A normal cell in a hypotonic solution will swell due to osmosis and may lyse if too much water flows into it. This is because the plasma membrane can no longer contain the additional volume. Microvilli have a relatively high ratio of surface area (membrane) to volume and look like tines of a comb on the cell surface. This additional membrane means that the cell can expand more without bursting.
Microvilli are hair-like structures that protrude from the cell membrane. Their primary function is to increase the surface area of the cell for activities such as digestion, absorption and secretion. They do not directly play a role in cell lysis because water can move via osmosis through the cell membrane. However, there are studies suggesting that microvilli may influence the electrostatic environment of the cell.