During embryo development which of the following germ layers differentiates to form the muscles?
The three primary germ layers of the embryo include: the ectoderm, endoderm, and mesoderm. The introderm is not an actual term in biology. The endoderm forms the gastrointestinal tract, the lungs, the pharynx and parts of the urinary system. The ectoderm forms the skin (or epidermis) and related structures like hair and nails, as well as the brain and spinal cord. It is the mesoderm that differentiates during embryonic development to form connective tissues like cartilage, bone, and muscle.[Life Science]