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    The Cardiovascular System 12 Chapter The Cardiovascular System 12 Chapter Presentation Transcript

    • The Cardiovascular System 12 Chapter Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
    • 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
    • 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
    • Fig 12.2
    • 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
    • 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
    • Fig 12.3
    • 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
    • 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
    • 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
    • Fig 12.4
    • 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
    • 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
    • Fig 12.5
    • 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)
    • 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
    • Fig 12.6
    • 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
    • Fig 12.7
    • 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
    • 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
    • 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
    • Fig 12.9
    • 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
    • Fig 12.8
    • 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
    • Fig 12.10
    • 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
    • Fig 12.11
    • 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
    • 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
    • Fig 12.12
    • 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
    • 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
    • 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
    • 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
    • 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
    • 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
    • Circulatory Routes Table 12.1
    • Fig 12.16
    • Circulatory Routes Table 12.2
    • Fig 12.17
    • 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
    • Fig 12.18
    • 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
    • Fig 12.19
    • 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
    • Fig 12.20
    • 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
    • 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
    • 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
    • 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