基体（kinetosome），又称毛基体，真核细胞的纤毛或鞭毛基底部由微管及其相关蛋白质构成的短筒状结构。与中心粒的结构十分相似，负责轴丝的生长和鞭毛与纤毛的合成。

9个外围纤维在进入细胞质内形成一筒状结构，每根外围纤维变成3个亚纤维，成车轮状排列。而中心纤维在进入细胞质之前终止。基体向细胞内伸出纤维称为根丝体，终止在细胞核或其附近。基体的结构与中心粒相似，在细胞分裂时，基体也可起中心粒的作用。纤毛由于数量很多，在基体之间都有动纤丝相联，构成一个下纤列系统进行纤毛间的协调动作。

A basal body (synonymous with basal granule, kinetosome, and in older cytological literature with blepharoplast) is a protein structure found at the base of a eukaryotic **** (cilium or flagellum). It is formed from a centriole and several additional protein structures, and is, essentially, a modified centriole. Basal body serves as a nucleation site for the growth of the axoneme microtubules. Centrioles, from which basal bodies are derived, act as anchoring sites for proteins that in turn anchor microtubules, and are known as the microtubule organizing center (MTOC). These microtubules provide structure and facilitate movement of vesicles and organelles within many eukaryotic cells.