Figure 2.

Vagal villus afferents illustrating details of typical trajectories followed by these afferents. A: A low-power montage of a fiber coursing through the smooth muscle wall (extreme lower right of image), dividing at the point, and then issuing a secondary neurite that breaks into three collaterals directed into a cone-shaped villus. Two of the collaterals can be seen ascending to roughly the midpoint of the villus, where they begin to ramify into a terminal arbor. This terminal arbor is somewhat truncated in the present case, because the apical tip of this wedge- or cone-shaped villus is located in adjacent section, and the arbor that can be seen is located in a “shoulder” of the villus. (The third collateral, at the far left, has been interrupted, but continued into the apex of the villus on an adjacent tissue section. The fourth collateral, which separates even as it enters the submucosa, at the lower far right, courses out of plane to innervate a second villus on a neighboring section.) B: The base of the villus illustrated in panel A. In this illustration the DIC interference has been attenuated in order to give a clearer view of the pattern of division and the continuity of the collaterals of the villus afferent in the submucosal and crypt region of the mucosa. C,D: A villus afferent in the apical tip of a villus illustrating how individual afferent neurites course, without branching or with minimal branching (see bottom of lower power panel D), into the apical pole of a villus where they then ramify extensively to end in plates of varicosities as well as numerous distributed terminals (higher-power panel C). c, crypt. Scale bars = 25 µm in A,B; 10 µm in C; 20 µm in D.