Morphological relationships of SCCs in the airways. A. Schematic representation of a sagittal section through the head of a mouse showing the airways and position of the different micrographs (green, blue and red rectangles). B & C. SCCs in the nasal respiratory epithelium. SCCs expressing TrpM5 or Tas1R3 (driven GFP) are intimately innervated by nerve fibers immunoreactive for PGP9.5 (B) or peptidergic nerve fibers of the trigeminal nerve immunoreactive for CGRP (C). D & E. In the larynx, Tas1R3-GFP+ SCCs are richly innervated by peptidergic (Substance P-immunoreactive) fibers probably from the superior laryngeal nerve (branch of the vagus) which shows responses to chemicals applied to the larynx [5, 50]. F. SCCs of the trachea as shown by TRPM5-driven GFP are not closely embraced by nerve fibers although occasional en passant contacts can be observed.