The structure of a cilium.

Bundle of microtubules and associated proteins that forms the core of cilia and flagella in a eucaryotic cell and is responsible for their movements.

Numerous eukaryotic cells carry whip-like appendages (cilia or eukaryotic flagella) whose inner core consists of a highly-conserved cytoskeletal structure called the axonem. The axoneme serves as the "skeleton" of these organelles, both giving support to the structure and, in most cases, causing it to bend. Though distinctions of function and/or length may be made between cilia and flagella, the internal structure of the axoneme is common to both.