The microfluidics of cilia motion

Cilia are practically omnipresent in the human body and play a major role in a multitude of processes: from the regulation of left-right asymmetry in developmental biology, to lung disease, pollution and drug delivery, they correspond to a very efficient microfluidics activator. Of particular interest to us are cilia encountered in the node, the precursor of the heart in mammalian development, and in the lungs.

Nodal cilia develop during the first stages of gestation in vertebrates. Cilia located in the node itself are capable of rotation, generating a directional extra-embryonic fluid flow. At the same time, others, distributed around the peripheral region sense this flow (possibly mechanically) and translate this information into chemical signals, via the deformation of the ciliary shaft. This directional signaling contributes to the early left and right specification of the embryos, which is crucial for the proper development of vertebrates' body geometry.

Active and passive cilia simulation in the nodal system

The respiratory cilia in our lungs serve a different function. Rather than rotating, these hair-like structures beat in an almost two-dimensional plane. The effective bending of cilia induces an upwards movement of the aqueous and mucus layers that covers above them, which helps our bronchi remove secretions and particle depositions, reduce the respiratory tract infections, and therefore, defend our respiratory system.

Media:
(Movie, 3 Mb). Motion and velocity of an active-passive cilium system.
(Movie 30 Mb). Effective and recovery stroke of a beating lung cilium, streamlines and pressure.
(Movie, 13 Mb). Motion and tip trajectory of an active-passive cilium system.