava Myocardium Endocardium (e) Frontal section Heart Chambers Figure 19.5e

  11. Right Atrium • Forms right border of heart • Receives blood from systemic circuit • Superior vena cava • Inferior vena cava • Coronary sinus • Right auricle projects anteriorly from superior corner of atrium • Opens into right ventricle via tricuspid valve (right atrioventricular valve)

  12. Left common carotid artery Brachiocephalic trunk Left subclavian artery Aortic arch Superior vena cava Ligamentum arteriosum Right pulmonary artery Left pulmonary artery Ascending aorta Left pulmonary veins Pulmonary trunk Auricle of left atrium Right pulmonary veins Circumflex artery Right atrium Left coronary artery (in coronary sulcus) Right coronary artery (in coronary sulcus) Anterior cardiac vein Left ventricle Right ventricle Great cardiac vein Right marginal artery Anterior interventricular artery (in anterior interventricular sulcus) Small cardiac vein Inferior vena cava (b) Anterior view Apex Gross Anatomy of the Heart Figure 19.5b

  13. Aorta Superior vena cava Right pulmonary artery Left pulmonary artery Right pulmonary veins Left pulmonary veins Right atrium Auricle of left atrium Left atrium Inferior vena cava Great cardiac vein Coronary sinus Right coronary artery (in coronary sulcus) Posterior vein of left ventricle Posterior interventricular artery (in posterior interventricular sulcus) Left ventricle Middle cardiac vein Right ventricle Apex (d) Inferior view; surface shown rests on the diaphragm. Inferior View of the Heart Figure 19.5d

  14. Aorta Left pulmonary artery Superior vena cava Left atrium Right pulmonary artery Left pulmonary veins Pulmonary trunk Right atrium Mitral (bicuspid) valve Right pulmonary veins Fossa ovalis Aortic valve Pectinate muscles Pulmonary valve Tricuspid valve Left ventricle Right ventricle Papillary muscle Chordae tendineae Interventricular septum Trabeculae carneae Epicardium Inferior vena cava Myocardium Endocardium (e) Frontal section Heart Chambers Figure 19.5e

  15. Right Ventricle • Receives blood from right atrium through the tricuspid valve • Pumps blood into pulmonary circuit via • Pulmonary trunk • Internal walls of right ventricle • Trabeculae carneae • Papillary muscles • Chordae tendineae • Pulmonary semilunar valve • Located at opening of right ventricle and pulmonary trunk

  16. Left Atrium • Makes up heart’s posterior surface • Receives oxygen-rich blood from lungs through pulmonary veins • Opens into the left ventricle through • Mitral valve (left atrioventricular valve)

  17. Aorta Superior vena cava Right pulmonary artery Left pulmonary artery Right pulmonary veins Left pulmonary veins Right atrium Auricle of left atrium Left atrium Inferior vena cava Great cardiac vein Coronary sinus Right coronary artery (in coronary sulcus) Posterior vein of left ventricle Posterior interventricular artery (in posterior interventricular sulcus) Left ventricle Middle cardiac vein Right ventricle Apex (d) Inferior view; surface shown rests on the diaphragm. Inferior View of the Heart Figure 19.5d

  18. Left common carotid artery Brachiocephalic trunk Left subclavian artery Aortic arch Superior vena cava Ligamentum arteriosum Right pulmonary artery Left pulmonary artery Ascending aorta Left pulmonary veins Pulmonary trunk Auricle of left atrium Right pulmonary veins Circumflex artery Right atrium Left coronary artery (in coronary sulcus) Right coronary artery (in coronary sulcus) Anterior cardiac vein Left ventricle Right ventricle Great cardiac vein Right marginal artery Anterior interventricular artery (in anterior interventricular sulcus) Small cardiac vein Inferior vena cava (b) Anterior view Apex Gross Anatomy of the Heart Figure 19.5b

  19. Aorta Left pulmonary artery Superior vena cava Left atrium Right pulmonary artery Left pulmonary veins Pulmonary trunk Right atrium Mitral (bicuspid) valve Right pulmonary veins Fossa ovalis Aortic valve Pectinate muscles Pulmonary valve Tricuspid valve Left ventricle Right ventricle Papillary muscle Chordae tendineae Interventricular septum Trabeculae carneae Epicardium Inferior vena cava Myocardium Endocardium (e) Frontal section Heart Chambers Figure 19.5e

  20. Left Ventricle • Forms apex of the heart • Internal walls of left ventricle • Trabeculae carneae • Papillary muscles • Chordae tendineae • Pumps blood through systemic circuit via • Aortic semilunar valve (aortic valve)

  21. Aorta Superior vena cava Right pulmonary artery Left pulmonary artery Right pulmonary veins Left pulmonary veins Right atrium Auricle of left atrium Left atrium Inferior vena cava Great cardiac vein Coronary sinus Right coronary artery (in coronary sulcus) Posterior vein of left ventricle Posterior interventricular artery (in posterior interventricular sulcus) Left ventricle Middle cardiac vein Right ventricle Apex (d) Inferior view; surface shown rests on the diaphragm. Inferior View of the Heart Figure 19.5d

  22. Aorta Left pulmonary artery Superior vena cava Left atrium Right pulmonary artery Left pulmonary veins Pulmonary trunk Right atrium Mitral (bicuspid) valve Right pulmonary veins Fossa ovalis Aortic valve Pectinate muscles Pulmonary valve Tricuspid valve Left ventricle Right ventricle Papillary muscle Chordae tendineae Interventricular septum Trabeculae carneae Epicardium Inferior vena cava Myocardium Endocardium (e) Frontal section Heart Chambers Figure 19.5e

  23. Heart Valves—Valve Structure • Each valve composed of • Endocardium with connective tissue core • Atrioventricular (AV) valves • Between atria and ventricles • Aortic and pulmonary valves • At junction of ventricles and great arteries

  24. Pulmonary valve Aortic valve Area of cutaway Mitral valve Myocardium Tricuspid valve Tricuspid (right atrioventricular) valve Mitral (left atrioventricular) valve Aortic valve Pulmonary valve Fibrous skeleton Anterior (a) Heart Valves—Valve Structure Figure 19.6a

  25. Fibrous Skeleton • Surrounds all four valves • Composed of dense connective tissue • Functions • Anchors valve cusps • Prevents overdilation of valve openings • Main point of insertion for cardiac muscle • Blocks direct spread of electrical impulses

  26. Blood returning to the heart fills atria, putting pressure against atrioventricular valves; atrioventricular valves are forced open. 1 Direction of blood flow Atrium Cusp of atrioventricular valve (open) 2 As ventricles fill, atrioventricular valve flaps hang limply into ventricles. Chordae tendineae Papillary muscle Ventricle 3 Atria contract, forcing additional blood into ventricles. (a) AV valves open; atrial pressure greater than ventricular pressure Function of the Atrioventricular Valves Figure 19.7a

  27. 1 Ventricles contract, forcing blood against atrioventricular valve cusps. Atrium Cusps of atrioventricular valve (closed) 2 Atrioventricular valves close. 3 Papillary muscles contract and chordae tendineae tighten, preventing valve flaps from everting into atria. Blood in ventricle (b) AV valves closed; atrial pressure less than ventricular pressure Function of the Atrioventricular Valves Figure 19.7b

  28. Aorta Pulmonary trunk As ventricles contract and intraventricular pressure rises, blood is pushed up against semilunar valves, forcing them open. (a) Semilunar valves open As ventricles relax and intraventricular pressure falls, blood flows back from arteries, filling the cusps of semilunar valves and forcing them to close. (b) Semilunar valves closed Function of the Semilunar Valves Figure 19.8

  29. Heart Sounds • “Lub-dup”—sound of valves closing • First sound “lub” • The AV valves closing • Second sound “dup” • The semilunar valvesclosing

  30. Pulmonary valve Aortic valve Area of cutaway Mitral valve Myocardium Tricuspid valve Tricuspid (right atrioventricular) valve Mitral (left atrioventricular) valve Aortic valve Pulmonary valve Fibrous skeleton Anterior (a) Heart Sounds Figure 19.6a

  31. Pathway of Blood Through the Heart • Beginning with oxygen-poor blood in the superior and inferior venae cavae • Go through pulmonary and systemic circuits • A blood drop passes through all structures sequentially • Atria contract together • Ventricles contract together

  32. Pulmonary semilunar valve Tricuspid valve Superior vena cava (SVC) Inferior vena cava (IVC) Coronary sinus Right ventricle Pulmonary trunk Right atrium Pulmonary trunk SVC Coronary sinus Tricuspid valve Right atrium Pulmonary semilunar valve IVC Right ventricle Oxygen-poor blood returns from the body tissues back to the heart. Two pulmonary arteries carry the blood to the lungs (pulmonary circuit) to be oxygenated. To heart To lungs Pulmonary arteries Oxygen-rich blood Oxygen-poor blood Oxygen-rich blood is delivered to the body tissues (systemic circuit). Oxygen-rich blood returns to the heart via the four pulmonary veins. To body To heart Aorta Pulmonary veins Mitral valve Aortic semilunar valve Left atrium Left ventricle Aortic semilunar valve Mitral valve Four pulmonary veins Left ventricle Left atrium Aorta Blood Flow Through the Heart Figure 19.10

  33. Heartbeat • 70–80 beats per minute at rest • Systole—contraction of a heart chamber • Diastole—expansion of a heart chamber • Systole and diastole also refer to • Stage of heartbeat when ventricles contract and expand

  34. Left ventricle Right ventricle Interventricular septum Structure of Heart Wall • Walls differ in thickness • Atria—thin walls • Ventricles—thick walls • Systemic circuit • Longer than pulmonary circuit • Offers greater resistance to blood flow • Left ventricle—three times thicker than right • Exerts more pumping force

  35. Cardiac Muscle Tissue • Forms a thick layer called myocardium • Striated like skeletal muscle • Contractions pump blood through the heart and into blood vessels • Contracts by sliding filament mechanism • Cardiac muscle cells • Short • Branching • Have one or two nuclei

  36. Nucleus Intercalated discs Cardiac muscle cell Gap junctions Fasciae adherens Cardiac muscle cell Mitochondrion Intercalated disc Nucleus (a) Mitochondrion T tubule Sarcoplasmic reticulum Z disc Nucleus Sarcolemma (b) I band A band I band Microscopic Anatomy of Cardiac Muscle Figure 19.12

  37. Cardiac Muscle Tissue • Cells join at intercalated discs • Complex junctions • Form cellular networks • Cells are separated by delicate endomysium • Binds adjacent cardiac fibers • Contains blood vessels and nerves

  38. Cardiac Muscle Tissue • Intercalated discs—complex junctions • Adjacent sarcolemmas interlock • Possess two distinct regions • Fasciae adherens-bind adjacent cells together & transmit contractile force to them • Gap junctions-allow ions to pass between cells & transmission of signals to adjacent cells

  39. Cardiac Muscle Tissue • Triggered to contract by Ca2+ entering the sarcoplasm • Signals sarcoplasmic reticulum to release Ca2+ ions • Ions diffuse into sarcomeres • Trigger sliding filament mechanism

  40. Conducting System • Cardiac muscle tissue has intrinsic ability to • Generate and conduct impulses • Signal these cells to contract rhythmically • Conducting system • A series of specialized cardiac muscle cells • Sinoatrial (SA) node sets the inherent rate of contraction

  41. Superior vena cava Right atrium 1 The sinoatrial (SA) node (pacemaker) generates impulses. Internodal pathway Left atrium 2 The impulses pause (0.1 sec) at the atrioventricular (AV) node. Purkinje fibers 3 The atrioventricular (AV) bundle connects the atria to the ventricles. Inter- ventricular septum 4 The bundle branches conduct the impulses through the interventricular septum. 5 The Purkinje fibers stimulate the contractile cells of both ventricles. Conducting System Figure 19.14

  42. Dorsal motor nucleus of vagus The vagus nerve (parasympathetic) decreases heart rate. Cardioinhibitory center Cardio- acceleratory center Medulla oblongata Sympathetic trunk ganglion Thoracic spinal cord Sympathetic trunk Sympathetic cardiac nerves increase heart rate and force of contraction. AV node SA node Parasympathetic fibers Sympathetic fibers Interneurons Innervation • Heart rate is altered by external controls • Nerves to the heart include • Visceral sensory fibers • Parasympathetic branches of the vagus nerve • Sympathetic fibers—from cervical and upper thoracic chain ganglia Figure 19.15

  43. Blood Supply to the Heart • Functional blood supply • Coronary arteries • Arise from the aorta • Main branches • Left and right coronary arteries

  44. Aorta Pulmonary trunk Superior vena cava Left atrium Anastomosis (junction of vessels) Superior vena cava Left coronary artery Right atrium Great cardiac vein Circumflex artery Anterior cardiac veins Right coronary artery Left ventricle Coronary sinus Right ventricle Right marginal artery Anterior interventricular artery Posterior interventricular artery Small cardiac vein Middle cardiac vein (b) The major cardiac veins (a) The major coronary arteries Blood Supply to the Heart Figure 19.16

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