Serous membrane

Serous Membrane
Stomach. (Serosa is labeled at far right, and is colored yellow.)
Details
Precursor	mesoderm
Identifiers
Latin	tunica serosa
MeSH	A10.615.789
FMA	9581
*Anatomical terminology* [edit on Wikidata]

Gastrointestinal wall

This article is one of a series on the
General structure Epithelium Mucosa Submucosa Circular muscle Longitudinal muscle Serosa Adventitia
Specific Meissner's plexus Auerbach's plexus
Organs Esophagus Stomach Intestines

In anatomy, serous membrane (or serosa) is a smooth tissue membrane consisting of two layers of mesothelium, which secrete serous fluid. The inner layer that covers organs (viscera) in body cavities is called the visceral membrane; this inner layer of epithelial cells is followed by a connective tissue; after the connective tissue is the second layer of epithelial cells of the serous membrane called the parietal layer.^[1]

The Latin anatomical name is tunica serosa. 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 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

A serous membrane (also referred to as a serosa) is one of the thin membranes that cover the walls and organs in the thoracic and abdominopelvic cavities. 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.^[2]

Visceral and parietal layers

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

The epithelial layer, known as mesothelium, consists of a single layer of avascular flat nucleated cells (simple squamous epithelium) which produce the lubricating serous fluid. This fluid has a consistency similar to thin mucus. These cells are bound tightly to the underlying connective tissue.
The connective tissue layer provides the blood vessels and nerves for the overlying secretory cells, and also serves as the binding layer which allows the whole serous membrane to adhere to organs and other structures.

For the heart, the surrounding serous membranes include:

Outer	Inner
Parietal pericardium	Visceral pericardium (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

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

There are three serous cavities and their associated membranes.

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. The pericardium is a two-layered sac that surrounds the entire heart except where the blood vessels emerge on the heart’s superior side.^[2]
The pleura is the serous membrane that surrounds the lungs in the pleural cavity; the pericardium is the serous membrane that surrounds the heart in the pericardial cavity
The peritoneum is the serous membrane that surrounds several organs in the abdominopelvic cavity.

The serous fluid produced by the serous membranes reduces friction between the walls of the cavities and the internal organs when they move, such as when the lungs inflate or the heart beats, that could otherwise lead to inflammation of the organs.^[2]

The serous membranes have two layers, parietal and visceral, surrounding a fluid filled space.^[2]

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 splanchnopleure is associated with the underlying endoderm with which it is in contact, and later becomes the serous membrane in contact with visceral organs within the body.
The somatopleure is associated with the overlying ectoderm and later becomes the serous membrane in contact with the body wall.

The intraembronic 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.

Additional images

Layers of stomach wall
Section of duodenum of cat

References

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

↑ "The Anatomy of Lining and Covering Tissues-Membranes!". McGraw-Hill Companies. Retrieved September 12, 2016.
1 2 3 4 "Anatomy & Physiology". Openstax college at Connexions. Retrieved November 16, 2013.

External links

UIUC Histology Subject 844

Anatomy of the Gastrointestinal tract, excluding the mouth

Upper

Pharynx	Muscles Spaces peripharyngeal retropharyngeal parapharyngeal retrovisceral danger prevertebral Pterygomandibular raphe Pharyngeal raphe Buccopharyngeal fascia Pharyngobasilar fascia Piriform sinus

Esophagus	Sphincters upper lower glands

Stomach	Curvatures greater lesser Angular incisure Cardia Body Fundus Pylorus antrum canal sphincter Gastric mucosa Gastric folds Microanatomy Gastric pits Gastric glands Cardiac glands Fundic glands Pyloric glands Foveolar cell Parietal cell Gastric chief cell Enterochromaffin-like cell

Lower

Small intestine

Microanatomy	Intestinal villus Intestinal gland Enterocyte Enteroendocrine cell Goblet cell Paneth cell

Duodenum	Suspensory muscle Major duodenal papilla Minor duodenal papilla Duodenojejunal flexure Brunner's glands

Jejunum	no substructures

Ileum	Ileocecal valve Peyer's patches Microfold cell

Large

Cecum	Appendix

Colon	Ascending colon Hepatic flexure Transverse colon Splenic flexure Descending colon Sigmoid colon Continuous taenia coli haustra epiploic appendix

Rectum	Transverse folds Ampulla

Anal canal	Anus Anal columns Anal valves Anal sinuses Pectinate line Internal anal sphincter Intersphincteric groove External anal sphincter

Wall

Anatomy of the lower respiratory tract

Respiratory tree

Trachea	Tracheal rings Annular ligaments Carina

Bronchi	Main left right Secondary eparterial Tertiary

Lungs

General	Landmarks Base Apex Root Hilum Fissures Horizontal Oblique Superior lobe Lingula of left lung Middle lobe of right lung Inferior lobe

BP segment	Bronchiole: Conducting zone (Terminal bronchiole) Respiratory zone (Respiratory bronchiole Alveolar duct Alveolus Blood-air barrier)

Cells	Alveolar cells Type I Type II Club cell Goblet cell

Anatomy of the peritoneum and mesentery

General

Abdominal

From ventral mesentery	Lesser omentum Hepatoduodenal ligament Hepatogastric ligament Liver Coronary ligament (Left triangular ligament Right triangular ligament Hepatorenal ligament) Falciform ligament (Round ligament of liver and Ligamentum venosum in it, but not of it)

From dorsal mesentery	Greater omentum Gastrophrenic ligament Gastrocolic ligament Gastrosplenic ligament Mesentery Transverse mesocolon Sigmoid mesocolon Mesoappendix Root of the mesentery Splenorenal ligament Phrenicocolic ligament Folds Umbilical folds Supravesical fossa Medial inguinal fossa Lateral umbilical fold Lateral inguinal fossa Ileocecal fold

Abdominal cavity	Greater sac Lesser sac Omental foramen

General	Cystohepatic triangle Hepatorenal recess of subhepatic space Abdominal wall Inguinal triangle Peritoneal recesses Paracolic gutters Paramesenteric gutters

Pelvic

Uterus/ovaries	Broad ligament of the uterus Mesovarium Mesosalpinx Mesometrium) Ovarian ligament Suspensory ligament of ovary

Recesses	Male Recto-vesical pouch Pararectal fossa Female Recto-uterine pouch Recto-uterine fold (Uterosacral ligament) Vesico-uterine pouch Ovarian fossa Paravesical fossa Retroperitonium

Spaces

This article is issued from Wikipedia - version of the 10/23/2016. The text is available under the Creative Commons Attribution/Share Alike but additional terms may apply for the media files.