How is the self-maintenance of the “organism” biosystem carried out?

Any organism has a complex structure. The body consists of many organ systems, dozens of types of tissues. To maintain such complex systems, there are many ways to protect. In the event of damage to cells or tissues, regeneration begins. Some cells protect the body from viruses and bacilli. Some systems are involved in cleaning the body of harmful substances. The larger the organism, the more complex it is. Accordingly, it will be easier to disrupt its work, but it will be more difficult to destroy it because of the protection systems.