MH 073-074 Heart

Aortic Valve & Cardiac Skeleton
(H&E)

The specimen shows the anatomical relationship between the left ventricle and the aorta, with the aortic valve positioned between these structures.

• Left Ventricle (on the right side):
  • Receives oxygenated blood from the left atrium and pumps it into the systemic circulation via the aorta
  • Heart chamber with the thickest myocardium
    • Requires much higher pressure than the pulmonary circulation
• Aorta (on the left side):
  • As the largest artery in the body, the aorta receives blood from the left ventricle
  • Primary conduit for the distribution of oxygenated blood to the major arteries
• Aortic Value:
  • Consists of three leaflets (only one visible) that open and close during ventricular contraction

Aortic Valve & Cardiac Skeleton
(H&E)

Hematoxylin and eosin (H&E) staining is the primary method for routine histological examination.

Aortic Valve

The aortic valve is located between the left ventricle and the aorta. It typically consists of three leaflets (or cusps) that open and close during ventricular contraction. This section passes through one of the leaflets:

• Endothelium:
  • Simple squamous epithelium that covers both sides of the leaflet
  • Continuous with the lining of the heart chambers
• Dense Connective Tissue:
  • Forms the central core composed of collagen and elastic fibers
  • Continuous with the fibrous skeleton of the heart
• Avascular Structure:
  • Nutrients and oxygen diffuse from the blood in the heart chambers

Unlike the atrioventricular valves (tricuspid and mitral valves), the aortic valve operates without chordae tendineae or papillary muscles, relying instead on pressure differences for proper function.

Cardiac Skeleton

The cardiac skeleton is dense, fibrous connective tissue that forms the structural framework of the heart.

• Fibrous Rings: Four rings of dense irregular connective tissue around the heart valves
  • Densely packed collagen fibers (dark red bands) are clearly distinguishable from the adjacent cardiac muscle (pink/red)
  • Anchoring points for the valve leaflets and insertion points for the myocardium of the heart chambers
• Electrical Insulation: It electrically insulates the atria above the fibrous rings from the ventricles below

Aortic Valve & Cardiac Skeleton
(Phosphotungstic Acid/Hematoxylin)

Phosphotungstic acid/hematoxylin (PTAH) staining shows better contrast between muscle fibers (dark purple/gray) and connective tissue (pink/red), muscle striations, and intercalated discs compared to routine H&E staining. This makes it especially useful for examining cardiac architecture.

• Left Ventricle (on the right side):
  • Myocardium: Cardiac muscle cells exhibit dark purple/gray staining, clearly delineating individual muscle fibers with striations
  • Intercalated Discs: Appear as dark lines between adjacent cardiac muscle cells in longitudinal sections
  • Coronary Vessels: Blood vessel walls (muscular artery and arteriole) within the myocardium exhibit pink/red staining of their connective tissue components
• Aortic Valve:
  • Endothelium: Stained light pink
  • Dense Connective Tissue: Stained darker pink/red
• Cardiac Skeleton:
  • Fibrous Rings: Densely packed collagen fibers stain intensely pink/red, providing excellent contrast against the adjacent cardiac muscle

Technical Note: The alternating dark and light bands observed within the left ventricular myocardium and the tunica media of the aorta represent sectioning artifacts rather than histological features.