This study investigates the development of the primary and secondary jaw joints in humans, focusing on their concomitance and subsequent disconnection. Development begins with the primary temporomandibular joint as a connection between Meckel's cartilage and the incus, while the secondary temporomandibular joint develops anteriorly as an articulation between the mandibular condyle and the mandibular fossa. Previous research in mice has provided insights into the morphogenesis of these joints, but their specific development of the 3D morphogenesis in humans remains unclear. To address this gap, histological serial sections of embryos and fetuses ranging from 19 to 230 mm crown-rump length were analyzed. The 3D morphogenesis of the middle ear and the temporomandibular joint was examined, paying attention to the morphological characteristics, timing, and potential mechanisms of movement and disconnection. The primary jaw joint is initially formed at 25 mm (8th week), followed by the appearance of the secondary jaw joint arising at 87 mm (12th week). Both joints persist present simultaneously, until a separation occurs between 150 and 230 mm (18th-24th week). It is remarkable that both joints remain concomitant and function somehow for a period exceeding 6 weeks, with the mechanism of their separation still unclear. Understanding the precise timing and functional movements involved with these temporarily connected joints is crucial for comprehending the overall development of the temporomandibular joint. Further research is needed to explore the molecular and cellular processes underlying these developmental changes.

这项研究调查了人类初级和次级颌关节的发育，重点关注它们的共生和随后的分离。发育从初级颞下颌关节开始，作为梅克尔软骨和砧骨之间的连接，而次级颞下颌关节向前发育，作为下颌髁和下颌窝之间的关节。先前对小鼠的研究已经深入了解这些关节的形态发生，但它们在人类中的 3D 形态发生的具体发展仍不清楚。为了解决这一差距，对冠臀长度范围为 19 至 230 毫米的胚胎和胎儿的组织学连续切片进行了分析。检查中耳和颞下颌关节的 3D 形态发生，关注运动和断开的形态特征、时间和潜在机制。主颌关节最初在 25 毫米（第 8 周）处形成，随后在 87 毫米（第 12 周）处出现次颌关节。两个关节持续同时存在，直到分离发生在 150 至 230 毫米之间（第 18 至 24 周）。值得注意的是，两个关节在超过 6 周的时间内仍然保持并存并以某种方式发挥作用，但它们分离的机制仍不清楚。了解这些临时连接的关节所涉及的精确时间和功能运动对于理解颞下颌关节的整体发育至关重要。需要进一步的研究来探索这些发育变化背后的分子和细胞过程。