Final answer:
Myoblasts proliferate and fuse to form a myotube, which later matures into a multinucleate skeletal muscle cell. Myoblasts come from the mesoderm and upon fusing, contribute their nuclei to the developing muscle fiber.
Step-by-step explanation:
Myoblasts proliferate and eventually fuse to form a myotube, which is essentially a developing muscle fiber. This is a critical process in the formation of skeletal muscle tissue. As myoblasts are muscle-forming stem cells derived from the mesoderm, they migrate to various regions in the body where they fuse together to form this myotube. This syncytium, or myotube, is characterized by many nuclei contained within a continuous cytoplasm, resulting in the multinucleate nature of mature skeletal muscle cells. Each nucleus originates from one of the contributing myoblasts that have fused together, and unlike cardiac or smooth muscle cells, these myoblasts do not fuse, which is why they are not multinucleate.
Skeletal muscle tissue develops from multiple myoblasts that are surrounded by connective tissue and reveal a striated appearance under the microscope due to the alignments of actin and myosin proteins. This arrangement allows skeletal muscles to contract and generate force. The development of muscle fibers through myotube formation is an example of how specific cell types arise from the embryonic mesoderm and differentiate to perform specialized functions in the body.