Structure of a cilium - digitally enhanced

Cilia and flagella both have this structure at their core which is known as the axoneme. Each axoneme is composed of a circular arrangement of nine pairs of microtubules around a single pair in the centre. This is commonly called the 9 + 2 arrangement. Several other proteins are associated with the microtubules and either hold the axoneme together or control the sliding of the paired microtubules past each other. This sliding causes the bending movements of the cilla.