When you first log into the website you will have to choose a subscription plan. There are three plans, but I choose the free one (we know teachers want everything for free). Of course the free version is as robust, but the features you can't find for free here can be found for free on other websites.
There is a slider on left side that allows your to move through the layers of the viewer. The first layer that you encounter is the skin. Following that you reach muscles, bones, tendon/ligaments, interior organs, circulatory system, nervous system and finally the brain.
You also have the option to turn on and off individual systems. If you click on the bottom of the slider images, the slider will change from and up and down continuous slider to a left to right slider for each system. This way you can turn on and off specific systems.
On top of the slider column is a box that will allow you to change the model from a male to a female.
Lastly, at the very top there are arrows to move the body up and down and spin it left and right. Although you don't have to use those arrows because you can click and drag the image around. Below that are plus and minus signs that allow you to zoom in and out on the image. You can also do that by scrolling up and down over the image.
Below is a video that will show you the features of this website, but it does show many of the features that are paid features. My suggestion, and this is usually my suggestion for all new sites you are exploring, is to just go to the website and play around with it. :-)
What are some other images or animations you use with your students when discussing the body systems?