muscles of the heart

• how many layers does the wall of the heart consist of?

  3
• what are the 3 layers layers pf the wall of the heart?

  endocardium , myocardium and epicardium
• what are the layers of the endocardium?

  endothelium: simple squamous epithelium

  subendothelial connective tissue: continuous with that of blood vessels entering and exiting the heart

  subendocardium: layer of connective tissue where branching of the impulse-conducting system are located
• what is the subendothelial CT?

  subendothelial connective tissue: continuous with that of blood vessels entering and exiting the heart
• what is subendocardium?


  layer of CT where branches of the impulse conducting system are located
• myocardium features and components

  thickest coat

  composed of cardiac muscle fibers bound together by connective tissue
• what is the visceral layer of pericardium?

  epicardium
• epicardium components 


  it is the visceral layer of pericardium

  consists of simple squamous mesothelium supported by loose connective tissue containing coronary vessels, nerves and adipose tissue
• cardiac muscle


  striated and involuntary
• control of cardiac muscle

  contraction is initiated by the spontaneous depolarization of pace maker cells
• structure of CT of cardiac muscle by LM:
• structure of CT of cardiac muscle by LM:

  perimysium: highly vascularized formed of collagen and elastic fibers which are present between the bundles of cardiac muscle fibers

  endomysium: a network of reticular fibers surrounds each muscle fiber
• perimysium


  highly vascularized formed of collagen and elastic fibers which are present between the bundles of cardiac muscle fibers
• endomysium


  a network of reticular fibers surrounds each muscle fiber
• structure of cardiac muscle fibers by LM

  1 they are long cylindrical fibers which branch and anastomose leaving slit like spaces between them. thus in different cuts muscle fibers could be longitudinal transverse and oblique

  2 the fibers show fainter striations than SKM fibers

  3 each CMF consists of short columnar cells called cardiomyocytes joined by intercalated discs that run transversely across the fiber

  4 each cardiomyocyte has a single central oval nucleus
• why do the cardiac muscle fibers show fainter striations?

  as the myofibrils branch and anastomose thus they are not perfectly in register with one another