axoneme

thumb|Electron micrograph of a thin cross-section through two Chlamydomonas axonemes thumb|A simplified model of intraflagellar transport.

In molecular biology, an axoneme is the microtubule-based cytoskeletal structure that forms the core of a cilium or flagellum. Cilia and flagella are found on many eukaryotic cells, including both multicellular organisms and unicellular microorganisms. Motor proteins are attached to the axoneme of many cilia and flagella whose action causes periodic bending to drive cell swimming or motion of surrounding fluid, although not all cilia have motor proteins and can be unable to move. Though distinctions of function and length may be made between cilia and flagella, the internal structure of the axoneme is common to both.