Ch 19 Heart

• Cardiovascular system


  Heart and blood vessels

  
• Circulatory system


  Heart, blood vessels, and the blood

  
• Major divisions of circulatory system

  • Pulmonary circuit: right side of heart
  • Systemic circuit: left side of heart

  
• Pulmonary circuit


  • Carries blood to lungs for gas exchange and back to heart
• Systemic circuit


  • Supplies oxygenated blood to all tissues of the body and returns it to the heart

  
• Blood flow through the heart

  1. Ventricles relax

  2. Ventricles contract

  
• Left side of heart

  • Fully oxygenated blood arrives from lungs via pulmonary veins
  • Blood sent to all organs of the body via aorta

  
• Right side of heart

  • Oxygen-poor blood arrives from inferior and superior venae cavae
  • Blood sent to lungs via pulmonary trunk

  
• Heart located in mediastinum, between lungs

  
• Heart


  • Base—wide, superior portion of heart, large vessels attach here
  • Apex—tapered inferior end, tilts to the left
  • In adult: weighs 10 ounces, 3.5 in. wide at base, 5 in. from base to apex
  • At any age, heart is size of fist

  
• Pericardium—double-walled sac that encloses the heart

  
• Pericardium


  • Allows heart to beat without friction, provides room to expand, yet resists excessive expansion
  • Anchored to diaphragm inferiorly and sternum anteriorly
• Fibrous pericardium


  Outer wall, not attached to heart
• Serous pericardium


  • Parietal layer—lines fibrous pericardium
  • Visceral layer (epicardium)—covering heart surface

  
• Pericardial cavity


  Space between parietal and visceral layers of serous pericardium, filled with 5 to 30 mL of pericardial fluid
• Pericarditis


  Painful inflammation of the membranes
• Heart wall has three layers: epicardium, myocardium, and endocardium

  
• Epicardium


  • Serous membrane covering heart
  • Adipose in thick layer in some places
  • Coronary blood vessels travel through this layer

  
• Endocardium


  • Smooth inner lining of heart and blood vessels
  • Covers the valve surfaces and is continuous with endothelium of blood vessels

  
• Myocardium


  • Layer of cardiac muscle proportional to workload
  • Muscle spirals around heart which produces wringing motion, vortex of the heart
  • Fibrous skeleton of the heart: framework of collagenous and elastic fibers
  • Provides structural support and attachment for cardiac muscle and anchor for valve tissue
  • Electrical insulation between atria and ventricles; important in timing and coordination of contractile activity

  
• Four chambers: right and left atria, right and left ventricles
• Coronary sulcus


  Separates atria and ventricles
• Interventricular sulcus


  Overlies the interventricular septum that divides the right ventricle from the left
• Sulci contain coronary arteries
• Interatrial septum


  Wall that separates atria
• Pectinate muscles


  Internal ridges of myocardium in right atrium and both auricles

  
• Interventricular septum


  Muscular wall that separates ventricles
• Trabeculae carneae


  Internal ridges in both ventricles; may prevent ventricle walls from sticking together after contraction
• Atrioventricular (AV) valves


  • Control blood flow between atria and ventricles
  • Right AV valve has three cusps (tricuspid valve)
  • Left AV valve has two cusps (mitral valve, formerly 'bicuspid')
  • Chordae tendineae: cords connect AV valves to papillary muscles on floor of ventricles

  
• Semilunar valves


  • Control flow into great arteries; open and close because of blood flow and pressure
  • Pulmonary semilunar valve: in opening between right ventricle and pulmonary trunk
  • Aortic semilunar valve: in opening between left ventricle and aorta

  
• Blood flow through the chambers

  1. Ventricles relax

  2. Ventricles contract
• 5% of blood pumped by heart is pumped to the heart itself through the coronary circulation to sustain its strenuous workload

  
• Left coronary artery (LCA)

  • Branches off the ascending aorta
  • Anterior interventricular branch (also know as the Left Anterior Descending or LAD)
  • Circumflex branch
• Right coronary artery (RCA)


  • Branches off the ascending aorta
  • Supplies right atrium and sinuatrial node (pacemaker)
  • Right marginal branch
  • Posterior interventricular branch

  
• Flow through coronary arteries is greatest when heart relaxes
• Angina pectoris


  Chest pain from partial obstruction of coronary blood flow
• Myocardial infarction (MI)


  Sudden death of a patch of myocardium resulting from long-term obstruction of coronary circulation
• Cardiomyocytes


  Striated, short, thick, branched cells, one central nucleus surrounded by light-staining mass of glycogen
• Repair of damage of cardiac muscle is almost entirely by fibrosis (scarring)
• Intercalated discs


  Join cardiomyocytes end to end with three features: interdigitating folds, mechanical junctions, and electrical junctions