What is a Serous Membrane?

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In Anatomy, a serous membrane or ‘Serosa’ is a smooth membrane consisting of a thin layer of cells which secrete serous fluid. Serous membranes line and enclose several body cavities, known as serous cavities, where they secrete a lubricating fluid which reduces friction from muscle movement. Serosa should not be confused with adventitia, a connective tissue which binds together structures rather than reducing friction between them. In the body, membrane has more than one meaning. A membrane can be lipid bilayer that surrounds a cell- a cell membrane – or it can be a thin layer of tissue made up of many different cells. The cell membrane controls what enters and leaves the You do not have access to view this node, but at the tissue layer, a membrane forms a barrier. A serous membrane belongs to this second type of membrane. Serous membrane is also known as ‘serous tunic’.


What is the Structure of Serous membrane?

Each Serous membrane is composed of secretory epithelial layer and a connective tissue layer underneath.

  • Epithelial layer: The Epithelial layer, known as ‘mesothelium’, consists of a single layer of avascular flat nucleated cells which produce the lubricating serous fluid. This fluid has a consistency similar to mucus. These cells are bound tightly to the underlying connective You do not have access to view this node.
  • Connective tissue layer: The connective tissue layer provides the blood vessels and nerves for the overlying secretory You do not have access to view this node, and also serves as the binding layer which allows the whole serous membrane to stick to organs and other structures.


What are the serous cavities within the human body?

The Serous cavities are formed from the intraembryonic coelom / cavity, and are basically an empty space within the body surrounded by serous membrane. Early in embryonic life, internal body organs develop nearby to a cavity and get enveloped in a bag type structure. Consequently, each organ becomes surrounded by the serous membrane. They do not lie within the serous cavity. There are three serous cavities within the You do not have access to view this node. They are as follows.

  • The Pericardial cavity which is surrounding the heart which includes the outer parietal pericardium and the inner visceral pericardium.
  • The Pleural cavity which is surrounding the lungs.
  • The Peritoneal cavity which is surrounding most organs of the You do not have access to view this node.

Other parts of the body may also have specific names for theses structures. For instance, the Serosa of the uterus is called Perimetrium. Even though, serous membranes have a lubricative role to play in all the three cavities, in the pleural cavity it has a major role to play in the function of breathing.


What is the Embryological origin of serous membrane?

All serous membranes found in the human body formed ultimately from the mesoderm layer of the embryo. The embryo consists of three flat layers of ectoderm, endoderm and mesoderm. As the embryo develops, the mesoderm starts to segment into three main regions, the paraxial mesoderm, the intermediate mesoderm and the lateral plate mesoderm.   

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