Answer:
Soon after conception, the embryo differentiates into three layers of cells. The mesoderm, or middle layer, will develop into your baby's bones – as well as her heart muscles, kidneys and sex organs. The inner layer (called the endoderm) becomes your baby's digestive system, liver and lungs.
The skeletal system is composed of cartilage and bone and functions as a structural framework for the body, facilitating movement and protecting internal organs. ... During fetal development, long bones form through the process of endochondral ossification, and flat bones develop by intramembranous ossification.