Figure 7. Quantitative comparison of the connexon density between the loosely-packed gap junctions in the outer cortex and the crystalline-packed ones in the inner cortex. The number of connexons in the typical crystalline-packed GJs is approximately 2 times higher than that of the loosely-packed GJs. The connexons from fifteen representative gap junctions of each type from three replicas were counted. This result suggests that although the percentage of membrane area specialized as gap junctions is reduced approximately 5 times from the outer cortex to inner cortex (Figure 6), the number of connexons is reduced only about 2.5 times in the deeper cortical region during fiber cell maturation.