Intestinal brush border (None)

The *intestinal brush border* is an ultrastructural specialization on the apical surface of differentiated enterocytes lining the proximal small intestine. It consists primarily of densely packed microvilli approximately ~100 nm in diameter and ~1–3 µm long arranged hexagonally. This architecture increases absorptive surface area by about ninefold up to sixteenfold compared with smooth surfaces[1][3]. Microvilli are interconnected by intermicrovillar adhesion complexes involving protocadherins that maintain structural stability[1]. This dense packing forms a *physical barrier* that prevents luminal microbes from accessing vulnerable epithelial surfaces. When disrupted—such as during inflammation-induced cytoskeletal contraction causing "fanning"—bacteria can penetrate deeper into cells via lipid raft-dependent endocytosis, contributing to diseases like inflammatory bowel disease[1]. Embedded within this membrane are numerous digestive enzymes including glycohydrolases essential for terminal carbohydrate digestion into absorbable monosaccharides[5]. Additionally, critical nutrient transporters reside here such as: - Sodium-glucose cotransporter type I (**SGLT1**) which mediates active glucose uptake coupled with sodium influx, - Sodium-hydrogen exchanger type III (**NHE3**) which regulates intracellular pH and sodium balance, both playing complementary roles regulated reciprocally at transcriptional and functional levels[4][6]. This complex system ensures efficient digestion, selective permeability, host defense against pathogens, while maintaining electrolyte homeostasis crucial for overall intestinal health.

Other names

Brush borderStriated borderMicrovillar membraneApical membrane of enterocytes

Modulation/inhibition/activation of embedded nutrient transporters