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The Cardiovascular System 12 Chapter

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  • 1. The Cardiovascular System 12 Chapter Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
  • 2. Anatomy of the Heart
    • In the thoracic cavity within the mediastinum
    • Heart functions:
      • Keeps O 2 -poor blood separate from O 2 -rich blood
      • Keeps the blood flowing in one direction
      • Creates blood pressure
      • Regulates the blood supply
  • 3. Anatomy of the Heart
    • The Wall and Coverings of the Heart
      • Pericardium
        • Two-layered serous membrane that encloses the heart
        • Visceral pericardium (epicardium) forms the outer surface of the heart
      • Myocardium
        • Thickest part of heart wall
        • Made of cardiac muscle
      • Endocardium
        • Inner layer of heart
        • Composed of simple squamous epithelium
      • Pericardial fluid
        • Secreted by epicardium and parietal pericardium
        • Reduces friction as the heart beats
      • The coverings of the heart:
        • Protect the heart
        • Confine it to its location
        • Prevent it from overfilling
  • 4. Fig 12.2
  • 5. Anatomy of the Heart
    • Chambers of the Heart
      • Right atrium
        • Receives O 2 -poor blood
        • Vessels that empty into right atrium:
          • Superior vena cava
          • Inferior vena cava
          • Coronary sinus
        • Venous blood leaves right atrium through the an atrioventricular (AV) valve (tricuspid)
          • Directs the flow of blood
          • Prevents backflow
          • Has three cusps
      • Right ventricle
        • Chordae tendineae
          • Fibrous cords connected to the tricuspid valve
          • Connected to the papillary muscle in ventricle
        • Blood passes through the pulmonary semilunar valve into the pulmonary trunk
  • 6. Anatomy of the Heart
      • Left atrium
        • Receives O 2 -rich blood
        • Blood enters atrium through 4 pulmonary veins
        • Blood leaves left atrium through an AV valve (bicuspid or mitral)
      • Left ventricle
        • Forms the apex of the heart
        • Blood leaves the left ventricle through the aortic semilunar valve and enters the aorta
  • 7. Fig 12.3
  • 8. Anatomy of the Heart
    • Operation of the Heart Valves
      • AV valves
        • Normally open
        • When ventricle contracts
          • AV valves shut
          • Papillary muscles contract, preventing valve from reverting into an atrium
      • Semilunar valves
        • Normally closed
        • Contraction of ventricles forces valves open
  • 9. Anatomy of the Heart
    • Heart Sounds
      • First sound, “lub”
        • Heard when ventricles begin to contract
        • AV valves close
        • Lasts longer and has a lower pitch
      • Second sound, “dup”
        • When ventricles relax
        • Semilunar valves close
      • Heart murmurs
        • Due to ineffective, leaky valves
        • Valves do not close properly
        • Allows blood to backflow into atria or ventricles after valves have closed
  • 10. Anatomy of the Heart
    • Coronary Circulation
      • Heart cells are not nourished by the blood in the chambers
      • The left and right coronary arteries branch from the aorta
        • Coronary arteries branch numerous times
        • Heart is encircled by small blood vessels
      • After blood passes through cardiac capillaries it enters the cardiac veins
      • Cardiac veins enter the coronary sinus
      • Coronary sinus enters the right atrium
  • 11. Fig 12.4
  • 12. Physiology of the Heart
    • Conduction System of the Heart
      • Initiates and stimulates contraction of the atria and ventricles
      • Is intrinsic – does not require nervous stimulation
      • Coordinates contraction of atria and ventricles
  • 13. Physiology of the Heart
      • Nodal Tissue
        • Has muscular and nervous characteristics
        • SA (sinoatrial) node – upper posterior wall of the right atrium
          • Initiates the heartbeat
          • Sends out an excitation impulse every 0.85 seconds
          • Pacemaker of the heart
        • AV (atrioventricular) node – base of the right atrium
          • Impulse is delayed
          • Signals the ventricles to contract
        • Atrioventricular bundle (AV bundle)
        • Purkinje fibers
  • 14. Fig 12.5
  • 15. Physiology of the Heart
        • Artificial pacemaker may be implanted if the SA node fails to work properly
        • Heart block – slow beating of the heart due to a damaged AV node
        • Ectopic pacemaker
          • An area other than the SA node that can become the pacemaker
          • May cause an extra beat
          • Caffeine and nicotine can stimulate an ectopic pacemaker
        • Electrocardiogram
          • Electrolyte changes within the myocardium can be detected by electrical recording devices
          • Helps a physician detect and diagnose the cause of an irregular heartbeat (arrhythmias)
  • 16. Physiology of the Heart
      • Cardiac Cycle
        • All events that occur during one heartbeat
        • Systole – contraction of heart muscle
        • Diastole – relaxation of heart muscle
        • Three phases of the cardiac cycle:
          • Phase 1: Atrial Systole
            • Both atria are in systole
            • Ventricles are in diastole
            • Both AV valves are open
            • The semilunar valves are closed
          • Phase 2: Ventricular Systole
            • Both ventricles are in systole
            • The atria are in diastole
            • Semilunar valves are forced open
            • Both AV valves are closed
          • Phase 3: Atrial and Ventricular Diastole
            • Both atria and both ventricles are in diastole
            • Both AV valves are open
            • The semilunar valves are closed
  • 17. Fig 12.6
  • 18. Physiology of the Heart
      • Cardiac Output (CO)
        • Volume of blood pumped out of a ventricle in one minute
        • Average CO is 5,250 ml/minute
        • Dependent on two factors:
          • Heart rate
            • Beats per minute
            • Can be altered by the autonomic nervous system
            • Temperature affects the heart rate
            • Proper electrolytes are needed to keep the heart rate regular
          • Stroke volume
            • Amount of blood pumped by a ventricle each time it contracts
            • Depends on the strength of contraction
            • Influenced by blood electrolyte concentration and the activity of the autonomic nervous system
            • Venous return and difference in blood pressure also affect the strength of contraction
  • 19. Fig 12.7
  • 20. Anatomy of Blood Vessels
    • Vessels function to:
      • Transport blood and its contents
      • Carry out gas exchange
      • Regulate blood pressure
      • Direct blood flow
    • Arteries and Arterioles
  • 21. Anatomy of Blood Vessels
    • Arteries and Arterioles
      • Transport blood away from the heart
      • Thick, strong walls composed of:
        • Tunica interna - endothelium
        • Tunica media – smooth muscle and elastic fibers
        • Tunica externa – outer connective tissue layer
      • Elasticity allows an artery to expand and recoil
      • Arterioles are small arteries
        • Constriction and dilation affect blood distribution and blood pressure
        • Autonomic nervous system regulates the number of arterioles that are contracted
  • 22. Anatomy of Blood Vessels
    • Capillaries
      • Microscopic blood vessels
      • One layer of endothelial cells
      • Site of nutrient and gas exchange
      • Not all capillary beds are in use at the same time
        • Most have a shunt
        • Precapillary sphincters control the entrance of blood into capillaries
  • 23. Fig 12.9
  • 24. Anatomy of Blood Vessels
    • Veins and Venules
      • Return blood to the heart
      • Venules
        • Drain blood from the capillaries
        • Join together to form veins
      • Vein walls are thinner than arterial walls
      • Valves in veins prevent backward flow of blood
      • Varicose veins and phlebitis
        • Varicose veins
          • Abnormal and irregular dilations in superficial veins
          • Hemorrhoids are varicose veins in the rectum
          • Develop when the valves of the veins become weak
        • Phlebitis
          • Inflammation of a vein
          • Thromboembolism can occur
  • 25. Fig 12.8
  • 26. Physiology of Circulation
    • Velocity of Blood Flow
      • Slowest in capillaries
        • Cross-sectional area is at its maximum
        • Allows time for gas and nutrient exchange
      • Blood flow increases as venules combine to form veins
      • Velocity of blood returning to the heart is low compared to that of blood leaving the heart
  • 27. Fig 12.10
  • 28. Physiology of Circulation
    • Blood Pressure
      • The force of blood against blood vessel walls
      • Highest in the aorta
      • Decreases with distance from left ventricle and is lowest in the venae cavae
      • Fluctuates between systolic blood pressure and diastolic blood pressure
      • Mean arterial blood pressure
        • Pressure in the arterial system averaged over time
        • Equals cardiac output x peripheral resistance
          • Increasing CO increases MABP
          • Peripheral resistance is the resistance to flow between blood and the walls of a blood vessel
            • The smaller the blood vessel or the longer the blood vessel the greater the resistance
            • The greater the resistance the higher the blood pressure
  • 29. Fig 12.11
  • 30. Physiology of Circulation
      • Blood pressure and cardiac output
        • The faster the heart rate the greater the cardiac output
        • As cardiac output increases, blood pressure increases
        • The larger the stroke volume, the greater the blood pressure
        • Stroke volume and heart rate increase blood pressure only if the venous return is adequate
  • 31. Physiology of Circulation
        • Venous return depends on:
          • A blood pressure difference
          • The skeletal muscle pump and the respiratory pump
            • Contraction of skeletal muscles compress the walls of veins causing blood to move past a valve
            • During inhalation, thoracic pressure falls and abdominal pressure rises and blood will flow from an area of higher pressure to an area of lower pressure
          • Total blood volume
            • If blood volume decreases, blood pressure falls
            • If blood volume increases, blood pressure rises
  • 32. Fig 12.12
  • 33. Physiology of Circulation
      • Evaluating circulation
        • Pulse
          • Alternating expansion and recoil of arterial walls
          • Can be felt in superficial arteries (pulse points)
            • Radial artery
            • Common carotid
          • Pulse rate normally indicates the rate of the heartbeat
    Fig 12.14
  • 34. Physiology of Circulation
        • Blood pressure
          • Usually measured in brachial artery
          • Sphygmomanometer is an instrument that records pressure changes
          • The blood pressure cuff is inflated until no blood flows through the artery
          • Korotkoff sounds
            • produced when the pressure in the cuff is released and blood begins to hit the arterial walls
            • Systolic pressure
            • When sounds end diastolic pressure is recorded
    Fig 12.15
  • 35. Physiology of Circulation
          • Normal blood pressure is 120/80
            • Higher number is systolic pressure – pressure recorded when the left ventricle contracts
            • Lower number is diastolic pressure – pressure recorded when the left ventricle relaxes
          • Hypertension is high blood pressure
            • When the systolic pressure is 140 or greater
            • When the diastolic pressure is 90 or greater
  • 36. Circulatory Routes
    • Pulmonary circuit
      • Blood from the body collects in the right atrium
      • Blood moves into the right ventricle
      • Right ventricle pumps blood into the pulmonary trunk
      • Blood flows into the pulmonary capillaries in the lungs
      • Blood flows from the lungs through the pulmonary veins and into the left atrium
  • 37. Circulatory Routes
    • Congestive Heart Failure
      • Damaged left side of the heart fails to pump adequate blood
      • Blood backs up in the pulmonary circuit
        • Pulmonary blood vessels have become congested
        • Causes pulmonary edema
      • Indicated by shortness of breath, fatigue, and a constant cough
      • Treatment
        • Diuretics – increase urinary output
        • Digoxin – increases the heart’s contractile force
        • Dilators – relax blood vessels
  • 38. Circulatory Routes
    • Systemic circuit
      • Includes all other arteries and veins of the body
      • Aorta and venae cavae are the major pathways for blood in the systemic circuit
        • Aorta is the largest artery
        • Superior and inferior venae cavae are the largest veins
      • Begins in the left ventricle
      • The left ventricle pumps blood into the aorta
      • Branches from the aorta go to the major body regions and organs
  • 39. Circulatory Routes Table 12.1
  • 40. Fig 12.16
  • 41. Circulatory Routes Table 12.2
  • 42. Fig 12.17
  • 43. Circulatory Routes
    • Special Systemic Circulations
      • Hepatic Portal System
        • Carries venous blood from the stomach, intestines, and other organs to the liver
        • Capillaries of the digestive tract empty into the superior mesenteric and the splenic veins
        • Superior mesenteric and splenic vein join to form the hepatic portal vein
        • Gastric veins empty into the hepatic portal vein
        • Nutrients and wastes diffuse into liver cells
        • The hepatic veins drain the liver and enter the inferior vena cava
  • 44. Fig 12.18
  • 45. Circulatory Routes
      • Hypothalamus-Hypophyseal Portal System
      • Blood Supply to the Brain
        • Anterior and posterior cerebral arteries and the carotid arteries supply the brain with arterial blood
        • Cerebral arterial circle (circle of Willis)
          • The blood vessels form a circle
          • Provides alternate routes for supplying arterial blood to the brain
          • Equalizes blood pressure in the brain’s blood supply
  • 46. Fig 12.19
  • 47. Circulatory Routes
      • Fetal Circulation
        • Four circulatory features not present in adult circulation
          • Foramen ovale
          • Ductus arteriosus
          • Umbilical arteries
          • Ductus venosus
        • Related to the fact that the fetus does not use its lungs
        • Path of blood in the fetus
          • From the right atrium
            • Most blood enters the left atrium via the foramen ovale
            • Blood that has entered the right ventricle and then the pulmonary trunk is shunted to the aorta through the ductus arteriosus
          • Exchange between maternal and fetal blood occurs at the placenta
          • Blood in the umbilical arteries is oxygen poor
          • Blood in the umbilical veins is oxygen rich
            • Enters the ductus venosus
            • The ductus venosus then joins with the inferior vena cava
  • 48. Fig 12.20
  • 49. Effects of Aging
    • Heart
      • Grows larger with age
      • In many middle-aged people, heart is covered by a layer of fat
      • Number of collagenous fibers in the endocardium increases
      • Valves become thicker and more rigid
      • The myocardium loses contractile power and ability to relax
      • Resting heart rate decrease
  • 50. Effects of Aging
    • Arteries
      • Atherosclerosis and arteriosclerosis are common
      • Chances of coronary thrombosis and heart attack increase
      • Occurrence of varicose veins increases
        • Thromboembolism
        • Pulmonary embolism
  • 51. Homeostasis
    • Maintaining blood composition, pH, and temperature
      • Growth factors regulate the manufacture of formed elements in the red bone marrow
      • The digestive system absorbs nutrients into the blood
      • The lungs and kidneys remove metabolic wastes from the blood
      • The kidneys help maintain the pH of blood
      • The blood distributes heat
      • Blood vessels in the skin dilate or constrict in response to changing temperatures
  • 52. Homeostasis
    • Maintaining blood pressure
      • Sensory receptors within the aortic arch detect a decrease in blood pressure
      • The lymphatic system collects excess tissue fluid, which helps regulate blood volume and pressure
      • The endocrine and nervous systems work together to regulate blood pressure
      • Venous return is aided by the muscular and respiratory systems