Structure/Morphology
The first 2.5 cm of the duodenum is intraperitoneal, thus is covered by a serosa (i.e., visceral peritoneum). As it becomes retroperitoneal, only the anterior surface of the duodenum is covered by a serosa, with the remaining covered by adventitia. The jejunum and ileum are covered by a serosa.
Key Features/Anatomical Relations
The serosa of the small intestine is the outermost layer of the small intestine. It encloses the jejunum and ileum, except at the mesenteric borders, where the serosa is reflected onto the mesentery.
The deep surface of the serosa adheres to the longitudinal muscular layer of the small intestine. The superficial surface of the serosa is an epithelium or mesothelium, which is in contact with surrounding organs or the parietal peritoneum.
Function
The serosa of the small intestine secretes a serosal fluid. This fluid allows the small intestine to slide across neighboring tissues without creating friction and damage.
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Serosa
The serosa is a thin sheet of connective tissue that contains blood and lymphatic vessels, and is covered by the peritoneum.
