The omentum is a sheet of fatty tissue within the abdominal cavity of mammals, including mice. While it appears to be a simple membrane, it is a complex organ that performs a range of functions related to immunity, metabolism, and tissue repair.
Anatomical Structure and Cellular Makeup
In mice, the greater omentum is a thin band of adipose tissue that extends from the spleen and pancreas, draping over the abdominal organs. This is not a passive layer of fat but a dynamic tissue with a rich blood supply and a diverse cellular population. Its position allows it to move with the gut, providing a mobile barrier.
The omentum is composed of fat cells (adipocytes), fibroblasts, and a network of blood and lymphatic vessels. It is also populated by immune cells like macrophages, lymphocytes, and dendritic cells. These cells are often organized into specialized clusters, preparing the omentum for its immunological roles.
The Omentum as an Immune Organ
The omentum acts as a sentinel for the abdominal cavity, detecting and responding to threats. It monitors the peritoneal fluid, collecting foreign particles, pathogens, and cellular debris. This surveillance is performed by specialized structures known as “milky spots,” which are dense aggregates of immune cells.
Named for their whitish appearance, milky spots function as filters, sampling the contents of the abdominal cavity. They are rich in macrophages and lymphocytes that trap antigens and initiate an immune response. When an infection is detected, these clusters increase in size and number to coordinate the body’s defenses.
Metabolic and Regenerative Capabilities
Beyond its immune functions, the omentum is an active metabolic organ. As a visceral fat depot, its adipocytes release hormones and signaling molecules that influence the body’s overall metabolism. These molecules can affect nearby organs, such as the liver, and contribute to systemic metabolic regulation.
The omentum also possesses a capacity for tissue repair and regeneration. This ability is attributed to mesenchymal stem cells found within its structure. These stem cells can differentiate into various cell types. When an injury occurs, the omentum can migrate to the site and these stem cells facilitate healing.
Role in Disease and Research
The mouse omentum is a focus in disease research, particularly for its role in cancer progression. It is a frequent site for the metastasis, or spread, of certain cancers, most notably ovarian cancer. Cancer cells are attracted to the omentum’s fatty environment, which provides them with lipids as a fuel source to support their growth.
The omentum’s involvement in metabolic diseases is also studied. In conditions like obesity, the omental fat can become inflamed, releasing inflammatory molecules that contribute to insulin resistance and type 2 diabetes. Because the mouse omentum shares many features with that of humans, it serves as a model for studying these processes and developing new therapies.