A Theoretical And Experimental Study On Tracheal Muco-Ciliary Transport

Abstract

A series of experiments have been carried out to investigate the muco-ciliary transport in the trachea of rat, rabbit and chicken with cinemicrographic analyses of the movement, beat pattern and metachrony of the tracheal cilia. As a principal test case of the cilia-tip-penetration-into-mucus hypothesis, detailed studies have been made on the transport of a biochemically viable mucous plug artificially introduced into the chicken trachea both with and without a pressure differential across the mucous plug. Guided by the result of these pilot experiments, a theoretical two-layer model of the muco-ciliary transport is introduced, in which the cilia are assumed to penetrate shallowly into the overlaying mucous layer during the effective stroke and to withdraw from the mucous layer during the recovery stroke. Both the mucus and the serous fluid are assumed to be Newtonian and with widely differ ing viscosities. Based on this model the mucus transport rate is found to depend linearly on the ciliary beat frequency and also on the time of ciliary tip penetration in the mucus. Results are also given on the propulsive force contributed by each individual cilium and an estimate of shear and shear rates within the mucous layer.

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