Search the website of the school you're considering. Usually, an accredited school states that fact right up front, because it makes sense to draw attention to a selling point. If you can't easily find information about accreditation, it's a warning flag. Another warning flag is any statement on the school website to the effect that a school program can be wonderful without accreditation, or that accreditation is overrated.
Check to see whether the online school is accredited by an official accrediting agency. You can do this quickly and easily by going to the U.S. Department of Education website and searching its database of accredited post-secondary institutions and programs. Although the DOE is not an accrediting agency, it maintains a list of accrediting agencies and accrediting schools. You can type in the name of the online school you're considering to see whether it's accredited.
If you can positively verify that the online school is accredited, search its website for information about online courses or degrees. It's important to find out whether what you want can be earned entirely online, or whether you must also attend onsite classes part time. Many schools offer classes that are mostly online, with a few mandatory seminars at the school.
Verify that the school offers anatomy and physiology coursework or degrees. Just because a school offers some coursework, or some degrees online, it doesn't automatically follow that they'll have what you want. Look for tabs or menu items reading "Academics" or "Online" for a listing of degrees.
Look for the "Registration" tab. Some schools make it possible to apply electronically.