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Visual Anatomy & Physiology (Part II) PDF

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The Heart and 19 Cardiovascular Function L e A R n i n G o U tco M e S Section 1 • Structure of the Heart These Learning Outcomes 19.1 Describe the heart’s location, shape, and borders. correspond 19.2 Describe the structure of the pericardium and explain its functions, identify the layers of by number to the heart wall, and describe the structures and functions of cardiac muscle. this chapter’s 19.3 Describe the location and general features of the heart. modules and 19.4 Describe the cardiac chambers and the heart’s external anatomy. indicate what 19.5 Describe the major vessels supplying the heart, and cite their locations. you should be 19.6 Trace blood flow through the heart, identifying the major blood vessels, chambers, and able to do after heart valves. completing 19.7 Describe the relationship between the AV and semilunar valves during a heartbeat. the chapter. 19.8 CLINICAL MODULE Define arteriosclerosis, and explain its significance to health. Section 2 • Cardiac Cycle 19.9 Explain the complete round of cardiac systole and diastole. 19.10 Explain the events of the cardiac cycle, and relate the heart sounds to specific events. 19.11 Describe the components and functions of the conducting system of the heart. 19.12 Describe an action potential in cardiac muscle, and explain the role of calcium ions. 19.13 Describe the factors affecting the heart rate. 19.14 Describe the variables that influence stroke volume. 19.15 Explain how stroke volume and cardiac output are coordinated. 19.16 CLINICAL MODULE Identify the electrical events shown on an electrocardiogram. Section 3 • Coordination of Cardiac Output and Blood Flow 19.17 Explain the effects of pressure, resistance, and venous return on cardiac output. 19.18 Describe the factors that influence total peripheral resistance. 19.19 Describe the factors that determine blood flow. 19.20 Describe the movement of fluids between capillaries and interstitial spaces. 19.21 Explain central regulation, autoregulation, and baroreceptor reflexes in response to changes in blood pressure and blood composition. 19.22 Explain the hormonal regulation of blood pressure and blood volume. 19.23 Describe the role of chemoreceptor reflexes in adjusting cardiovascular activity. 19.24 Explain how the cardiovascular system responds to the Learning Outcomes demands of exercise. are repeated at the 19.25 CLINICAL MODULE Explain the body’s response to bottom of each blood loss. module. 684 M19_MART8949_02_SE_CH19.indd 684 12/4/13 2:48 PM Module 19.1 SECTION 1 • Structure of the Heart The heart has a superior base, an inferior apex, and four borders The base of the heart is at its superior border, where the great veins and arteries are 1 The heart is located near the attached. The base sits anterior chest wall, directly posterior to the sternum at the level of the third costal posterior to the sternum. A mid- sagittal section through the trunk 1 1 cartilage, centered about 1.2 cm (0.5 in.) to the left side. does not divide the heart into equal halves. Note that (1) the 2 2 center of the base lies slightly to the left of the midline, (2) a line 3 3 Ribs drawn between the center of the base and the apex points 4 4 The inferior, pointed tip of the further to the left, and (3) the heart is the free apex (Ā-peks). 5 5 entire heart is rotated to the A typical adult heart measures left around this line, so that the 6 6 approximately 12.5 cm (5 in.) right atrium and right ventricle from the base to the apex, dominate an anterior view of 7 7 which reaches the fifth the heart ( 2 ). 8 intercostal space approxi- 8 mately 7.5 cm (3 in.) to the left 9 9 of the midline. 10 10 2 This anterior view illustrates the Superior border borders of the heart. The base forms the superior border. The right border of the heart is formed by the right atrium. The left border is formed by the left ventricle and a small portion of the left atrium. The left border extends to the apex, where it meets the inferior border. The inferior Right border is formed atrium mainly by the inferior wall of the right Right border Right ventricle. ventricle Left border Module 19.1 Review Inferior border This section examines the anatomy a. The anterior view of the heart is dominated by which structures? of the heart. We will then consider the regulation of cardiac function b. The great veins and arteries are attached to which aspect of the heart? (Section 2) before considering how cardiac and vasomotor activities c. Is the apex located on the superior or inferior aspect of the heart? are coordinated. 19.1 Describe the heart’s location, shape, and borders. 685 M19_MART8949_02_SE_CH19.indd 685 12/4/13 2:48 PM Module 19.2 The heart wall contains concentric 3 This light micrograph shows the histological characteristics that layers of cardiac muscle tissue The Pericardium distinguish cardiac muscle tissue from skeletal muscle tissue: (1) small cell size, The pericardium is the serous Each cardiac muscle cell is membrane that lines the (2) a single, centrally located nucleus, connected to several 1 This is a view of a section taken from the wall pericardial cavity and covers the (3) branching interconnections others at specialized sites heart (Module 4.14, p. 160). between cells, and (4) specialized of the heart and the surrounding pericardium. known as intercalated The heart wall contains three layers: epicardium, intercellular connections. (in-TER-ka-lā-ted) discs. Parietal Pericardium myocardium, and endocardium. The parietal pericardium is the portion of the serous membrane that lines the outer wall of the pericardial cavity. The parietal Cardiac muscle tissue LM × 575 pericardium is reinforced by a dense fibrous layer; together 4 Cardiac muscle cells are found only in the heart. Like skeletal Connective Pericardial cavity they form the pericardial sac muscle fibers, cardiac muscle cells contain organized tissues (contains serous fluid) that surrounds the heart. myofibrils, and the presence of many aligned sarcomeres gives Cardiac muscle cells are relatively the cells a striated appearance. They are almost totally small, averaging 10–20 μm in Dense fibrous layer dependent on aerobic metabolism to obtain the energy they diameter and 50–100 μm in length. Areolar tissue need to continue contracting. The sarcoplasm of a cardiac muscle cell contains many mitochondria and abundant Intercalated Mesothelium disc (sectioned) reserves of myoglobin that store oxygen. Because these cells Myocardium Epicardium are metabolically very active and have a high demand for The myocardium, or muscular oxygen and nutrients, cardiac tissues are richly supplied The epicardium, or visceral Nucleus wall of the heart, forms both atria with capillaries. pericardium, covers the outer and ventricles. This middle layer surface of the heart. This portion contains cardiac muscle tissue, of the serous membrane Mitochondria blood vessels, and nerves. The consists of an exposed mesothe- 5 At an intercalated disc, the plasma membranes of two myocardium consists of concen- lium and an underlying layer of adjacent cardiac muscle cells are extensively intertwined tric layers of cardiac muscle tissue. areolar tissue that is attached to and bound together by gap junctions and desmosomes. These the myocardium. connections help stabilize the positions of adjacent cells. The gap Endocardium junctions allow ions and small molecules to move from one cell to another. Bundles of Mesothelium myofibrils This creates a direct electrical connection between the two muscle cells. An The inner surfaces of the Areolar tissue heart, including those of the Endothelium action potential can travel across an intercalated disc, moving quickly from one thheea retn vdaolvceasr, dairue mco, vae sriemdp bley Areolar tissue H e art wall cfiarrmdliya ca nmcuhsocrleed c etoll tthoe a mnoetmhebrr. aMney oafti bthriel si ninte trhcea ltawteod i ndtisecrl aonckdi ncagn m “puusclll et ocgeelltsh aerre” Idnistecrcalated squamous epithelium and with maximum efficiency. Because the cardiac muscle cells are mechanically, underlying areolar tissue. chemically, and electrically connected to one another, the entire tissue resembles The squamous epithelial a single, enormous muscle cell. For this reason, cardiac muscle has been called a lining of the cardiovascular functional syncytium (sin-SISH-ē-um; a fused mass of cells). system is called an endothe- lium. The endothelium of Gap junction the heart is continuous with the endothelium of the attached great vessels. Intercalated Disc Atrial Z lines bound to musculature 2 The atrial myocardium contains opposing cell membranes muscle bundles that wrap around the atria and form figure-eights that Desmosomes encircle the great vessels. Superficial ventricular muscles wrap around both ventricles; deeper muscle layers spiral around and between the ventricles toward the apex in Ventricular musculature a figure-eight pattern. 686 • Chapter 19: The Heart and Cardiovascular Function M19_MART8949_02_SE_CH19.indd 686 12/4/13 2:48 PM 3 This light micrograph shows the histological characteristics that The Pericardium distinguish cardiac muscle tissue from skeletal muscle tissue: (1) small cell size, The pericardium is the serous Each cardiac muscle cell is membrane that lines the (2) a single, centrally located nucleus, connected to several 1 This is a view of a section taken from the wall pericardial cavity and covers the (3) branching interconnections others at specialized sites heart (Module 4.14, p. 160). between cells, and (4) specialized of the heart and the surrounding pericardium. known as intercalated The heart wall contains three layers: epicardium, intercellular connections. (in-TER-ka-lā-ted) discs. Parietal Pericardium myocardium, and endocardium. The parietal pericardium is the portion of the serous membrane that lines the outer wall of the pericardial cavity. The parietal Cardiac muscle tissue LM × 575 pericardium is reinforced by a dense fibrous layer; together 4 Cardiac muscle cells are found only in the heart. Like skeletal Connective Pericardial cavity they form the pericardial sac muscle fibers, cardiac muscle cells contain organized tissues (contains serous fluid) that surrounds the heart. myofibrils, and the presence of many aligned sarcomeres gives Cardiac muscle cells are relatively the cells a striated appearance. They are almost totally small, averaging 10–20 μm in Dense fibrous layer dependent on aerobic metabolism to obtain the energy they diameter and 50–100 μm in length. Areolar tissue need to continue contracting. The sarcoplasm of a cardiac muscle cell contains many mitochondria and abundant Intercalated Mesothelium disc (sectioned) reserves of myoglobin that store oxygen. Because these cells Myocardium Epicardium are metabolically very active and have a high demand for The myocardium, or muscular oxygen and nutrients, cardiac tissues are richly supplied The epicardium, or visceral Nucleus wall of the heart, forms both atria with capillaries. pericardium, covers the outer and ventricles. This middle layer surface of the heart. This portion contains cardiac muscle tissue, of the serous membrane Mitochondria blood vessels, and nerves. The consists of an exposed mesothe- 5 At an intercalated disc, the plasma membranes of two myocardium consists of concen- lium and an underlying layer of adjacent cardiac muscle cells are extensively intertwined tric layers of cardiac muscle tissue. areolar tissue that is attached to and bound together by gap junctions and desmosomes. These the myocardium. connections help stabilize the positions of adjacent cells. The gap Endocardium junctions allow ions and small molecules to move from one cell to another. Bundles of Mesothelium myofibrils This creates a direct electrical connection between the two muscle cells. An The inner surfaces of the Areolar tissue heart, including those of the Endothelium action potential can travel across an intercalated disc, moving quickly from one thheea retn vdaolvceasr, dairue mco, vae sriemdp bley Areolar tissue H e art wall cfiarrmdliya ca nmcuhsocrleed c etoll tthoe a mnoetmhebrr. aMney oafti bthriel si ninte trhcea ltawteod i ndtisecrl aonckdi ncagn m “puusclll et ocgeelltsh aerre” Idnistecrcalated squamous epithelium and with maximum efficiency. Because the cardiac muscle cells are mechanically, underlying areolar tissue. chemically, and electrically connected to one another, the entire tissue resembles The squamous epithelial a single, enormous muscle cell. For this reason, cardiac muscle has been called a lining of the cardiovascular functional syncytium (sin-SISH-ē-um; a fused mass of cells). system is called an endothe- lium. The endothelium of Gap junction the heart is continuous with the endothelium of the attached great vessels. Intercalated Disc Atrial Z lines bound to 2 The atrial myocardium contains musculature opposing cell Module 19.2 Review membranes muscle bundles that wrap around a. From superficial to deep, name the the atria and form figure-eights that Desmosomes layers of the heart wall. encircle the great vessels. Superficial b. Describe the tissue layers of the ventricular muscles wrap around both epicardium. ventricles; deeper muscle layers c. Why is it important that cardiac tissue spiral around and between the ventricles toward the apex in Ventricular contain many mitochondria and musculature capillaries? a figure-eight pattern. 19.2 Describe the structure of the pericardium and explain its functions, identify the Section 1: Structure of the Heart • 687 layers of the heart wall, and describe the structures and functions of cardiac muscle. M19_MART8949_02_SE_CH19.indd 687 12/4/13 2:48 PM Module 19.3 The heart is located in the mediastinum, and enclosed by the pericardial cavity 1 The position and orientation of the heart Trachea 4 This is a diagrammatic superior view of a partial dissection relative to the major vessels and the ribs, Thyroid gland of the thoracic cavity. The image illustrates the position of the sternum, and lungs can be seen in this anterior First rib (cut) pericardial cavity and the physical relationships among the view. The heart, surrounded by the pericardial components in the mediastinum. sac, sits in the anterior portion of the mediastinum (mē-dē-as-TĪ-num), the Esophagus Posterior region between the two pleural cavities. Base of heart mediastinum The mediastinum also contains the great Aorta (arch vessels, thymus, esophagus, and trachea. Right lung Left lung segment removed) Apex of heart Left pulmonary Diaphragm artery Pericardial sac Right pleural cavity Left pleural (cut) cavity Anterior view of chest cavity Right Left lung lung 2 To visualize the relationship between the Wrist (corresponds Left heart, pericardium, and the pericardial to base of heart) Bronchus pulmonary Inner wall (corresponds of lung vein cavity, imagine pushing your fist toward the to epicardium) center of a large, partially inflated balloon. The balloon represents the pericardium, and your fist Air space (corresponds Right Aortic Pulmonary is the heart. Your wrist, where the balloon folds to pericardial cavity) pulmonary arch trunk back on itself, corresponds to the base of the artery heart, to which the great vessels, the largest Outer wall (corresponds Left atrium veins and arteries in the body, are attached. to parietal pericardium) Right pulmonary vein Left ventricle The air space inside the balloon corresponds Balloon to the pericardial cavity. Superior vena cava Pericardial cavity Epicardium Right atrium 3 The pericardial sac, or fibrous pericardium, The pericardial cavity contains 15–50 mL of surrounds the heart. The pericardial sac pericardial fluid, secreted by the pericardial Right ventricle Pericardial sac consists of a dense network of collagen fibers. membranes. This fluid acts as a lubricant that Anterior mediastinum It attaches to the central tendon of the reduces friction between the opposing surfaces as diaphragm and sternum, and stabilizes the heart beats. Pathogens can infect the peri- Base of heart the position of the heart and associ- cardium, producing the condition pericarditis. ated vessels within the mediastinum. The inflamed pericardial surfaces rub against one As you can see in this image, the heart does not have a lot The parietal pericardium lines its another, producing a distinctive scratching sound of empty space around it—the thoracic cavity is very that can be heard through a stethoscope. inner surface. crowded. Traumatic injuries that damage the pericar- dium or chest wall can result in fluid accumulation within the pericardial cavity, which can restrict the Parietal Pericardium movement of the heart. This condition, called cardiac Cut edge of epicardium Areolar tissue tamponade (tam-po-NĀD; tampon, plug), can also be Mesothelium caused by acute pericarditis. Cut edge of parietal pericardium Fibrous tissue of pericardial sac Fibrous attachment to Apex of heart central tendon of diaphragm 688 • Chapter 19: The Heart and Cardiovascular Function M19_MART8949_02_SE_CH19.indd 688 12/4/13 2:48 PM 1 The position and orientation of the heart Trachea 4 This is a diagrammatic superior view of a partial dissection relative to the major vessels and the ribs, Thyroid gland of the thoracic cavity. The image illustrates the position of the sternum, and lungs can be seen in this anterior First rib (cut) pericardial cavity and the physical relationships among the view. The heart, surrounded by the pericardial components in the mediastinum. sac, sits in the anterior portion of the mediastinum (mē-dē-as-TĪ-num), the Esophagus Posterior region between the two pleural cavities. Base of heart mediastinum The mediastinum also contains the great Aorta (arch vessels, thymus, esophagus, and trachea. Right lung Left lung segment removed) Apex of heart Left pulmonary Diaphragm artery Pericardial sac Right pleural cavity Left pleural (cut) cavity Anterior view of chest cavity Right Left lung lung 2 To visualize the relationship between the Wrist (corresponds Left heart, pericardium, and the pericardial to base of heart) Bronchus pulmonary Inner wall (corresponds of lung vein cavity, imagine pushing your fist toward the to epicardium) center of a large, partially inflated balloon. The balloon represents the pericardium, and your fist Air space (corresponds Right Aortic Pulmonary is the heart. Your wrist, where the balloon folds to pericardial cavity) pulmonary arch trunk back on itself, corresponds to the base of the artery heart, to which the great vessels, the largest Outer wall (corresponds Left atrium veins and arteries in the body, are attached. to parietal pericardium) Right pulmonary vein Left ventricle The air space inside the balloon corresponds Balloon to the pericardial cavity. Superior vena cava Pericardial cavity Epicardium Right atrium 3 The pericardial sac, or fibrous pericardium, The pericardial cavity contains 15–50 mL of surrounds the heart. The pericardial sac pericardial fluid, secreted by the pericardial Right ventricle Pericardial sac consists of a dense network of collagen fibers. membranes. This fluid acts as a lubricant that Anterior mediastinum It attaches to the central tendon of the reduces friction between the opposing surfaces as diaphragm and sternum, and stabilizes the heart beats. Pathogens can infect the peri- Base of heart the position of the heart and associ- cardium, producing the condition pericarditis. ated vessels within the mediastinum. The inflamed pericardial surfaces rub against one As you can see in this image, the heart does not have a lot The parietal pericardium lines its another, producing a distinctive scratching sound of empty space around it—the thoracic cavity is very that can be heard through a stethoscope. inner surface. crowded. Traumatic injuries that damage the pericar- dium or chest wall can result in fluid accumulation within the pericardial cavity, which can restrict the Parietal Pericardium movement of the heart. This condition, called cardiac Cut edge of epicardium Areolar tissue tamponade (tam-po-NĀD; tampon, plug), can also be Mesothelium caused by acute pericarditis. Module 19.3 Review Cut edge of parietal pericardium a. Define mediastinum. Fibrous tissue of pericardial sac b. Describe the heart’s location in the body. Fibrous attachment to Apex of heart c. Why can cardiac tamponade be a life- central tendon of diaphragm threatening condition? 19.3 Describe the location and general features of the heart. Section 1: Structure of the Heart • 689 M19_MART8949_02_SE_CH19.indd 689 12/4/13 2:48 PM Module 19.4 The boundaries between the 2 This view of the posterior surface of the heart shows the left atrium and its chambers of the heart can be connection to the pulmonary veins. It Aortic arch also shows the right atrium and Left pulmonary artery identified on its external surface its connection to the coronary Right pulmonary Left pulmonary veins artery veins and the venae cavae. Superior vena cava 1 The four cardiac chambers can easily be identified in Left a superficial view of the anterior surface of the heart. atrium The two atria have relatively thin muscular walls and are highly Fat and vessels in expandable. When not filled with blood, the outer portion of each the coronary sulcus Right pulmonary veins atrium deflates and becomes a lumpy, wrinkled flap. Shallow (superior and inferior) grooves, or sulci (singular, sulcus), mark the boundaries between the atria and ventricles and between the left and right ventricles. The coronary sinus carries blood collected from the The connective tissue of the epicardium generally contains myocardium by numerous Right substantial amounts of fat, especially along the sulci. In fresh coronary veins and conveys Left atrium or preserved hearts, this fat must be stripped away to expose the blood to the right atrium. ventricle the underlying grooves. These sulci also contain the arteries and veins that carry blood to and from the cardiac muscle. Inferior vena cava Right ventricle The posterior interventricular sulcus is a shallow depression The ligamentum arteriosum on the posterior surface that Aortic arch attaches the pulmonary trunk to the marks the boundary between aortic arch. It is a fibrous remnant of the left and right ventricles. the fetal connection between the aorta and the pulmonary trunk. Ascending aorta Posterior surface Superior vena cava 3 As you see in this anterior view, a Pulmonary trunk dissected heart from a preserved cadaver is not conveniently Left subclavian artery The auricle (AW-ri-kl; auris, color-coded. Auricle of left atrium Left common carotid artery ear) of the atrium is an Right expandable pouch. It has Brachiocephalic trunk atrium this name because it Fat and vessels in the reminded early anatomists anterior interventricular Ligamentum arteriosum of the external ear. sulcus Right Left pulmonary artery Ascending aorta ventricle Pulmonary trunk Superior vena cava Left ventricle Auricle of left atrium The coronary sulcus, a Left coronary artery deep groove, marks the The anterior interventricular border between the atria sulcus is a shallow depression Auricle of right atrium Anterior interventricular and the ventricles. It on the anterior surface that sulcus Right atrium contains fat and vessels. marks the boundary between the left and right ventricles. Right coronary Left Right artery ventricle ventricle Coronary sulcus Anterior Anterior surface Marginal branch interventricular artery of right coronary artery Cadaver dissection, anterior view 690 • Chapter 19: The Heart and Cardiovascular Function M19_MART8949_02_SE_CH19.indd 690 12/4/13 2:48 PM 2 This view of the posterior surface of the heart shows the left atrium and its connection to the pulmonary veins. It Aortic arch also shows the right atrium and Left pulmonary artery its connection to the coronary Right pulmonary Left pulmonary veins artery veins and the venae cavae. Superior vena cava 1 The four cardiac chambers can easily be identified in Left a superficial view of the anterior surface of the heart. atrium The two atria have relatively thin muscular walls and are highly Fat and vessels in expandable. When not filled with blood, the outer portion of each the coronary sulcus Right pulmonary veins atrium deflates and becomes a lumpy, wrinkled flap. Shallow (superior and inferior) grooves, or sulci (singular, sulcus), mark the boundaries between the atria and ventricles and between the left and right ventricles. The coronary sinus carries blood collected from the The connective tissue of the epicardium generally contains myocardium by numerous Right substantial amounts of fat, especially along the sulci. In fresh coronary veins and conveys Left atrium or preserved hearts, this fat must be stripped away to expose the blood to the right atrium. ventricle the underlying grooves. These sulci also contain the arteries and veins that carry blood to and from the cardiac muscle. Inferior vena cava Right ventricle The posterior interventricular sulcus is a shallow depression The ligamentum arteriosum on the posterior surface that Aortic arch attaches the pulmonary trunk to the marks the boundary between aortic arch. It is a fibrous remnant of the left and right ventricles. the fetal connection between the aorta and the pulmonary trunk. Ascending aorta Posterior surface Superior vena cava 3 As you see in this anterior view, a Pulmonary trunk dissected heart from a preserved cadaver is not conveniently Left subclavian artery The auricle (AW-ri-kl; auris, color-coded. Auricle of left atrium Left common carotid artery ear) of the atrium is an Right expandable pouch. It has Brachiocephalic trunk atrium this name because it Fat and vessels in the reminded early anatomists anterior interventricular Ligamentum arteriosum of the external ear. sulcus Right Left pulmonary artery Ascending aorta ventricle Pulmonary trunk Superior vena cava Left ventricle Auricle of left atrium The coronary sulcus, a Left coronary artery deep groove, marks the The anterior interventricular border between the atria sulcus is a shallow depression Auricle of right atrium Anterior interventricular and the ventricles. It on the anterior surface that sulcus Right atrium contains fat and vessels. marks the boundary between the left and right ventricles. Right coronary Left Module 19.4 Review Right artery ventricle ventricle a. Name the four cardiac chambers. Coronary sulcus Anterior b. Name and describe the shallow Anterior surface Marginal branch interventricular depressions and grooves found on the artery of right coronary heart’s external surface. artery c. Which structures collect blood from the myocardium, and into which heart Cadaver dissection, anterior view chamber does this blood flow? 19.4 Describe the cardiac chambers and the heart’s external anatomy. Section 1: Structure of the Heart • 691 M19_MART8949_02_SE_CH19.indd 691 12/4/13 2:48 PM Module 19.5 Coronary Arteries The heart has an extensive blood supply Aortic The heart works continuously, so cardiac muscle cells require reliable arch supplies of oxygen and nutrients. Although a great volume of blood 3 This view identifies the flows through the chambers of the heart, the myocardium needs its own, major collecting vessels on Left separate blood supply. The coronary circulation supplies that blood to the the anterior surface of the heart. atrium muscle tissue of the heart. During maximum exertion, blood flow to the myocardium may increase to nine times that of resting levels. The great cardiac vein begins on the Right anterior surface of the ventricles, along 1 The left and right coronary arteries originate at the base of atrium the interventricular sulcus. This vein Left Coronary Artery the ascending aorta, where blood pressure is the highest in Pulmonary drains blood from the region supplied the systemic circuit. However, myocardial blood flow is not trunk The left coronary by the anterior interventricular steady: It peaks while the heart muscle is relaxed, and almost Aaorrcthic artery supplies The anterior cardiac veins, Right artery. The great cardiac vein reaches ceases while it contracts. blood to the left which drain the anterior surface ventricle Left the level of the atria and then curves ventricle, left atrium, of the right ventricle, empty ventricle around the left side of the heart within Left and interventricular directly into the right atrium. the coronary sulcus to empty into the atrium septum. coronary sinus. Circumflex artery Right Anterior view Right Coronary Artery atrium The large anterior interventricular (left The right coronary artery, which follows the coronary sulcus around the heart, supplies blood to the right atrium, portions Right aanrtteerriyo rru dness caelonndgin g) 4 This view identifies the major of both ventricles, and portions of the conducting system of ventricle Left collecting vessels on the posterior the surface within the heart, which contols and coordinates the heartbeat. ventricle surface of the heart. the anterior interventricular Great Marginal arteries from the right coronary artery supply sulcus. Left cardiac vein the surface of the right ventricle. atrium Anterior view The coronary sinus is an expanded vein that opens into the right atrium near the base Right 2 Branches of the left and right coronary arteries Arterial anastomoses between the of the inferior vena cava. Left atrium The small cardiac vein receives blood continue onto the posterior surface of the heart. anterior and posterior interventricular ventricle from the posterior surfaces of the right arteries maintain a fairly continuous atrium and ventricle. It empties into the The circumflex artery is a branch of the blood flow despite pressure fluctua- coronary sinus along with the middle left coronary artery that curves to the left tions in the left and right coronary The posterior cardiac cardiac vein. around the coronary sulcus, eventually arteries. vein drains the area Right meeting and fusing with small branches supplied by the ventricle of the right coronary artery. A marginal circumflex artery. The middle cardiac vein, draining artery branches from the circumflex the area supplied by the posterior artery to supply the posterior surface Left Posterior view interventricular artery, empties into atrium of the left ventricle. the coronary sinus. Marginal artery Each time the left ventricle contracts, it forces blood into the Right Left atrium The right coronary artery continues across aorta. The arrival of additional blood at elevated pressures ventricle the posterior surface of the heart, supply- stretches the elastic walls of the aorta. When the left ing the posterior interventricular ventricle relaxes, pressure decreases, and the walls of the (posterior descending) artery, which runs toward the apex within the posterior aorta recoil. This recoil, called elastic rebound, pushes Right interventricular sulcus. This vessel supplies blood both forward, into the systemic circuit, and backward, ventricle blood to the interventricular septum and into the coronary arteries. Thus, the combination of blood Right coronary adjacent portions of the ventricles. pressure and elastic rebound ensures a continuous flow of artery blood to meet the demands of active cardiac muscle tissue. Posterior view 692 • Chapter 19: The Heart and Cardiovascular Function M19_MART8949_02_SE_CH19.indd 692 12/4/13 2:48 PM

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2nd Edition. - Pearson Education, 2014. — 503 p.sual Anatomy & Physiology combines a visual approach with a modular organization to deliver an easy-to-use and time-efficient book that uniquely meets the needs of today’s students–without sacrificing the comprehensive coverage of A&P topics requ
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