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• Size and Location OH-Position of the Heart and Associated Blood Vessels and SideB:13954

• Nine (9) inches long x three (3) inches wide.
  • Located within the mediastinum, bordered laterally by the lungs, posteriorly by the backbone, and anteriorly by the sternum.
• Base--attached to several large blood vessels and lies beneath the second rib.
• Apex--at the fifth intercostal space

B. Coverings of the Heart OH-Pericardium and Heart Wall

• The heart and the proximal ends of the large blood vessels are enclosed by the pericardium. 13955
  • Consists of an outer fibrous bag--fibrous pericardium which surrounds a more delicate double-layered sac.

• Inner layer of this sac--visceral pericardium (epicardium) covers the heart.

• At the base of the heart the visceral pericardium turns back on itself to become the parietal pericardium.
• Between the parietal and visceral layers is the pericardial cavity which contains serous fluid--pericardial fluid.
  • The fluid reduces friction between the pericardial membranes when the heart moves within them.

• C. Wall of the Heart OH-Pericardium and Heart Wall 13961

• Made up of three (3) distinct layers:
  • Outer epicardium
  • Middle pericardium
  • Inner endocardium

• Epicardium
  • Corresponds to the visceral pericardium.
  • Functions as an outer protective layer.
  • Serous membrane that consists of connective tissue covered by epithelium.
  • Includes blood capillaries, lymph capillaries, and nerve fibers.
• Myocardium
  • Relatively thick.
  • Consists largely of cardiac muscle tissue responsible for forcing blood out of the heart chambers.
  • Muscle fibers are arranged in planes, separated by connective tissues that are richly supplied with blood capillaries, and nerve fibers.
• Endocardium
  • Consists of epithelial and connective tissue that contains many elastic and collagenous fibers.
  • Connective tissue also contains blood vessels and some specialized cardiacmuscle fibers called Purkinje fibers.
  • Lines all of the heart chambers and covers heart valves.
  • Is continuous with the inner lining of blood vessels--endothelium.

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