MH 070 Heart

Cardiac Ventricles

The cardiac ventricles are the two lower chambers of the heart, acting as high-pressure pumps that propel blood through the pulmonary and systemic circulation.

• Right Ventricle: Receives deoxygenated blood from the right atrium and pumps it through the pulmonary circulation to the lungs
• Left Ventricle: Receives oxygenated blood from the left atrium and forces it through the systemic circulation to supply the entire body

Their significantly thicker muscular walls compared to the atria reflect their role as forceful ejection chambers rather than simple reservoirs, distinguishing them structurally from the thinner-walled atrial chambers.

The left ventricle demonstrates the greatest wall thickness due to the higher pressures required for systemic circulation compared to the lower-pressure pulmonary circuit.

Right Ventricle

The right ventricle serves as the primary pumping chamber for the pulmonary circulation, propelling deoxygenated blood through the pulmonary arteries to the lungs for oxygenation. Its internal architecture features prominent muscular ridges and papillary muscles that anchor the tricuspid valve, ensuring unidirectional blood flow during the cardiac cycle.

The right ventricular wall demonstrates the classic three-layered cardiac architecture:

• Endocardium (Inner Layer)
  • Endothelium: Simple squamous epithelium lines the inner surface of the heart
    • Flattened nuclei visible in some regions
  • Subendothelial Layer: Thin layer of connective tissue of collage and elastic fibers that supports the endothelium
• Myocardium (Middle Layer)
  • Cardiomyocytes: Thickest layer responsible for the chamber's pumping action
  • Other Components: Blood vessels (muscular artery, arteriole, capillaries), nerve fibers, and scattered adipocytes
• Epicardium (External Layer)
  • Mesothelium: Simple squamous epithelium that covers the outer surface of the heart
    • Damaged or missing in this specimen
  • Subepicardial Layer: Dense irregular connective tissue with variable amounts of adipose tissue
  • Relationship to Pericardium: Forms the visceral layer of the pericardium that surrounds the heart

Left Ventricle

The left ventricle functions as the heart's most powerful pumping chamber, generating the high pressures necessary to propel oxygenated blood throughout the systemic circulation. Its thick-walled architecture and conical shape optimize the expulsion of blood. Like the right ventricle, it contains papillary muscles that anchor the mitral/bicuspid valve.

The left atrial wall demonstrates the classic three-layered cardiac architecture:

• Endocardium (Inner Layer):
  • Endothelium: Simple squamous epithelium lines the inner surface of the heart
    • Damaged or missing in this specimen
  • Subendothelial Layer: Thin layer of connective tissue of collage and elastic fibers that supports the endothelium
• Myocardium (Middle Layer)
  • Cardiomyocytes: Thickest cardiac muscle layer among all four heart chambers
  • Arrangement: Bundles of muscle fibers are arranged in complex spiral patterns to optimize ejection efficiency
  • Other Components: Blood vessels, nerve fibers, and scattered adipocytes
• Epicardium (External Layer)
  • Mesothelium: Simple squamous epithelium that covers the outer surface of the heart
  • Subepicardial Layer: Dense irregular connective tissue with a prominent layer of loose adipose connective tissue
  • Relationship to Pericardium: Forms the visceral layer of the pericardium that surrounds the heart