The Meckel’s cartilage in human embryonic and early fetal periods

Abstract

The Meckel's cartilage itself and the mandible are derived from the first branchial arch, and their development depends upon the contribution of the cranial neural crest cells. The prenatal development of the Meckel's cartilage, along with its relationship to the developing mandible and the related structures, were studied histologically in human embryos and fetuses. The material was obtained from a collection of the Department of Anatomy, and laboratory procedures were used to prepare sections, which were stained according to standard light-microscopy methods. The formation of the Meckel's cartilage and its related structures was observed and documented. Some critical moments in the development of the Meckel's cartilage are suggested. The sequential development of the Meckel's cartilage started as early as stage 13 (32 days) with the appearance of condensation of mesenchymal cells within the mandibular prominence. During stage 17 (41 days), the primary ossification center of the mandible appeared on the inferior margin of the Meckel's cartilage. The muscular attachments to the Meckel's cartilage in embryos were observed at stage 18 (44 days). Their subsequent movement into the developing mandible during the 10th week seemed to diminish the role of the Meckel's cartilage as the supportive core; simultaneously, the process of regression within the cartilage was induced. During the embryonic period, the bilateral Meckel's cartilages were in closest contact at the posterior surface of their superior margins, preceding formation of the symphyseal cartilage at this site. The event sequence in the development of the Meckel's cartilage is finally discussed.

Trisomy 21 and facial developmental instability

“…Deficiencies in bone formation have been found in DS mouse models, such as lower bone mineral density for trabecular and cortical bone and lower bone volume fraction and fewer rod-like trabeculae (Blazek et al, 2010; Parsons et al, 2007), which suggests that gene-dosage imbalance results in reduced osteoblast and odontoblast activity and ultimately contributes to the unique facial morphology found in DS. Additionally, Meckel's cartilage forms from neural crest cells derived from the first pharyngeal arch and acts as a template around which membrane bone is laid down to form the mandible (Wyganowska-Świątkowska and Przystańska, 2011). It is possible that gene-dosage imbalance impairs morphogenesis of Meckel's cartilage, possibly by impairing the spatiotemporal migration of neural crest cells and disrupting conversion of cartilage to bone;…”

Evolution of the mammalian middle ear and jaw: adaptations and novel structures

“…In humans, Meckel’s cartilage acts as an initial attachment site for the muscles of the mandible. Once these muscles lose contact with Meckel’s and reach the developing dentary, transformation of Meckel’s cartilage commences (Wyganowska‐Swiatkowska & Przystanska, 2011). Loss of muscle attachment to Meckel’s may therefore be a possible stimulus for a change of fate for Meckel’s cartilage.…”

Developmental and genetic perspectives on Pierre Robin sequence

“…A). In humans, Meckel's cartilage primordia is first detected around the 32nd day of gestation at CS13 (4–6 mm, >30 somites) and by CS15 (7–9 mm, 36 days) is histologically identifiable as cartilage [Wyganowska‐Świątkowska, Marzena and Przystańska, ]. The interdependency of components of the craniofacial complex for normal development makes it difficult to definitively identify the contribution of individual elements.…”