Cho, Kwang HoJin, Zhe WuUmeki, ShinichiYamamoto, MasahitoMurakami, GenAbe, ShinichiRodríguez Vázquez, José Francisco2024-10-222024-10-222021-08-21Cho KH, Jin ZW, Umeki S, Yamamoto M, Murakami G, Abe SI, Rodríguez-Vázquez JF. Human orbital muscle in adult cadavers and near-term fetuses: its bony attachments and individual variation identified by immunohistochemistry. Surg Radiol Anat. 2021 Nov;43(11):1813-1821. doi: 10.1007/s00276-021-02819-10930-103810.1007/s00276-021-02819-1https://hdl.handle.net/20.500.14352/109206Purpose: To compare fetal and adult morphologies of the orbital muscle (OM) and to describe the detailed topographical anatomy in adults. Methods: Using unilateral orbits from 15 near-term fetuses and 21 elderly cadavers, semiserial horizontal or sagittal paraffin sections were prepared at intervals of 20-100 µm. In addition to routine histology, we performed immunohistochemistry for smooth muscle actin. Results: At near term, the OM consistently extended widely from the zygomatic bone or the greater wing of the sphenoid to the maxilla or ethmoid. Thus, it was a large sheet covering the future inferior orbital fissure. In contrast, the adult OM was a thin and small muscle bundle connecting (1) the greater wing of the sphenoid to the maxilla (11/19 cadavers), (2) the lesser wing of the sphenoid to the maxilla (5/19) or the greater wing (3/19). The small OM was likely to be restricted within the greater wing (5/19 cadavers) or the maxilla (3/19). Two of these five types of OM coexisted in eight orbits. OM attachment to the lesser wing was not seen in fetuses, whereas ethmoid attachment was absent in adults. Conclusions: The lesser wing attachment of the OM seemed to establish after birth. A growing common origin of the three recti was likely involved in "stealing" the near-term OM attachment from the ethmoid. The strong immunoreactivity of remnant-like OM in the elderly suggests that OM contraction is still likely to occur against the increased flow through a thin vein. However, the contraction might have no clinical significance.engjournal article1279-8517https://doi.org/10.1007/s00276-021-02819-134417852https://link.springer.com/article/10.1007/s00276-021-02819-1restricted access611Adult cadaverHuman fetusInferior orbital fissureOrbital muscleSmooth muscleCiencias BiomédicasAnatomía2410.02 Anatomía Humana