Auricular cartilage configuration: A histological study using late-stage human fetuses and adult cadavers

The auricular cartilage is considered to develop from a funnel-like arrangement of six embryonic hillocks. However, there is little information as to when and how the initial cartilage plate differentiates into the major three hollows or caves: the concha, the scapha and the triangular fossa. We examined semiserial histological sections from 42 human fetuses as well as from seven cadavers of elderly individuals. Tangential sections from adults suggested that three ring-like cartilages were combined to provide a single auricular cartilage and that the external auditory meatus was attached to the lowest ring or concha. All of the fetuses studied carried the three major hollows delineated by skin folds. These skin folds often contained a cartilage loop as a core in place of a thickening or tubercle. Conversely, some of the skin folds corresponded to a highly wavy cartilage plate without looping. According to whether the cartilage loop was present or absent in horizontal sections from 35 fetuses, we classified the cartilage morphology into four patterns, the most frequent of which was absence of the triangular fossa loop (27 fetuses), followed by absence of the scapha loop (11 fetuses). Each pattern was evenly distributed among small and large fetuses. This suggested that some form of cartilage correction or reconstruction was likely to occur after birth, especially at the triangular fossa and/or scapha. Infants appear to show significant region-specific variation in the postnatal growth of the auricular cartilages, especially at the triangular fossa and/or scapha.