Fetal development of external nose cartilages.

Abstract

There seems to be no information on when and how the nasal capsule cartilage is divided into the lateral nasal cartilage (LNC) and greater alar cartilage (GAC). Likewise, there is no information of timing and sequence of development of the medial crus of GAC. We examined histological sections from 22 human fetuses with 45-350 mm of crown-rump length (approximately 9-40 weeks of gestational age). The LNC and GAC were separated from the antero-inferior marginal part of the nasal capsule cartilage at 10-12 weeks. The initial sesamoid was a wavy bar and it did not accompany a joint cavity. The LNC did not make an end-to-end attachment to the septal cartilage and these cartilages were separated by sesamoid cartilages in levels below the nasal bone. However, we did not find a sesamoid between the LNC and GAC. After 27 weeks, the medial crus of the GAC was seen in the antero-inferior side of the septal cartilage. Thus, independently from the septal cartilage, it seemed to develop secondarily from the GAC main part. Relative to the nasal bone, the LNC at late-term was small in the supero-inferior axis. The vomeronasal cartilage was distant from and located in the posterior side of the external nasal cartilages and vestibulum. At birth, the LNC as well as the GAC including its medial crus seemed to be still separated from the septal cartilage. Their connections most likely establish postnatally with tight interdigitation of highly flexed cartilage ends. No lesser alar cartilage appeared at late-term.