Where do they find the live human models used in those graphic, explicit medical and sex ed films and textbooks?

Where do they find these people? What's the recruiting, screening, and hiring process for people willing to do this kind of work?

What about the people shown in those graphic sex ed textbooks and films used in college Human Sexuality classes? Just who are they? Are they real couples who don't mind having sex on camera for educational purposes? Professional models who don't mind doing sex stuff on behalf of academia?

How does that whole thing work?

I would suppose in much the same manner in which people work in making porn photos or videos.

There truly are people who are not shy about such things and who appreciate making a bit of extra income. There might be a flyer on an academic billboard (or online nowadays) or by word of mouth or medical personnel mentioning it to patients they think might be willing. And then once some are signed up, word of mouth might be enough for others to volunteer.

Since Internet exists we have realized that there are millions of people who are exhibitionists and who do not hesitate to show themselves naked or having sex, so why not do it with a clear conscience since it is for education and not for fun?

I would suppose in much the same manner in which people work in making porn photos or videos.

There truly are people who are not shy about such things and who appreciate making a bit of extra income. There might be a flyer on an academic billboard (or online nowadays) or by word of mouth or medical personnel mentioning it to patients they think might be willing. And then once some are signed up, word of mouth might be enough for others to volunteer.

When I did nude art modeling back in my early 30s, all my assignments came from word of mouth, on the recommendation of an older, long-established model who vouched for my character. I would have LOVED to have stuck with it, see I far I could go. Unfortunately, with a full time job AND me being the only child of aging parents, an abundance of free time wasn't exactly a luxury that I had.