The science that studies the functions of the body, individual cells, organs and their systems is called?

This science is called physiology.
Physiology is a science that studies the regularity of the vital functions of an organism, about its cells and its organs.

One of the components of a person's success in our time is receiving modern high-quality education, mastering the knowledge, skills and abilities necessary for life in society. A person today needs to study almost all his life, mastering everything new and new, acquiring the necessary professional qualities.