Growth factors and cytotoxic factors also regulate inflammatory response. These cytokines and other chemicals recruit immune cells to the site of infection and promote healing of damaged tissue following the removal of pathogens. NFkB plays a key role in regulating the immune response to infection.
Stomata facilitate the exchange of gases in the leaf. Carbon dioxide (CO 2 ) diffuses into the leaf through the stomata for use in photosynthesis, and oxygen (O 2 ), the waste product of photosynthesis, diffuses out of the leaf through stomata. Stomata are also crucial for water transport through the xylem .
Humansâand other complex multicellular organismsâhave systems of organs that work together, carrying out processes that keep us alive. The body has levels of organization that build on each other. Cells make up tissues, tissues make up organs, and organs make up organ systems. The function of an organ system depends on the integrated activity of its organs. For instance, digestive system organs cooperate to process food.