A Quantitative Interspecies Comparison of The Respiratory Mucociliary Clearance Mechanism

Background: Collectively coordinated ciliary activity constantly propels the airway surface liquid, which lines the luminal surface of the vertebrate respiratory system, in cranial direction – constituting mucociliary clearance, the primary defence mechanism of our airways. Our contemporary understanding on how the quantitative characteristics of the metachronal wave field determines the resulting mucociliary transport is still limited, which is partly due to the sparse availability of quantitative observational data. Methods: We employed high-speed video reflection contrast microscopy to simultaneously image and quantitatively characterize the metachronal wave field as well as the mucociliary transport in excised bovine, porcine, ovine, lapine, turkey and ostrich samples of the luminal tracheal wall. Advanced image processing techniques were used to determine the ciliary beating frequency (CBF), the velocity and the wavelength of the metachronal wave as well as the mucociliary transport velocity. Results: The mucociliary transport direction was found to strongly correlate with the mean wave propagation direction in all six species. The CBF yielded similar values (10−15 Hz) for all six species. Birds were found to exhibit considerably higher transport speeds (130−260 μm/s) than mammals (20−80 μm/s). While the average transport direction significantly deviates from the tracheal long axis (TLA) in mammals, no significant deviation from the TLA was found in birds. In comparison to mammals, longer metachronal wavelengths were found in birds. Finally, the metachronal waves were found to propagate at about 4−8 times the speed of mucociliary transport in mammals, whereas the metachronal waves propagate at about the speed of mucociliary transport in birds. Conclusions: The tracheal mucociliary clearance mechanism is based on a symplectic metachronsim in all examined species. The mucociliary transport in birds is fast and roughly follows the TLA, whereas the transport is slower and proceeds along a left-handed spiral in mammals. The longer wavelengths and the lower ratio between the metachronal wave speed and the mucociliary transport speed provide further evidence that the mucociliary clearance mechanism operates differently in birds than in mammals.

Heat Transfer Analysis of MHD Viscous Fluid in A Ciliated Tube with Entropy Generation

This investigation aims to explain the study of heat transfer and entropy generation of magnetohydrodynamic (MHD) viscous fluid flowing through a ciliated tube. Heat transfer study has massive importance in various biomedical and biological industry problems. The metachronal wave propagation is the leading cause behind this viscous creeping flow. A low Reynolds number is used as the inertial forces are weaker than viscous forces, and also creeping flow limitations are fulfilled. For the cilia movement, a very large wavelength of a metachronal wave is taken into account. Entropy generation is used to examine the heat transfer through the flow. Exact mathematical solutions are calculated and analyzed with the help of graphs. Streamlines are also plotted.

Thermal analysis of airway mucus clearance by ciliary activity in the presence of inertial forces

In this study heat transfer effects on cilia induced mucus flow in human airways is presented. The elliptic wave pattern of cilia tips produces metachronal wave which enables the transportation of highly viscous mucus with nonzero inertial forces. Upper Convective Maxwell model is considered as mucus. The governing partial differential equations are transformed from the fixed frame to the wave frame by using Galilean transformation and viscous dissipation is also incorporated in the energy equation. The non-linear governing equations are evaluated by the perturbation technique by using software “MATHEMATICA” and pressure rise is computed by numerical integration. The impact of interested parameters on temperature profile, velocity, pressure rise and pressure gradient are plotted by the graphs. The comparison of velocities due to symplectic and antiplectic metachronal wave are also achieved graphically.

Mathematical Modeling of Mucociliary Clearance: A Mini-Review

Mucociliary clearance is an important innate host defense of the mammalian respiratory system, as it traps foreign substances, including pollutants, pathogens, and allergens, and transports them out of the airway. The underlying mechanism of the actuation and coordination of cilia, the interplay between the cilia and mucus, and the formation of the metachronal wave have been explored extensively both experimentally and mathematically. In this mini-review, we provide a survey of the mathematical models of mucociliary clearance, from the motion of one single cilium to the emergence of the metachronal wave in a group of them, from the fundamental theoretical study to the state-of-the-art three-dimensional simulations. The mechanism of cilium actuation is discussed, together with the mathematical simplification and the implications or caveats of the results.