1. PowerPoint ® Lecture Slides prepared by Leslie Hendon, University of Alabama, Birmingham HUMAN ANATOMY fifth edition MARIEB | MALLATT | WILHELM 18 Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings The Heart PART 2

2. Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings Heart Valves – Valve Structure  Each valve composed of  Endocardium with connective tissue core  Atrioventricular (AV) valves  Between atria and ventricles  Aortic and pulmonary valves  At junction of ventricles and great arteries

3. Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings Fibrous Skeleton  Surrounds all four valves  Composed of dense connective tissue  Functions  Anchors valve cusps  Prevents overdilation of valve openings  Main point of insertion for cardiac muscle  Blocks direct spread of electrical impulses

4. Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings Heart Valves – Valve Structure Figure 18.8a

5. Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings Function of the Atrioventricular Valves Figure 18.9a

6. Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings Function of the Atrioventricular Valves Figure 18.9b

7. Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings Function of the Semilunar Valves Figure 18.10a, b

8. Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings Heart Sounds  “Lub-dup” – sound of valves closing  First sound “lub”  The AV valves closing  Second sound “dup”  The semilunar valves closing

9. Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings Heart Sounds Figure 18.8a

10. Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings 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

11. Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings Heart Sounds Figure 18.11

12. Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings Cardiac Muscle Tissue  Forms a thick layer called myocardium  Striated like skeletal muscle  Contractions pump blood through the heart and into blood vessels  Contracts by sliding filament mechanism

13. Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings Cardiac Muscle Tissue  Cardiac muscle cells  Short  Branching  Have one or two nuclei  Not fused colonies like skeletal muscle

14. Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings Cardiac Muscle Tissue  Cells join at intercalated discs  Complex junctions  Form cellular networks  Cells are separated by delicate endomysium  Binds adjacent cardiac fibers  Contains blood vessels and nerves

15. Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings Cardiac Muscle Tissue  Intercalated discs – complex junctions  Adjacent sarcolemmas interlock  Possess three types of cell junctions  Desmosomes  Fasciae adherans – long desmosome-like junctions  Gap junctions

16. Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings Microscopic Anatomy of Cardiac Muscle Figure 18.12a, b

17. Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings Cardiac Muscle Tissue Figure 18.12c, d

18. Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings Cardiac Muscle Tissue  Triggered to contract by Ca 2+ entering the sarcoplasm  Signals sarcoplasmic reticulum to release Ca 2+ ions  Ions diffuse into sarcomeres  Trigger sliding filament mechanism

19. Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings Cardiac Muscle Tissue  Not all cardiac cells are innervated  Will contract in rhythmic manner without innervation  Inherent rhythmicity  Is the basis for rhythmic heartbeat

20. Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings 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

21. Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings Conducting System Figure 18.14

22. Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings Innervation  Heart rate is altered by external controls  Nerves to the heart include  Visceral sensory fibers  Parasympathetic branches of the vagus nerve  Sympathetic fibers – from cervical and upper thoracic chain ganglia Figure 18.15