Curriculum Module
Axial Skeleton Development
The axial skeleton forms the skull, vertebral column, ribs, and sternum. It develops from paraxial mesoderm (somites), lateral plate mesoderm, and neural crest cells through both intramembranous and endochondral ossification.
Somites & Mesenchyme
Paraxial Mesoderm forms a segmented series of somitomeres in the head and Somites in the occipital region downward. By late week 4, somites differentiate into Sclerotome and dermomyotome.
Sclerotome cells become highly proliferative, forming loosely organized embryonic connective tissue called Mesenchyme. Most bones initially appear as hyaline cartilage models, which harden later through Endochondral Ossification. Neural Crest Cells also contribute massively to the face.
Key Insight
This stage is critical for the formation of embryonic support structures, establishing the main body axis.