The terminal web is a filamentous structure found at the apical surface of epithelial cells that possess

microvilli Microvilli (singular: microvillus) are microscopic cellular membrane protrusions that increase the surface area for diffusion and minimize any increase in volume, and are involved in a wide variety of functions, including absorption, secretion, ...

. It is composed primarily of

actin Actin is a protein family, family of Globular protein, globular multi-functional proteins that form microfilaments in the cytoskeleton, and the thin filaments in myofibril, muscle fibrils. It is found in essentially all Eukaryote, eukaryotic cel ...

filaments stabilized by

spectrin Spectrin is a cytoskeletal protein that lines the intracellular side of the plasma membrane in eukaryotic cells. Spectrin forms pentagonal or hexagonal arrangements, forming a scaffold and playing an important role in maintenance of plasma memb ...

, which also anchors the terminal web to the apical cell membrane. The presence of myosin II and

tropomyosin Tropomyosin is a two-stranded alpha-helical, coiled coil protein found in actin-based cytoskeletons. Tropomyosin and the actin skeleton All organisms contain organelles that provide physical integrity to their cells. These type of organelles a ...

helps to explain the contractile ability of the terminal web. When contracted, the terminal web causes a decrease in diameter of the apex of the cell, causing the microvilli, which are anchored into the terminal web through their stiff actin fibers, to spread apart. This spreading apart of the microvilli aids cells in absorption.Ross, Michael H., and Wojciech Pawlina. "Chapter 5: Epithelial Tissue." Histology: a Text and Atlas : with Correlated Cell and Molecular Biology. Philadelphia: Wolters Kluwer/Lippincott Williams & Wilkins Health, 2011. 110. Print.

References

Anatomy {{anatomy-stub