Physiology was a course taught at Starfleet Academy in the 23rd century.
In 2266, Montgomery Scott, during a fight with Tol people on Neesan, quoted his old physiology professor: "You've got to use your heads, boys!" (TOS comic: "The Cosmic Cavemen")
Julian Bashir spent more than five semesters at Starfleet Medical Academy studying alien physiology. (DS9 novel: The Long Night)
Odo once commented that he knew more about his own physiology than any doctor. (DS9 novel: Warped)