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Diagram showing the anatomy of the small intestine with labeled regions (duodenum, jejunum, ileum), a cross-section highlighting muscle and mucosa layers, an enlargement of mucosal folds (plicae circulares), and a detailed view of a villus structure with epithelial, goblet, endocrine, and Paneth cells, microvilli, blood capillaries, and lacteal.
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Diagram showing the anatomy of the small intestine with labeled regions (duodenum, jejunum, ileum), a cross-section highlighting muscle and mucosa layers, an enlargement of mucosal folds (plicae circulares), and a detailed view of a villus structure with epithelial, goblet, endocrine, and Paneth cells, microvilli, blood capillaries, and lacteal.
structures of the small intestine The inner wall of the small intestine is covered by numerous folds of mucous membrane called plicae circulares. The surface of these folds contains tiny projections called villi and microvilli, which further increase the total area for absorption. Absorbed nutrients are moved into circulation by blood capillaries and lacteals, or lymph channels.

The brush border is a layer of microvilli found on the surface of certain epithelial cells, most notably those lining the kidney tubules and the small intestine. These microvilli are tiny, bristle-like protrusions that significantly increase the surface area of the cell.12

In the small intestine, the brush border plays a crucial role in digestion and absorption. It enlarges the absorptive surface area of the intestinal lining by about 25 times, facilitating the uptake of nutrients and water. The microvilli also secrete enzymes like disaccharidase and peptidase, which break down complex carbohydrates and proteins into simpler forms that can be absorbed. This specialized structure is essential for efficient nutrient absorption in the digestive system.32

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3 Britannica Sources
  1. brush border
  2. human digestive system - Absorption
  3. microvillus

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