The propulsion of mucus by cilia

Orientation of respiratory tract cilia in patients with primary ciliary dyskinesia, bronchiectasis, and in normal subjects

A reproducible technique, utilising a graphics tablet and a personal computer for measuring ciliary orientation from electron micrographs of ciliated epithelium, was assessed. Ciliary deviation was measured in 47 normal subjects (mean ciliary deviation +/- 1 SD was 14.6 (3.3 degrees)), in eight patients with bronchiectasis and normal ciliary function (15.1 (6.5 degrees], and in seven patients with primary ciliary dyskinesia (38.7 (7.8 degrees); significantly greater than the first two groups). Measurements of ciliary deviation at the tip, base, and basal feet showed very little variation along the ciliary shaft in all three groups, suggesting that valid measurements of ciliary deviation can be made at any level of the cilium. Mean ciliary deviation in normal subjects was always less than 30 degrees; all patients with a mean ciliary deviation of greater than 30 degrees had recurrent respiratory tract disease. Four of seven patients with primary ciliary dyskinesia had ciliary disorientation; in one this was the only defect. Measurements of inter- and intraobserver variability using this method showed a maximum difference between observations of 4.1 degrees. It is suggested that ciliary orientation should be measured in patients suspected of having defective ciliary function or structure, or both.

Adaptations of ciliary systems for the propulsion of water and mucus

1. The characteristics of ciliary systems are determined by the dominance of viscous effects over inertial effects. 2. The velocity of water propulsion depends on ciliary length, beat frequency, pattern of beating, the arrangement of the cilia and their co-ordination. Beating cilia influence a layer of water only two or three cilium lengths deep, with maximal velocity near the ciliary tip. 3. Mucus is propelled by the tips of short cilia that penetrate the mucus; these cilia are closely spaced on epithelia, and achieve slow propulsion that is relatively independent of load and does not require strong ciliary co-ordination.