Final answer:
The multinucleation of skeletal muscle fibers arises from the fusion of embryonic myoblasts, each contributing a nucleus to the resulting fiber, allowing for increased protein production necessary for muscle activity.
Step-by-step explanation:
The origin of muscle fibers explains why each muscle fiber contains numerous nuclei. During embryonic development, myoblasts, which are muscle precursor cells, each containing a single nucleus, merge to form a muscle fiber. As a result of this fusion, muscle fibers become multinucleated.
Each nucleus contributes its genetic information, allowing the cell to produce significant amounts of proteins and enzymes, which are crucial for muscle function and growth. Unlike skeletal muscle fibers, cardiac and smooth muscle fibers do not become multinucleated because the myoblasts that form these muscle cells do not fuse together in the same way.