According to science writer Clare Smith for SeattlePi, the cell membrane is kept from collapsing by its phospholipid bilayer, maintenance of the correct temperature, a cytoskeleton and cell junctions. These are necessary because the cell membrane is one of the most crucial components of a cell.
Smith goes into detail about these four features of the cell membrane. She describes the phospholipid bilayer as a simultaneously hydrophilic and hydrophobic region. This is due to the molecules that compose the cell membrane. One end of these molecules is attracted to water, while the other end repels water. This effectively prevents anything from entering or exiting the cell.
Smith also describes the necessity of maintaining the correct temperature as being due to the natural fluidity of cell membranes. If a membrane was to drop below a certain temperature, it could freeze, lose this fluidity, and collapse, which would leave the cell vulnerable.
Smith compares the cytoskeleton of a cell membrane to an exoskeleton. It is composed of protein filaments, many of which attach to the phospholipid bilayer and provide structural support. This is especially useful since red blood cells often have to squeeze between cells, which puts a lot of stress on the membrane.
Finally, Smith discusses cell junctions that hold cells together. This final layer of protection has anchors, called desmosomes, holding cells together by connecting to their cytoskeletons.