It is absolutely required to take anatomy in high school if I want to get into an occupational therapy program in college?

no

neither is physics

Occupational Therapy is a Masters degree anyway

so you have to have a bachelors in something else first before you can even apply

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http://www.aota.org/Education-Careers/Considering-...

3. What should I major in at the undergraduate level if I apply to an entry-level master's or an entry-level doctoral program?

Examples of what other students have majored in at the undergraduate level include biology, kinesiology, psychology, sociology, anthropology, liberal arts, and anatomy. It is important that you contact the educational programs to which you are interested in applying and make sure you have taken the necessary prerequisites for admission into their programs.

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you might find a combined BS/MS program like this

http://ot.keuka.edu/bachelor-of-science/

but notice is says

"This degree doesn’t provide you with the eligibility needed for certification or licensure in occupational therapy, but it is the first step."

you STILL have to complete the Masters degree to become eligible to be licensed

http://www.otcareerpath.com/occupational-therapist...

edit: doesn't change my answer

find your school in the link I provide in the comment below

or tell us the names of the schools you're looking into

the WHOLE point of a 5 year program is to get a Masters degree

just like the combined program I linked above, which says

"The B.S. in occupational science is awarded after four years of study in the five-year B.S./M.S. program in occupational science/occupational therapy."

so, no

you will NOT be able to take the exam after you get your bachelors

you will need to continue on and get your Masters in the 5th year

OT is a Masters program

It doesn't matter what you take in high school. Only your choice of college classes matter, and even then there are options.