Cytoskeleton

Present in the cytoplasm of all cells, the cytoskeleton is the term used to describe the system of filaments and fibres, essential in maintaining the shape and internal organisation of the cell. The cytoskeleton is made up of three key elements: actin filaments, intermediate filaments and microtubules. These interlinking protein filaments form a complex and dynamic network functioning to give structure to the cell, and to move intracellular molecules and organelles.
The primary function of the cytoskeleton within the cell is to maintain the cells physical shape. Contractions of the cytoskeleton allow for cell mobility and its elastic properties prevent permanent deformation. Additionally, the cytoskeleton is essential in intracellular transport, involved in cell signalling pathways and the endocytosis of extracellular material. Movement of vesicles, organelles or cellular molecules is entirely dependent the cytoskeleton.
In specialised cells, the cytoskeleton can form additional structures such as flagella or cilia, allowing for increased cellular mobility and specific tasks to be undertaken. Alternatively, highly specialised cytoskeletons of multiple cellular units can act together to undertake large scale processes such as muscle contraction.