Which of the following functions is NOT associated with the mesoderm?

The mesoderm is one of the three primary germ layers in early embryonic development, and it plays a critical role in forming various organ systems in the body. Among its functions, the mesoderm is responsible for the development of the excretory system, the gonads, and various forms of connective tissues, which are all vital supportive structures within the body.

On the other hand, the nervous system, which includes the brain, spinal cord, and peripheral nerves, is primarily derived from the ectoderm, not the mesoderm. The ectoderm is specifically responsible for forming structures related to the nervous system, as well as the skin and related structures. Therefore, the function of forming the nervous system is not associated with the mesoderm, making it the correct answer in this context. Understanding germ layer differentiation is crucial in developmental biology, as it highlights the specialized roles each layer plays in the organism's development.