Microvascular circulation of the ascending colon in horses.

This research comprises an extensive study of the microvascular circulation of the ascending colon in healthy horses, utilizing microangiography, light microscopy and scanning electron microscopy for detailed observation and documentation.

Methodology

• The ascending colon, specifically the pelvic flexure with 30 centimeters of ventral and dorsal colon, was detached from 14 adult horses that were euthanized.
• The insides of these were cleaned with warm water and then submerged in a warm isotonic sodium chloride (NaCl) bath of 37-degrees Celsius.
• For eight of these horses, colic vessels, the primary blood vessels supplying the colon, were filled with a medium that could be visualized under X-ray (radio-opaque medium) to facilitate the microangiography process – a technique used to visualize blood vessels in detail.
• Post the angiography, samples were processed via standard histologic methods to enable observation under a light microscope.
• In the remaining six horses, vascular replicas were realized by injecting the vessels with two types of plastic substances, in order to be observed through a scanning electron microscope.

Results

• Arteries branched from the main colic vessels about every 2 centimeters towards the colonic tissue. This branching resulted in a network of interconnected blood vessels, known as an anastomotic plexus or colonic rete. However, each branch from the main vessel also continued into the colonic tissue.
• In addition, another set of vessels branched off from the colonic rete, supplying blood to the mesenteric lymph nodes, part of the immune system that helps fight infection.
• The arteries managed to penetrate deep into the tunica muscularis layer of the colon wall, moving into submucosa 3 to 4 centimeters towards the antimesenteric border where they formed another vascular network.
• From these submucosal arterioles, further branching occurred at right angles to provide blood flow to the mucosal capillaries, small blood vessels near the surface of the colon’s lining.
• These capillaries encircled the colonic glands and merged at the innermost layer of the colon, presenting a superficial luminal honeycomb-appearing vascular plexus – a network of blood vessels at the luminal surface with a honeycomb-like appearance.

Conclusion

• This research provides a comprehensive understanding and documentation of the microvascular structure of the ascending colon in horses, particularly at the pelvic flexure. The in-depth observation provided by different types of microscopy gives insightful information about how blood circulates in this part of the horse’s digestive system.