Page 589 - Atlas of Histology with Functional Correlations
P. 589

as regular and dense finger-like extensions of the absorptive cell cytoplasm. The

               microvilli are coated by a glycoprotein coat (glycocalyx), which contains brush
               border  enzymes.  The  microvilli  increase  the  absorptive  luminal  surface  area
               many fold.



               Glands,  Cells,  and  Lymphatic  Cells  and  Nodules

               in Small Intestine




               Intestinal Glands



               Located  throughout  the  small  intestine  are  the  intestinal  glands  (crypts  of
               Lieberkühn). These glands open into the intestinal lumen at the base of the villi.
               The simple columnar epithelium that lines the villi is continuous with that of the
               intestinal  glands  that  contain  regenerative  stem  cells,  absorptive  cells,  goblet

               cells, Paneth cells, and enteroendocrine cells.


               Intestinal Cells



                   Absorptive  cells  are  the  most  common  cells  in  the  intestinal  epithelium.

                   These  cells  are  tall  and  columnar  with  a  prominent  brush  border  of
                   microvilli. A thick glycocalyx coat covers and protects the microvilli from
                   the corrosive digestive chemicals.
                   Goblet  cells  are  interspersed  among  the  columnar  absorptive  cells  of  the

                   epithelium.  They  increase  in  number  toward  the  distal  region  of  the  small
                   intestine (ileum).
                   Enteroendocrine  or  diffuse  neuroendocrine  system  (DNES)  cells  are
                   scattered throughout the epithelium of the villi and intestinal glands.

                   Duodenal (Brunner) glands are primarily found in the submucosa of the
                   initial  portion  of  the  duodenum  and  characterize  this  region  of  the  small
                   intestine.  These  are  branched,  tubuloacinar  glands  with  light-staining
                   mucous  cells.  The  ducts  of  duodenal  glands  penetrate  the  muscularis

                   mucosae  and  discharge  their  secretory  products  at  the  base  of  intestinal
                   glands located between the villi.
                   Undifferentiated or stem cells are located at the base of intestinal glands,
                   and they exhibit increased mitotic activity. These stem cells replace all worn-

                   out columnar absorptive cells, goblet cells, and intestinal gland cells in the
                   small intestine.



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