The terminal web is a structure found at the apical surface of

epithelial cells Epithelium or epithelial tissue is a thin, continuous, protective layer of cells with little extracellular matrix. An example is the epidermis, the outermost layer of the skin. Epithelial ( mesothelial) tissues line the outer surfaces of man ...

that possess microvilli. It is composed primarily of

actin Actin is a family of globular multi-functional proteins that form microfilaments in the cytoskeleton, and the thin filaments in muscle fibrils. It is found in essentially all eukaryotic cells, where it may be present at a concentration of ...

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 mem ...

, 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 many animal and fungal cells. In animals, it is an important component of the muscular system which works in conjunction with troponin to regulate muscle contraction. It ...

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