Talk:Musculoskeletal System - Muscle Development Timeline

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Cite this page: Hill, M.A. (2021, May 8) Embryology Musculoskeletal System - Muscle Development Timeline. Retrieved from


Muscle patterning in mouse and human abdominal wall development and omphalocele specimens of humans

Anat Rec (Hoboken). 2012 Dec;295(12):2129-40. doi: 10.1002/ar.22556. Epub 2012 Sep 14.

Nichol PF1, Corliss RF, Yamada S, Shiota K, Saijoh Y.


Human omphalocele is a congenital defect of the abdominal wall in which the secondary abdominal wall structures (muscle and connective tissue) in an area centered around the umbilicus are replaced by a translucent membranous layer of tissue. Histological examination of omphalocele development and moreover the staging of normal human abdominal wall development has never been described. We hypothesized that omphalocele is the result of an arrest in the secondary abdominal wall development and predicted that we would observe delays in myoblast maturation and an arrest in secondary abdominal wall development. To look for evidence in support of our hypothesis, we performed a histological analysis of normal human abdominal wall development and compared this to mouse. We also conducted the first histological analysis of two human specimens with omphalocele. In these two omphalocele specimens, secondary abdominal wall development appears to have undergone an arrest around Carnegie Stage 19. In both specimens disruptions in the unidirectional orientation of myofibers were observed in the external and internal obliques, and rectus abdominis but not in the transversus abdominis. These latter findings support a model of normal abdominal wall development in which positional information instructs the orientation of myoblasts as they organize into individual muscle groups. Copyright © 2012 Wiley Periodicals, Inc.

PMID 22976993

Development of the rectus abdominis and its sheath in the human fetus

Yonsei Med J. 2012 Sep;53(5):1028-35. doi: 10.3349/ymj.2012.53.5.1028.

Yang JD1, Hwang HP, Kim JH, Rodríguez-Vázquez JF, Abe S, Murakami G, Cho BH.


PURPOSE: Although the rectus abdominis and its sheath are well known structures, their development in the human fetus is poorly understood. MATERIALS AND METHODS: We examined rectus abdominis and sheath development in semiserial horizontal sections of 18 fetuses at 5-9 weeks of gestation. RESULTS: Rectus muscle differentiation was found to commence above the umbilicus at 6 weeks and extend inferiorly. Until closure of the anterior chest wall via fusion of the bilateral sternal anlagen (at 7 weeks), the anterior rectal sheath originated from the external oblique and developed towards the medial margin of the rectus abdominis at all levels, including the supracostal part. After formation of the anterior sheath, fascial laminae from the internal oblique and transversus abdominis contributed to formation of the posterior rectus sheath. However, the posterior sheath was absent along the supracostal part of the rectus abdominis, as the transversus muscle fibers reached the sternum or the midline area. Therefore, it appeared that resolution of the physiological umbilical hernia (8-9 weeks) as well as chest wall closure was not required for development of the rectus abdominis and its sheath. Conversely, in the inferior part of the two largest fetal specimens, after resolution of the hernia, the posterior sheath underwent secondary disappearance, possibly due to changes in mechanical stress. CONCLUSION: Upward extension of the rectus abdominis suddenly stopped at the margin of the inferiorly developing pectoralis major without facing the external intercostalis. The rectus thoracis, if present, might correspond to the pectoralis.

PMID 22869489