Morphological study of the sinus node and its artery in yak

Area of Science:

• Veterinary Anatomy
• Cardiac Electrophysiology

Background:

• The cardiac conduction system's structure and function are crucial for understanding heart rhythm.
• Detailed histological and ultrastructural studies of the sinus node in various species contribute to comparative cardiology.

Purpose of the Study:

• To investigate the histological and ultrastructural characteristics of the yak (Bos grunniens) sinus node.
• To analyze the morphology and vascular supply of the yak sinus node artery.

Main Methods:

• Histological examination of sinus node tissue.
• Transmission electron microscopy (TEM) for ultrastructural analysis.
• Injection-corrosion casting, angiography, and histology for vascular studies.

Main Results:

• The yak sinus node contains a collagen framework and two main cell types: pacemaker (P) cells and transitional (T) cells, differing in mitochondrial size and myofibril content.
• P cells exhibit a perinuclear clear zone, while T cells are longer, slender, and varied in shape.
• Nerve fibers and ganglions are present at the sinus node periphery. Gap junctions were detected centrally via TEM, despite negative anti-connexin43 staining.
• The sinus node artery predominantly originates from the left coronary artery (98%) and runs along the sinus node periphery, featuring an internal elastic membrane and associated nerve bundles.

Conclusions:

• The yak sinus node possesses distinct cellular components and a specific vascular architecture.
• The findings provide valuable insights into the comparative anatomy and physiology of the cardiac conduction system in yaks.