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Extract: High speed cinemicrographs reveal that the ciliary configuration and beat pattern of rabbit tracheal cilia differ significantly from classic descriptions, although the basic forward and return pattern is still observed. The tracheal cilia are short and stout (about 6 μm in length) and are of a slightly bent original configuration. At the start of the forward stroke, the cilia bear about 75–90° to the epithelial surface in the direction of the forward stroke. The forward stroke is planar and consists of a simple “bowing” movement, without showing any progressive bending and without changing the original ciliary configuration. The complete forward stroke sweeps through an arc of about 35–40°, with the tips of the cilia penetrating the bottom of the mucous layer through an arc of about 5–8° at the start of each forward stroke. The return stroke starts from close to the epithelial surface and returns to the starting position of the forward stroke by reversing the planer forward pathway at a reduced speed. The stout nature of the cilia, the original bent ciliary configuration, the near vertical starting position of the forward stroke, the extent of the angular sweeps of the strokes, the peculiar “bowing” forward stroke movement, and the nature of the return stroke all serve to enhance efficiency in moving fluid forward. It has been documented that each forward stroke of the tracheal cilia causes and maintains a swift forward movement of the intermediate serous (liquid) layer of the mucociliary system. This movement, in turn, reacts hydrodynamically with the top mucous layer, and together with the clawing action of the tips of the cilia at the start of the forward stroke, causes the mucous layer to move cephalad in the manner of a conveyor belt. Speculation: This research report describes a method by which the ciliary activity of live rabbit tracheal cilia is documented. The exact ciliary beat pattern can then be determined and the clearance mechanism of tracheal mucus better understood. It is speculated that tracheal mucus stagnation in cystic fibrosis may be a hydromechanical and biochemical problem rather than a direct cilia control problem. Detailed analysis of the ciliary beat pattern and mucus clearance of the tracheal mucociliary system may serve to provide a reference baseline to investigate the possible physiologic effects of cystic fibrosis serum on ciliated epithelial cells (such physiologic effects will be dealt with in a separate report). |
