Department of Anatomy, Tokyo Dental College, Tokyo, Japan.
Division of Basic Medical Science, Tokai University School of Medicine, Isehara-shi, Japan.
Anat Rec (Hoboken). 2024 Nov;307(11):3574-3581. doi: 10.1002/ar.25507. Epub 2024 May 24.
The temporomandibular joint (TMJ) is a complex structure that plays a vital role in the movement of the jaw. Some anatomy and dental textbooks show that, at the medial margin, the TMJ capsule attaches to a suture between the sphenoid ala major and the temporal bone squamosa. In near-term fetuses, the ala major extends posterolaterally to approach the TMJ. In this study, we aimed to investigate the contribution of the sphenoid ala major to the socket of the TMJ in near-term fetuses. We examined histological sections from 22 human fetuses (approximately 15-40 weeks). At midterm, the lateral and superior walls of the TMJ cavity were formed by the temporal bone squamosa, whereas the ala major was distant from the joint. However, at near-term, the ala major formed the medial wall of almost the entire part of the joint cavity. The top of the TMJ was attached to both the squamosa and ala major, with the condylar head consistently separated from the sphenoid by the joint disk. We observed a significant descent of the middle cranial fossa in near-term fetuses, which brought the ala major close to the TMJ. This transient position of the TMJ near the sphenoid is likely due to brain enlargement and posterolateral growth of the ala major. After birth, occlusion causes the anterior growth of the mandibular fossa of the squamosa, which moves the ala major away from the TMJ. Similarly, the lateral growth of the sphenoid toward the squamosa suture may also stop in children.
颞下颌关节(TMJ)是一个复杂的结构,在下巴的运动中起着至关重要的作用。一些解剖学和牙科教科书显示,在关节内侧缘,TMJ 囊附着在蝶骨大翼和颞骨鳞部之间的一条缝线上。在近胎龄胎儿中,大翼向外侧后延伸以接近 TMJ。在这项研究中,我们旨在研究蝶骨大翼对近胎龄胎儿 TMJ 窝的贡献。我们检查了 22 个人类胎儿(约 15-40 周)的组织学切片。在中期,TMJ 腔的外侧壁和上壁由颞骨鳞部形成,而大翼远离关节。然而,在近胎龄时,大翼形成了几乎整个关节腔的内侧壁。TMJ 的顶部附着在鳞部和大翼上,髁突头始终与蝶骨由关节盘隔开。我们观察到近胎龄胎儿中颅中窝明显下降,使大翼靠近 TMJ。TMJ 靠近蝶骨的这种短暂位置可能是由于大脑增大和大翼向外侧后生长所致。出生后,咬合导致鳞部下颌窝的前向生长,使大翼远离 TMJ。同样,蝶骨向鳞部缝的外侧生长也可能在儿童期停止。