Actin-based structures

filament in the cytoplasm of eukaryotic cells

thumb|Amoeba proteus extending lobose pseudopodia|300x300px

Microvilli (: 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, cellular adhesion, and mechanotransduction.

The lamellipodium (: lamellipodia) (from Latin lamella, related to '', "thin sheet", and the Greek radical pod-'', "foot") is a cytoskeletal protein actin projection on the leading edge of the cell. It contains a quasi-two-dimensional actin mesh; the whole structure propels the cell across a substrate. Within the lamellipodia are ribs of actin called microspikes, which, when they spread beyond the lamellipodium frontier, are called filopodia. The lamellipodium is born of actin nucleation in the plasma membrane of the cell and is the primary area of actin incorporation or microfilament formatio

180px|thumb|This electron micrograph shows exaggerated filopodia with club-like shape induced by formin mDia2 in cultured cells. These filopodia are filled with bundled microfilament|actin filaments which were born in and converged from the lamellipodial network.

Stereocilia (or stereovilli or villi) are non-motile apical cell modifications. They are distinct from cilia and microvilli, but are closely related to microvilli. They form single "finger-like" projections that may be branched, with normal cell membrane characteristics. They contain actin. Stereocilia are found in the vas deferens, the epididymis, and the sensory cells of the inner ear.

small region on the surface of a cell that anchors the cell to the extracellular matrix and that forms a point of termination of actin filaments

migrating motile tip of a growing nerve cell axon or dendrite