Difference Between Adventitia and Serosa

Adventitia vs Serosa
 

Serosa is different from adventitia because serosa is for lubrication where as adventitia is to bind structures together.

What is Adventitia?

Adventitia is a connective tissue. It is the outermost connective tissue layer that surrounds any structure such as organs or vessels. Sometimes it is also referred to as the tunica externa especially when it is the adventitia of artery. Sometimes its function may be considered as complementary to serosa. In the abdomen, surrounding an organ with serosa or adventitia depends on whether the organ is peritoneal or retroperitoneal. Peritoneal organs are surrounded by serosa, and retroperitoneal organs are surrounded by adventitia. In certain organs, the muscularis externa is bound by adventitia. Those organs are the oral cavity, thoracic esophagus, ascending colon, descending colon and rectum. In the duodenum, the muscularis externa is bound by both adventitia and serosa.

What is Serosa?

Serosa is a smooth membrane. It consists of a layer of cells and a thin connective tissue layer. The cells secrete serous fluid. Serosa encloses certain body cavities. Those body cavities are known as the serous cavities. In serous cavities, serosa secretes a lubricating fluid to reduce the friction due to muscle movement. Serosa comprises two layers. Upper layer consists of secretory epithelial cells, and the lower layer consists of connective tissue. The epithelial layer is a simple squamous layer. It contains a layer of flat nucleated cells, which are capable of secreting serous fluid. The squamous layer is bound to the connective tissue layer below. Blood vessels and nerve supply is found in the connective tissue layer. Serosa of different organs are known by different names. In the uterus, serosa is known as the perimetrium and, in the heart, the serosa includes the pericardium and the epicardium. There are three serous cavities in the body of the humans. Those are the pericardial cavity surrounding the heart, pleural cavity surrounding the lungs and the peritoneal cavity surrounding the most organs in the abdomen. The overall function of the serosa is lubrication. In addition, it has an important role in breathing in the lungs. Intraembryonic coelom gives rise to the serous cavities. Those are empty spaces surrounded by serosa. Serosa has a mesodermal origin. During embryonic development, mesoderm is segmented into paraxial mesoderm, intermediate mesoderm, and lateral plate mesoderm. Lateral plate coelom splits forming the intraembryonic coelom.

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