Overview

Digestion is completed and metabolites are absorbed in the small intestine.  The small intestine, composed of a mucosa, submucosa, muscularis externa and usually a serosa, is subdivided into duodenum, jejunum and ileum.  The exocrine secretions of the pancreas and liver are released into the duodenum.  10x

Digestion is completed and metabolites are absorbed in the small intestine.  The small intestine, composed of a mucosa, submucosa, muscularis externa and usually a serosa, is subdivided into duodenum, jejunum and ileum.  The exocrine secretions of the pancreas and liver are released into the duodenum.  10x

Villi are finger-like projections from the surface of the small intestine into the lumen of the organ.  Villi are composed of a central core of lamina propria covered by its overlying surface epithelium.  The presence of villi are diagnostic for the small intestine.

Digestion is completed and metabolites are absorbed in the small intestine.  The small intestine, composed of a mucosa, submucosa, muscularis externa and usually a serosa, is subdivided into duodenum, jejunum and ileum.  The exocrine secretions of the pancreas and liver are released into the duodenum.  10x

Plicae circulares are circular folds extending around the inner circumference of the small intestine.  The central core of each plica, formed by the submucosa, pushes up all the overlying layers.  Therefore, the entire mucosa (including villi and glands) overlying the submucosal core is included in each plica.

The muscularis externa of the small intestine is composed of inner circular and outer longitudinal layers of smooth muscle, similar to other regions of the digestive tract.

The outermost layer of the small intestine may be either an adventitia (in the part of the duodenum that is retroperitoneal) or a serosa, in the remainder of the duodenum and in the jejunum and ileum (shown here).  (See serosa and adventitia in the General Concepts chapter to review where each is present.)

The mesentery suspends most of the small intestine from the dorsal body wall.  It is composed of two serosal layers and an intervening layer of loose connective tissue.

The mesentery suspends most of the small intestine from the dorsal body wall.  It is composed of two serosal layers and an intervening layer of loose connective tissue.