Histology%20for%20Pathology%20Cardiac%20System

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Histology for PathologyCardiac System

• Theresa Kristopaitis, MD
• Associate Professor
• Director of Mechanisms of Human Disease
• Kelli A. Hutchens, MD, FCAP
• Assistant Professor
• Assistant Director of Mechanisms of Human Disease
• Loyola Stritch School of Medicine

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Objectives

• 1. Identify the 3 layers of the heart
  endocardium, myocardium, epicardium
• 2. Differentiate cardiac, skeletal and smooth
  muscle on HE stained slides citing the key
  distinguishing morphologic features
• 3. Define intercalated disc
• 4. Name the layer of the heart in which Purkinje
  fibers are found and describe their function
• 5. Explain which chamber of the heart has the
  thickest layer of myocardium vs the thinnest
• 6. Explain the general histologic structure of a
  cardiac valve

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Heart Wall
Myocardium
Endocardium
Epicardium
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Endocardium

• Innermost layer
• Composed of
• Simple squamous epithelium (endothelium)
• Connective Tissue
• Subendocardium in contact with cardiac muscle
  and contains small vessels, nerves, and Purkinje
  Fibers.

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Purkinje Fibers

• Impulse conducting fibers
• Large modified muscle cells
• Cluster in groups together
• 1-2 nuclei and stain pale due to fewer myofibrils
• Terminal branches of the AV bundle branches
  located in the subendocardial connective tissue

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Myocardium

• Thickest layer of the heart
• Thickest in left ventricle because must pump hard
  to overcome high pressure of systemic circulation
• Right atrium the thinnest because of low
  resistance to back flow
• Consist of cardiac muscle cells myocytes
• Different from smooth or skeletal muscle cells
  due to placement of nuclei, cross striations, and
  intercalated disks
• Intercalated disks
• Junctional complexes that contain fascia
  adherens, desmosomes, and gap junction to provide
  connection and communication.
• Bind myocytes and allow ion exchange to
  facilitate electrical impulses to pass

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Cardiac Myocytes
Branching myocytes
Central nuclei Fibers with Cross Striations
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Smooth Muscle Long, slender central nuclei,
lying within narrow, fusiform cells. No cross
striations
Skeletal muscle Fibers with cross-striations and
peripheral nuclei.
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Epicardium

• Outermost layer of the heart
• Composed of connective tissue with nerves,
  vessels, adipocytes and an outer layer of
  mesothelium
• Mesothelium secretes pericardial fluid
• Covers and protects the heart

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Cardiac Valves

• 4 valves
• 2 AV (mitral and tricuspid) in the chambers
• 2 semilunar (aortic /pulmonary)
• Composed of connective tissue layers covered by
  endothelium on each side 3 layers
• Spongiosa loose collagen
• Fibrosa dense core of connective tissue
• Ventricularis dense connective tissue with many
  elastic and collagen fibers