Science, Tech, Math › Science Cytoskeleton Anatomy Share Flipboard Email Print DR GOPAL MURTI/Getty Images Science Biology Anatomy Basics Cell Biology Genetics Organisms Physiology Botany Ecology Chemistry Physics Geology Astronomy Weather & Climate By Regina Bailey Biology Expert B.A., Biology, Emory University A.S., Nursing, Chattahoochee Technical College Regina Bailey is a board-certified registered nurse, science writer and educator. Her work has been featured in "Kaplan AP Biology" and "The Internet for Cellular and Molecular Biologists." our editorial process Regina Bailey Updated August 21, 2019 The cytoskeleton is a network of fibers forming the "infrastructure" of eukaryotic cells, prokaryotic cells, and archaeans. In eukaryotic cells, these fibers consist of a complex mesh of protein filaments and motor proteins that aid in cell movement and stabilize the cell. Cytoskeleton Function The cytoskeleton extends throughout the cell's cytoplasm and directs a number of important functions. It helps the cell maintain its shape and gives support to the cell.A variety of cellular organelles are held in place by the cytoskeleton.It assists in the formation of vacuoles.The cytoskeleton is not a static structure but is able to disassemble and reassemble its parts in order to enable internal and overall cell mobility. Types of intracellular movement supported by the cytoskeleton include transportation of vesicles into and out of a cell, chromosome manipulation during mitosis and meiosis, and organelle migration.The cytoskeleton makes cell migration possible as cell motility is needed for tissue construction and repair, cytokinesis (the division of the cytoplasm) in the formation of daughter cells, and in immune cell responses to germs.The cytoskeleton assists in the transportation of communication signals between cells.It forms cellular appendage-like protrusions, such as cilia and flagella, in some cells. Cytoskeleton Structure The cytoskeleton is composed of at least three different types of fibers: microtubules, microfilaments, and intermediate filaments. These fibers are distinguished by their size with microtubules being the thickest and microfilaments being the thinnest. Protein Fibers Microtubules are hollow rods functioning primarily to help support and shape the cell and as "routes" along which organelles can move. Microtubules are typically found in all eukaryotic cells. They vary in length and measure about 25 nm (nanometers) in diameter.Microfilaments or actin filaments are thin, solid rods that are active in muscle contraction. Microfilaments are particularly prevalent in muscle cells. Similar to microtubules, they are typically found in all eukaryotic cells. Microfilaments are composed primarily of the contractile protein actin and measure up to 8 nm in diameter. They also participate in organelle movement.Intermediate filaments can be abundant in many cells and provide support for microfilaments and microtubules by holding them in place. These filaments form keratins found in epithelial cells and neurofilaments in neurons. They measure 10 nm in diameter. Motor Proteins A number of motor proteins are found in the cytoskeleton. As their name suggests, these proteins actively move cytoskeleton fibers. As a result, molecules and organelles are transported around the cell. Motor proteins are powered by ATP, which is generated through cellular respiration. There are three types of motor proteins involved in cell movement. Kinesins move along microtubules carrying cellular components along the way. They are typically used to pull organelles toward the cell membrane.Dyneins are similar to kinesins and are used to pull cellular components inward toward the nucleus. Dyneins also work to slide microtubules relative to one another as observed in the movement of cilia and flagella.Myosins interact with actin in order to perform muscle contractions. They are also involved in cytokinesis, endocytosis (endo-cyt-osis), and exocytosis (exo-cyt-osis). Cytoplasmic Streaming The cytoskeleton helps to make cytoplasmic streaming possible. Also known as cyclosis, this process involves the movement of the cytoplasm to circulate nutrients, organelles, and other substances within a cell. Cyclosis also aids in endocytosis and exocytosis, or the transport of substance into and out of a cell. As cytoskeletal microfilaments contract, they help to direct the flow of cytoplasmic particles. When microfilaments attached to organelles contract, the organelles are pulled along and the cytoplasm flows in the same direction. Cytoplasmic streaming occurs in both prokaryotic and eukaryotic cells. In protists, like amoebae, this process produces extensions of the cytoplasm known as pseudopodia. These structures are used for capturing food and for locomotion. More Cell Structures The following organelles and structures can also be found in eukaryotic cells: Centrioles: These specialized groupings of microtubules help to organize the assembly of spindle fibers during mitosis and meiosis.Chromosomes: Cellular DNA is wrapped in thread-like structures called chromosomes.Cell Membrane: This semi-permeable membrane protects the integrity of the cell.Golgi Complex: This organelle manufactures, stores, and ships certain cellular products.Lysosomes: Lysosomes are sacs of enzymes that digest cellular macromolecules.Mitochondria: These organelles provide energy for the cell.Nucleus: Cell growth and reproduction are controlled by the cell nucleus.Peroxisomes: These organelles help to detoxify alcohol, form bile acid, and use oxygen to break down fats.Ribosomes: Ribosomes are RNA and protein complexes that are responsible for protein production via translation.