- 比較解剖学的研究で哺乳類の気管支樹の基本モデルとして提案されている左右の気管支の対称性が、ヒトの胎児の気管支樹に当てはまるかどうかを検討
- ヒト成人の気管支分岐構造の原型が胎児期に形成され、維持されることを実証
- すべての肺葉気管支、B6、B8、B9、および B10 の亜分節気管支の形態および分岐位置は、遺伝的に決定される可能性がある
- B10 の亜分節気管支以降の末梢枝では個々の胚間に共通の構造は見つからず、この領域での枝形成は遺伝的要因よりも環境的要因により影響されることが示唆された
Fujii S, Muranaka T, Matsubayashi J, Yamada S, Yoneyama A, Takakuwa T. Bronchial tree of the human embryo: Examination based on a mammalian model. J Anatomy 2024, 244, 159-169 http://doi.org/10.1111/joa.13946 .
The symmetry of right and left bronchi, proposed in a previous comparative anatomical study as the basic model of the mammalian bronchial tree, was examined to determine if it applied to the embryonic human bronchial tree. Imaging data of 41 human embryo specimens at Carnegie stage (CS) 16–23 (equivalent to 6–8 weeks after fertilization) belonging to the Kyoto collection were obtained using phase-contrast X-ray computed tomography. Three-dimensional bronchial trees were then reconstructed from these images. Bronchi branching from both main bronchi were labeled as dorsal, ventral, medial, or lateral systems based on the branching position with numbering starting cranially. The length from the tracheal bifurcation to the branching point of the labeled bronchus was measured, and the right-to-left ratio of the same labeled bronchus in both lungs was calculated. In both lungs, the human embryonic bronchial tree showed symmetry with an alternating pattern of dorsal and lateral systems up to segmental bronchus B9 as the basic shape, with a more peripheral variation. This pattern is similar to that described in adult human lungs. Bronchial length increased with the CS in all labeled bronchi, whereas the right-to-left ratio was constant at approximately 1.0. The data demonstrated that the prototype of the human adult bronchial branching structure is formed and maintained in the embryonic stage. The morphology and branching position of all lobar bronchi and B6, B8, B9, and the subsegmental bronchus of B10 may be genetically determined. On the other hand, no common structures between individual embryos were found in the peripheral branches after the subsegmental bronchus of B10, suggesting that branch formation in this region is influenced more by environmental factors than genetic factors.