What is the study of the functions of the organs and systems called?

The study of the functions of the organs and systems is called physiology. This branch of biological science focuses on understanding how various biological systems and organs operate, including how they interact and work together to maintain homeostasis and overall health. It encompasses processes such as circulation, respiration, digestion, and the functioning of the nervous system.

Histology, on the other hand, is the study of the microscopic structure of tissues, while anatomy examines the physical structures and organization of organisms. Cytology focuses on the study of cells, including their structure and function. Each of these fields contributes to the broader understanding of biology, but physiology specifically addresses the functional aspects, making it the correct answer in this context.