What is the Adventitia?

Adventitia is a type of connective tissue found on the outermost layer of some organs and structures in the body. Others may be covered with serosa, a membrane that produces serous fluids for lubrication. This type of tissue is found through the body, everywhere from the external lining of abdominal organs to the outer layer of blood vessels. One of the most notorious examples of a disorder involving the adventitia is scurvy, a disease that causes a breakdown of connective tissue and a cascading series of accompanying medical problems.

This tissue is primarily comprised of collagen, a very strong and highly flexible material. The adventitia, also known as the tunica adventitia, is designed to provide structure and support the organs. It keeps organs in place, as well as binding different physical structures together, and creates a clear framework for underlying tissues, allowing organs to keep their shape. This preserves organ function.

In addition, the adventitia provides a layer of defense for the underlying structure. If infectious materials get loose inside the body, they will need to pass through this layer of tissue before they can penetrate structures like the organs and blood vessels. The added barrier can prevent the spread of infection in some cases. It also acts as a shock absorber when the body sustains trauma such as a blow or puncture wound. This can be very useful for protecting organs from serious damage.

Sometimes, connective tissue thickens in response to disease or injury. In the adventitia, this can create increased rigidity and stiffness, potentially causing a problem. The thickening can also be evidence of a history of inflammation or injury, even if no problems were noticed at the time the damage was incurred. The history of disease in the body can sometimes be traced by looking for tell-tale tissue changes associated with tissue damage, even after the infection or initial injury is long gone.

Thinning of the connective tissue, as seen in scurvy and some connective tissue disorders, can be catastrophic for the patient. As the adventitia pulls apart, the underlying structure can collapse, releasing its contents. In scurvy, this can be seen in the case of freely bleeding gums leading to loose teeth because the gums are no longer providing structural support. Patients with connective tissue disorders can also develop organ failure as the protective outer walls of their organs break down and they are no longer able to function.