Spatial relationship between the vesicles of upper inner segment and CC lumen. (A) Enlarged views of Figure 12 (panel 4) showing both the block face x-y view (top panel) and orthogonal x-z view (bottom panel). The close spatial relationship between a vesicle (white arrow) and a membrane organelle in the upper IS is particularly prominent in the orthogonal view. (B) Top panel shows the same block face image of (A); a white arrow points to a CC luminal vesicle that appears to be localized in the outer shaft based on the orthogonal view (bottom panel). Two black arrows label two out of several other CC luminal vesicles, which can be readily distinguished from the dark labeling of the ciliary PM and CP space.