Scanning electron and light microscopy of the mucosa of the equine ileocaecal junction.

The research examines the mucosal surface of the ileocaecal junction in five horses and one donkey using scanning electron microscopy and light microscopy, establishing four distinct regions based on differences in surface morphology.

Methodology

• The researchers used scanning electron microscopy and light microscopy, two techniques that provide detailed and high-resolution images, to examine the ileocaecal junction mucosal surface of five horses and one donkey.

Morphological Differences

• Based on the differences in surface morphology observed under the microscope, the ileocaecal junction was divided into four distinct regions.

Distinct regions and their characteristics

• The distal or furthest end of the ileum, the last part of the small intestine, was differentiated by the presence of typical finger-like villi, or small hair-like structures.
• The second region presented short, stubby villi and it gradually merged into a third region that represents the actual transitional zone between the small and large intestines.
• In the third region, the small projections or villi fused together, forming low ridges arranged in circular, semi-circular, or S-shaped patterns. The fused villi had indentations at the tips, making them appear doughnut-like.
• The last region, referred to as the caecal part of the ileocaecal junction, formed the fourth region. This was distinctly characterized by the absence of villi and the presence of regularly spaced crypt openings, each of which were surrounded by a slightly raised circular mound.

Significance

• This study provides new insights into the surface morphology of the equine ileocaecal junction, which could improve our understanding of how nutrients are absorbed and diseases are contracted. The morphology distinctions in these four regions might be related to different functional characteristics.