CorpusHuman Anatomy
Cells & TissuesOrganelle

Microvilli

Microvillus (pl. microvilli)

Also known as: microvillus, brush border, striated border, stereocilia

Finger-like, actin-supported projections of the apical plasma membrane (≈1 µm tall) that multiply the absorptive surface of epithelial cells, forming the brush border.

Intestinal Villus and Absorption Smell and Taste — Chemoreceptors The Eukaryotic Cell

Overview

Height × width≈1–2 µm × 0.08–0.1 µm
Actin filaments per core≈20–30
Surface amplification≈20×

Each microvillus is ≈0.08–0.1 µm wide and ≈1–2 µm tall and contains a core bundle of 20–30 parallel actin filaments, cross-linked by villin and fimbrin and tethered laterally to the membrane by myosin I. The bundles are anchored below in the terminal web, a horizontal meshwork of actin, spectrin and keratin intermediate filaments. Thousands of closely packed microvilli on an absorptive cell increase its apical surface about 20-fold. Their glycocalyx carries digestive enzymes (disaccharidases, peptidases) and transporters.

In light microscopy densely packed, uniform microvilli appear as a striated border (small-intestinal enterocytes) or brush border (proximal convoluted tubule). Stereocilia are unusually long, non-motile, sometimes branched microvilli — not cilia — found in the epididymis and ductus deferens (absorption) and, as the precisely graded mechanosensory bundles, on inner-ear hair cells. Short, irregular microvilli occur on many other cells.

Location

Small and large intestinal enterocytes, proximal convoluted tubule, gallbladder, placenta (syncytiotrophoblast), epididymis (stereocilia), inner-ear hair cells (stereocilia).

Anatomy

Histology

A fine, eosinophilic, PAS-positive apical band — the striated or brush border — beneath which the terminal web forms a clear zone. Unlike cilia, individual microvilli are not resolvable by light microscopy.

Function

  • Increase surface area for absorption.
  • Carry membrane-bound digestive enzymes (brush-border enzymes) and transporters.
  • Mechanotransduction (hair-cell stereocilia).

Clinical significance

Coeliac disease

Immune reaction to gluten flattens intestinal villi and damages enterocyte microvilli → malabsorption, reduced brush-border enzyme activity (secondary lactose intolerance), iron-deficiency anaemia.

Microvillus inclusion disease

Rare autosomal recessive MYO5B mutation: microvilli fail to reach the apical surface and appear in intracellular inclusions → intractable watery diarrhoea from birth.

Compiled from standard anatomy and physiology references — see the Cells & Tissues sources. For education only; not medical advice.