Cardiovascular System Part 2: The Heart The Heart what it is A - PowerPoint PPT Presentation

Cardiovascular System Part 2: The 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 lateral to 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 Left Atrium Right Atrium Left Ventricle Right Ventricle

Pathway of Blood Through the Heart • Begin oxygen ‐ poor blood in the superior and inferior venae cavae and the coronary sinus Right Right Pulmonary Pulmonary Right Trunk Atrium Ventricle Valve* Atrioventricular Valve* Pulmonary Pulmonary Lungs Veins Arteries Left Left Aortic Left Atrium Aorta Ventricle Atrioventricular Valve* Valve* Systemic & Cardiac Circulation *Alternate Names exist for these valves!

Heart Chambers Left Atrium Right Atrium Left Ventricle Right 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 Isovolumetric Ventricular Contraction Figure 18.9b

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 18.12 Intrinsic 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

Congenital Heart Defects Figure 18.17a, b

Congenital Heart Defects Figure 18.17c, d

Congenital Heart Defects Figure 18.17e, f

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!