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Cardiovascular SystemThe Heart
The Heart – what it is…• A muscular double pump each with a flow circuit– Pulmonary circuit – Systemic circuit
• The chambers of the double pump– Atria
• receive blood from the pulmonary and systemic circuits
– Ventricles• the main pressure generating chambers of the heart
Location and Orientation within the Thorax
• Physical Characteristics of the Heart – Size:
• 12 cm. in length• 8 to 9 cm. in width (at widest part)
• 6 cm. in thickness – Weight:
• ♀ 230 ‐ 280 grams• ♂ 280 ‐ 340 grams
• Largest organ of the mediastinum
Location landmarks of the Heart
• Superior right– at costal cartilage
of third rib and sternum
• Inferior right– at costal cartilage
of sixth rib lateralto the sternum
• Superior left– at costal cartilage
of second rib lateral to the sternum
• Inferior left– lies in the fifth intercostal space at the midclavicular line
The Pericardium• Pericardium
– Fibrous pericardium• strong layer of dense irregular connective tissue
– Serous pericardium (two layers)• Superficial layer = parietal serous pericardium• Deep layer = visceral serous pericardium or the epicardium
The Heart Wall
• Epicardium– visceral layer of the serous pericardium
• Myocardium– consists of cardiac muscle– Muscle arranged in circular and spiral patterns
– Muscle in chambers differ in thickness• Endocardium
– endothelium resting on a layer of connective tissue
– Lines the internal walls of the heart
Comparison of ventricle myocardium
• Left ventricle –three times thicker than right– Exerts more pumping force
– Flattens right ventricle into a crescent shape
Key Landmarks on the Heart
• Base
• Apex
• Ventral
• Dorsal
Ventral View of Heart
Posterior/Inferior View of Heart
Heart Chambers
Right Atrium
Right Ventricle
Left Atrium
Left Ventricle
Systemic & Cardiac Circulation
Right Atrioventricular
Valve*
Pulmonary Valve*
Aortic Valve*
Left Atrioventricular
Valve*
Pathway of Blood Through the Heart
• Begin oxygen‐poor blood in the superior and inferior venae cavae and the coronary sinus
Right Atrium
Right Ventricle
Pulmonary Arteries
Pulmonary Trunk
Left Atrium
LungsPulmonary Veins
AortaLeft Ventricle
*Alternate Names exist for these valves!
Heart Chambers
Right Atrium
Right Ventricle
Left Atrium
Left Ventricle
Heart Valves – Valve Structure
• Each valve composed of: – Endocardium with connective tissue core– Surrounded by a fibrous skeleton of dense irregular connective tissue that
• Anchors valve cusps• Prevents over dilation of valve openings• Main point of insertion for cardiac muscle• Blocks direct spread of electrical impulses
• Atrioventricular (AV) valves – between atria and ventricles
• Aortic and pulmonary valves – at junction of ventricles and great arteries
Heart Valves – Valve Structure
Function of the Atrioventricular Valves
Figure 18.9a
Function of the Atrioventricular Valves
Figure 18.9b
Isovolumetric Ventricular Contraction
Function of the Semilunar Valves
Heart Beat & Sounds
• Heart rate of 70‐80 beats/minute at rest• Period of contraction = systole• Period of relaxation = diastole• “Lub‐dup” – sound of valves closing• First sound “lub” – the AV valves closing
– During isovolumetric ventricular contraction• Second sound “dup” – the semilunar valves closing– During isovolumetric ventricular relaxation
Heart Sounds• Each valve sound –best heard near a different heart corner– Pulmonary valve –superior left corner
– Aortic valve –superior right corner
– Mitral (bicuspid) valve– at the apex
– Tricuspid valve –inferior right corner
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
Conducting System
Figure 18.12Intrinsic Conduction System
Innervation• Heart rate is modified by extrinsic controls
• Nerves to the heart include:– Parasympathetic branches of the vagus nerve
– Sympathetic fibers – from sympathetic trunk ganglia
Figure 18.13
Cardiac Blood Supply
• Functional blood supply– Coronary arteries
• Arise from the aorta– Located in the coronary sulcus– Main branches
• Left and right coronary arteries
Blood Supply to the Heart
Figure 18.14
Disorders of the Heart• Coronary artery disease
– Atherosclerosis – fatty deposits– Angina pectoris – chest pain– Myocardial infarction – blocked coronary artery– Silent ischemia
• 3 to 4 million Americans have episodes of silent ischemia. People who have had previous heart attacks or those who have diabetes are especially at risk for developing silent ischemia.
• Heart muscle disease (cardiomyopathy) caused by silent ischemia is among the more common causes of heart failure in the United States.
~The American Heart Association
Disorders of the Heart• Heart failure
– Progressive weakening of the heart– Cannot meet the body’s demands for oxygenated blood
• Congestive heart failure – Heart can’t pump strongly enough causing
• Fluid accumulation (congestion) in lungs or body– Fluid accumulation in lungs = left sided heart failure– Fluid accumulation in body = right sided heart failure
• Cor pulmonale – Enlargement and potential failure of the right ventricle
• In response to pulmonary vasoconstricttion due to low oxygen levels without elevated CO2…
– Vasoconstriction re‐routes blood to areas of the lungs that are still capable of oxygenating blood effectively
Disorders of Conduction
• Ventricular fibrillation – Rapid, random firing of electrical impulses in the ventricles
• Atrial fibrillation – Multiple waves of impulses randomly signal the AV node
– Signals ventricles to contract quickly and irregularly
The Heart in Adulthood and Old Age
• Age‐related changes– Hardening and thickening of valve cusps– Decline in cardiac reserve
• Sympathetic control over heart is less efficient• Less severe in the physically active
– Fibrosis of cardiac muscle tissue • Lowers the amount of blood the heart can pump
Too Bad Desmond had never learned to recognize the early warning signs of a heart attack!