Tunica serosa

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As the tunica serosa (also serosa ) is called the smooth lining of the thoracic cavity ( Cavitas pleuralis ), peritoneal cavity ( peritoneal cavity ) and the pericardium ( Cavitas pericardialis ). It is shiny, transparent and covered by a film of liquid to allow the internal organs to move easily. In contrast to the tunica adventitia , it has an epithelial layer (mesothelium). The tunica serosa can limit the spread of inflammation.


The serosa consists of two to three layers:

Lamina epithelialis serosae

The outer layer facing the body cavity consists of a single-layer squamous epithelium , the serosa epithelium. It comes from the mesodermal coelom epithelium, and is therefore also mesothelium called. There are pores between the mesothelial cells through which fluid can enter and exit. The mesothelium is both secretory and absorptive . The serous fluid film is also a product of the mesothelium.

Lamina propria serosae

The connective tissue lamina propria serosae lies beneath the epithelium . The blood and lymph vessels and nerves run in this layer . In addition, there are cells of the immune system in the lamina propria , which are called milk spots ( macula lactea ).

Tela subserosa

The connective tissue Tela subserosa acts as a shifting layer on organs whose filling level and extent vary, e.g. B. the urinary bladder or the stomach . Adipose tissue can be stored in this layer .

Regional breakdown

The serosa is called differently in the body cavities:


The serosa not only lines the wall of the body cavities. The organs located in the cavities turn inside out into this skin, as if you put an object on a foil and wrapped it in it. Therefore, all organs in the body cavities have a serosa coating that is closely connected to the organ surface and gives it a shiny appearance.

The resulting double lamella ( serosal duplication ) between the wall sheet of the serosa and the organ is called the mesentery ( mesentery ). It is used to fasten the internal organs. The respective mesentery is named with the prefix meso and the respective Latin organ name, such as B. Mesoduodenum (mesentery of the duodenum ) or mesorchium (mesentery of the testicle ). For some organs special names have been used, e.g. B. Ligamentum latum uteri ( uterine mesentery ).

Big and small network

A special form of the mesentery are nets (Latin omenta , Greek epiploon ). Here the double lamella is extended. This involves remodeling of the two gastric mesenteries ( mesogastrium dorsal and ventral ). In mammals including humans there is one

  • Omentum minus ("small network"): between the liver , stomach and duodenum , somewhat artificially divided into the ligamentum hepatogastricum and ligamentum hepatoduodenale
  • Omentum majus ("large net"): as an apron of fatty tissue hanging down from the stomach over the transverse bowel to the level of the navel.

In some animals (e.g. horses ) the greater omentum lies between the intestinal loops.

Special educations

Serosa duplicates can also circulate directly between neighboring organs. Such serosa bridges are called

  • Ligament ( ligament ), e.g. B. Ligamentum cecocolicum (not to be confused with the purely connective tissue ligaments on joints , which are also called "ligamentum")
  • Plica , e.g. B. Plica ileocaecalis

In some cases, “ligament” is also used for serosal duplicates between the organ and the abdominal wall (e.g. ligamentum ovarii proprium , liver ligaments), in some cases also for sections of mesenteries (see above under “small mesh”).


  1. ^ V. Schumpelick et al.: Short textbook on surgery. ISBN 3-13-127127-2 , p. 433.