Fig 9. Diagrams schematically depicting the relationships between tensions (shown per cell) and contact angles at tissue surfaces (top) and at interstitial gaps (triangles).
(A) In normal CM, cortical tension β at the tissue surface (black) is strongly reduced upon cell adhesion to tension βf (red). Release of binding energy due to adhesion factor interactions at the narrow CM contacts generates an adhesion tension Γ/2 (green). Tensions βf and Γ/2 balance the resultant tension βc (grey); surface contact angle, θs. The same tensions βf and Γ/2 act at the transition to interstitial gaps, but at the gap surface not β but the much smaller βf balance these tensions (orange), requiring a much smaller contact angle θ. (B) In C-cad morphants, tension β at the free surface remains; at contacts tension it is much less diminished. In the width range of normal CM, Γ/2 may remain the same, contact angle θ becomes smaller, and the relative adhesiveness α appears reduced. (C) When the average Γ/2 is increased with contact width much beyond the normal CM range, the contact angle θ at gaps can remain the same or even increase while a lowered angle θs at the surface still indicates the reduced overall adhesion strength (the difference σ = β − βc) due to C-cad depletion.