Serous Membrane
Illu stomach2.jpg
Stomach. (Serosa is labeled at far right, and is colored yellow.)
Details
Precursormesoderm
Identifiers
Latintunica serosa
MeSHD012704
FMA9581
Anatomical terminology
Serous membrane lines the pericardial cavity and reflects back to cover the heart—much the same way that an underinflated balloon would form two layers surrounding a fist.[1]
Serous membrane lines the pericardial cavity and reflects back to cover the heart—much the same way that an underinflated balloon would form two layers surrounding a fist.[1]

In anatomy, serous membrane (or serosa) is a smooth tissue membrane of mesothelium lining the contents and inner walls of body cavities, which secrete serous fluid to allow lubricated sliding movements between opposing surfaces. The serous membrane that covers internal organs is called a visceral membrane; while the one that covers the cavity wall is called the parietal membrane. Between the two opposing serosal surfaces is often a potential space, mostly empty except for the small amount of serous fluid.[2]

The Latin anatomical name is tunica serosa. Serous membranes line and enclose several body cavities, also known as serous cavities, where they secrete a lubricating fluid which reduces friction from movements. Serosa is entirely different from the adventitia, a connective tissue layer which binds together structures rather than reducing friction between them. The serous membrane covering the heart and lining the mediastinum is referred to as the pericardium, the serous membrane lining the thoracic cavity and surrounding the lungs is referred to as the pleura, and that lining the abdominopelvic cavity and the viscera is referred to as the peritoneum.

Structure

Serous membranes have two layers. The parietal layers of the membranes line the walls of the body cavity (pariet- refers to a cavity wall). The visceral layer of the membrane covers the organs (the viscera). Between the parietal and visceral layers is a very thin, fluid-filled serous space, or cavity.[3]

Visceral and parietal layers

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

For the heart, the layers of the serous membrane are called the parietal pericardium, and the visceral pericardium (sometimes called the epicardium). Other parts of the body may also have specific names for these structures. For example, the serosa of the uterus is called the perimetrium.

Schematic diagram of an organ invaginating into a serous cavity
Schematic diagram of an organ invaginating into a serous cavity

The pericardial cavity (surrounding the heart), pleural cavity (surrounding the lungs) and peritoneal cavity (surrounding most organs of the abdomen) are the three serous cavities within the human body. While serous membranes have a lubricative role to play in all three cavities, in the pleural cavity it has a greater role to play in the function of breathing.

The serous cavities are formed from the intraembryonic coelom and are basically an empty space within the body surrounded by serous membrane. Early in embryonic life visceral organs develop adjacent to a cavity and invaginate into the bag-like coelom. Therefore, each organ becomes surrounded by serous membrane - they do not lie within the serous cavity. The layer in contact with the organ is known as the visceral layer, while the parietal layer is in contact with the body wall.

Examples

In the human body, there are three serous cavities with associated serous membranes:

The two layers of serous membranes are named parietal and visceral. Between the two layers is a thin fluid filled space.[3] The fluid is produced by the serous membranes and stays between the two layers to reduce friction between the walls of the cavities and the internal organs when they move with respect to one another, such as when the lungs inflate or the heart beats. Such movement could otherwise lead to inflammation of the organs.[3]

Development

All serous membranes found in the human body formed ultimately from the mesoderm of the trilaminar embryo. The trilaminar embryo consists of three relatively flat layers of ectoderm, endoderm (also known as "entoderm") 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.

The lateral plate mesoderm later splits in half to form two layers bounding a cavity known as the intraembryonic coelom. Individually, each layer is known as splanchnopleure and somatopleure.

The intraembryonic coelom can now be seen as a cavity within the body which is covered with serous membrane derived from the splanchnopleure. This cavity is divided and demarcated by the folding and development of the embryo, ultimately forming the serous cavities which house many different organs within the thorax and abdomen.

Diseases

Mesotheliomas are neoplasias that are relatively specific for serous membranes. The modified Mullerian-derived serous membranes that surrounds the ovaries in females can give rise to serous tumors, a solid to papillary tumor type that may also arise within the uterus.

Anatomical images

See also

References

This Wikipedia entry incorporates text from the freely licensed Connexions [1] edition of Anatomy & Physiology [2] text-book by OpenStax College

  1. ^ J. Gordon Betts, Kelly A. Young, James A. Wise, Eddie Johnson, Brandon Poe, Dean H. Kruse, Oksana Korol, Jody E. Johnson, Mark Womble, Peter DeSaix (Apr 25, 2013). "1.6 Anatomical Terminology". Anatomy and Physiology. Houston, Texas: OpenStax.((cite book)): CS1 maint: uses authors parameter (link)
  2. ^ "The Anatomy of Lining and Covering Tissues-Membranes!". McGraw-Hill Companies. Retrieved September 2, 2017.
  3. ^ a b c d "Anatomy & Physiology". Openstax college at Connexions. Retrieved November 16, 2013.