Terminal web

Definition
noun
(cell biology) The subapical zone rich in microfilaments, and acts as the attachment point for the bundles of apical filaments within microvilli on specialized epithelial cells
Supplement
The terminal web is a zone or a region located at the base of the microvilli in certain specialized epithelial cells (such as intestinal epithelial cells). The name is derived from the web (meshwork) of microfilaments that compose this region. The web of microfilaments is from the bundles of apical filaments at the core of a microvillus as well as from adherens junctions in myosin and in other proteins characteristic of an actomyosin motor system. The actin filaments in the terminal web are stabilized by spectrin. They anchor the terminal web to the apical cell membrane. The contractile ability of the terminal web is due to the presence of myosin II and tropomyosin. It is observed that the contraction at the terminal web results in the decrease in the diameter of the apex of the cell. This, in turn, causes the microvilli to spread apart, which is essential during absorption.^1,2,3
See also:

• microvillus
• epithelial cell
• actin filament
• microfilament

Reference(s):

¹ Hirokawa, N., Tilney, L.G., Fujiwara, K., and Heuser, J.E. (1982). “Organization of actin, myosin, and intermediate filaments in the brush border of intestinal epithelial cells.” . J Cell Biol 94 (2): 425–43. doi:10.1083/jcb.94.2.425.

² Keller, T.C. 3rd, Mooseker, M.S. (1982). “Ca++-calmodulin-dependent phosphorylation of myosin, and its role in brush border contraction in vitro.” J Cell Biol 95 (3): 943–59.

³ Keller, T.C. 3rd, Conzelman, K.A., Chasan, R., Mooseker, M.S. (1985). “Role of myosin in terminal web contraction in isolated intestinal epithelial brush borders.” . J Cell Biol 100 (5): 1647–55. doi:10.1083/jcb.100.5.1647.