Figure 1.

Elements and mechanics of MCC. (a) Brush-on-gel model of MCC: goblet cells produce gel-forming mucins that constitute the mucus layer as well as brush forming mucins in the PCL that tether to cell membranes. Multiciliated cells propel the mucus layer during the power stroke (black solid arrow) and move through the PCL during the recovery stroke (black dashed arrow) to achieve directional mucociliary clearance (orange solid arrow). (b) Important structure–function relationships of MCC at cellular and tissue level, including ciliary beat kinematics which depend on ciliary ultrastructure; metachronal beat facilitated by hydrodynamic coupling (HC) and, in interaction with the ASL rheology, leading to fluid flow; and rotational and tissue-level polarity of ciliary beat which is modulated by planar cell polarity (PCP) signalling, mechanical coupling (MC) of cytoskeletal elements and potentially the feedback from directional fluid flow forces. (Online version in colour.)