Small Intestine

Small Intestine

1. Niche cells

   • pericryptal fibroblast (mesenchymal cell)
   • myofibroblasts
   • signals

2. Epithelium

   • Crypt
     • Quiescent cell zone (+4 location)
     • active stem cell zone (+1 to +4 positions)
       • LGR5+ crypt base columnar (CBC) intestinal stem cells (ISC)
         • LGR5+ Label retaining cells (LRCs)
           • Paneth cell
         • +4 stem cells
         • DLL-1+ secretory progenitor
           • Secretory cells
             • enteroendocrine cells
             • Goblet cells
             • Tuft cells
         • Absorptive progenitor
           • Transit-amplifying (TA) absorptive enterocytes cells
     • Express noggin
       • counteracts BMP effect
         • High Wnt, low BMP
   • villlus
     • High BMP, low Wnt
   • HH signaling
     • activate expression of BMP
       • feedback repression of Wnt signaling

3. Stroma

   • Stromal cells
     • signals