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Morphogenesis of the human gluteus maximus muscle arising from two muscle primordia
Insights
A newly identified coccygeofemoralis muscle in human embryos fuses with the gluteus maximus. This finding reveals that adult muscles can develop from the fusion of multiple fetal muscles during development.
Area of Science:
- Anatomy
- Embryology
- Morphogenesis
Background:
- The gluteus maximus is a primary muscle of the buttocks.
- Understanding the developmental origins of skeletal muscles is crucial in human anatomy.
Purpose of the Study:
- To describe a supernumerary muscle found in human embryos and fetuses.
- To investigate the developmental relationship between this new muscle and the gluteus maximus.
- To propose a name and understand the embryological origin of the coccygeofemoralis muscle.
Main Methods:
- Embryological examination of human fetuses.
- Observation of muscle development and fusion during the prenatal period.
- Anatomical analysis of muscle origins and insertions.
Main Results:
- A supernumerary muscle, named coccygeofemoralis, was identified on the distal margin of the gluteus maximus in human embryos and fetuses.
- Initially separate, the coccygeofemoralis muscle fuses with the gluteus maximus during prenatal development.
- Postnatally, the coccygeofemoralis is incorporated into the gluteus maximus, forming its pars coccygea.
Conclusions:
- The coccygeofemoralis muscle represents a distinct fetal muscle that fuses with the gluteus maximus.
- The gluteus maximus in adults is composed of the fetal gluteus maximus (pars sacroiliaca) and the fetal coccygeofemoralis (pars coccygea).
- This study demonstrates that adult muscles can arise from the fusion of multiple fetal muscular components, offering insights into muscle morphogenesis.
Abstract:
In human embryos and fetuses a supernumerary muscle was found situated on the distal margin of the gluteus maximus muscle and supplied by the most distal main branch of the inferior gluteus nerve. According to its origin and insertion it is being named the coccygeofemoralis muscle. In embryos and fetuses of up to 40 mm in CR length the coccygeofemoralis muscle is separated by loose connective tissue from neighbouring fetal muscles. Later on, close contact between the coccygeofemoralis and the distal margin of the fetal gluteus maximus muscle develops, and during the prenatal period both fetal muscles gradually fuse. Postnatally, the coccygeofemoralis muscle is incorporated into the gluteus maximus muscle of which the pars sacroiliaca corresponds to the fetal gluteus maximus itself and the pars coccygea represents the fetal coccygeofemoralis muscle. With respect to the general process of muscle morphogenesis, the developmental pattern described for the gluteus maximus muscle demonstrates that adult muscles may be formed by a fusion of several fetal muscles.