Patterning of the vertebrate embryo occurs with respect to three body axes.
Prior to the left-right axis (L–R axis), the anterio-posterior axis (A–P axis) and dorso-ventral axis (D–V axis) are formed. These two body axes automatically define the left and the right side of the embryo that initially shows bilateral symmetry.
Starting from an embryo with two body axes and bilateral symmetry, the development of morphological Left–Right asymmetry can be divided into three phases:
1. Breaking of global embryonic bilateral symmetry and stabilizing this information in an organizing center.
2. left–right information is propagated and transmitted to more outlying tissue and a cascade of asymmetric gene expression is triggered.
3. Recognition of the left–right information by organ primordia and the translation into asymmetric organ morphology.
Pathology
situs anomalies (heterotaxy)
References
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