The Microscopic Structure of the Omentum in Healthy Dogs: The Mystery Unravelled

Abstract

The canine omentum has many valuable properties but is still an underestimated organ. It contributes in many ways to the protection of the peritoneal cavity through its versatility on immunological level, but also through its role during angiogenesis, absorption, adhesion and fat storage. Despite a wide range of applications, the basic structure of the omentum is not well documented. This study provides an insight in the microscopic structure of the canine omentum through both light microscopic and electron microscopic investigations. Two regions could be distinguished in the canine omentum: translucent and adipose-rich regions. The translucent regions were composed of two different layers: a continuous flattened mesothelium on top of a submesothelial connective tissue matrix. The adipose-rich regions consisted of a substantial layer of adipocytes on which a flattened continuous mesothelium was present. Between those two layers, a few strands of collagen fibres could be detected. Large aggregates of immune cells, the so-called milky spots, were not observed in the omentum of healthy dogs. Only a limited number of leucocytes, macrophages and neutrophils were found, scattered throughout the connective tissue in the translucent regions. At the level of the adipose-rich regions, the immunological population was virtually non-existent.

Valuation of angiogenesis in bovine xenografts implanted in intracorporal sites of rabbits as models of in-vivo bioreactors

“…Histological analysis confirmed the presence of neovascularization at all times and sites of analysis, as it is widely reported in the literature (Simion et al, 2007;Araújo et al, 2009;Athanasiou et al, 2009;Mardas et al, 2010). Neovascularization was present in both peri and intra-implant tissues; and was more evident in subgroup A1 (omentum bag) due to the intense immunological, angiogenic, absorptive, adhesive, and adipocyte storage capacity of the organ (Huyghe et al, 2016). The angiogenic capacity of the omentum is given by the presence of the (VEGF), one of the main precursors of the development of vessels in the body (Zhang et al, 1997).…”

Fat-Associated Lymphoid Clusters in Inflammation and Immunity

“…Moreover, the omentum contains two distinguishable regions: a translucent collagenous membrane-like region and an adipose-rich region containing blood and lymphatic vessels, stromal cells, and clusters of immune cells (43). In mice and humans, MS have been found in the adipose region of the omentum, whereas in dogs, the aggregates of lymphoid cells are only found scattered in the translucent area (43, 44). However, no clear distinction in the exact location of MS within the omentum has been established.…”

The Omentum—A Forgotten Structure in Veterinary Surgery in Small Animals’ Surgery

“…Many publications rely on data from humans, laboratory animals, or structures like the pleura or peritoneum [10]. In 2016, a thorough analysis of the tissue composition in the omentum of clinically healthy dogs was carried out [11]. This structure was identified at the macroscopic level in two different zones: the translucent and adipose-rich regions, just like in other mammals [12][13][14].…”