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Intestinal Folding: Villi & Microvilli
Small intestine (specifically the duodenum)
  • Major site of nutrient absorption.
Three folded mucosal structures maximize surface area for absorption* 1 - Plicae circulares: wavy, folds on the inner walls of small intestine to form circular folds that increase surface area 3-fold. 2 - Villi: finger-like projections that protrude from the plicae circulares that increase surface area by 10-fold. Arterioles, venules, and lymphatic vessels pass through the villi and uptake absorbed nutrients. 3 - Microvilli (brush border): hair-like projections on columnar small intestine epithelial cells (face the lumen of the small intestine) that increase surface are 20-fold. Together, all folded layers = 600-fold surface area increase
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Intestinal Folding: Villi & Microvilli

Small Intestine Folding
  • Plicae ciculares are wavy, folds on the inner walls of the tube
    • Form circular folds.
    • Increase the surface area of the small intestine 3-fold.
  • Villi are finger-like projections that protrude from the plicae circulares.
    • Increase the small intestine surface area by 10-fold.
    • Arterioles, venules, and lymphatic vessels pass through the villi and uptake absorbed nutrients.
  • Microvilli, also called the brush border, are hair-like projections that face the lumen of the small intestine.
    • Increase the small intestine surface area by 20-fold.
  • All together, these folded layers produce a 600-fold increase in the surface area of the small intestine!

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