Primary cilia link mechanosensory, visual, osmotic, gustatory and other stimuli to mechanisms of cell-cycle control and epithelial cell polarity.

The architecture of the microtubule backbone distinguishes motile cilia, in which nine doublets of microtubules surround a central pair (9+2), from primary cilia, in which the central pair of microtubules is absent (9+0).

See also

 motile cilia and flagella

References

 Davenport JR, Yoder BK. An incredible decade for the primary cilium: a look at a once-forgotten organelle. Am J Physiol Renal Physiol. 2005 Dec;289(6):F1159-69. PMID: #16275743#

 Pan J, Wang Q, Snell WJ. Cilium-generated signaling and cilia-related disorders. Lab Invest. 2005 Apr;85(4):452-63. PMID: #15723088#