Not only is Khan Academy noted for providing academic assistance in core studies, it offers short and interesting videos on topical health issues as well as visual explanations of the anatomy of the human body.
Project Alert - Videos
These videos supplement your lessons with students playing different roles in real life scenarios dealing with the dangers of bad health choices and how to make good decisions.
AsapSCIENCE
A site of YouTube Videos illustrating the human body. These videos are age appropriate and interesting for teens.
Ted-Ed - Getting Under Our Skin
This site provides videos that capture the attention of teens through animation. There are several on the human body and diseases that affect it.
The website is currently under construction but their YouTube channel has various health videos and games for elementary grades on nutrition, cleanliness and pollution around us.