The Usborne Complete Book of the Human Body is a gorgeous 110-page book that should be great for students in about grades four through eight. Like most Usborne books, it is heavily illustrated with photos, diagrams, and other images.
It covers the systems of the human body by presenting the information under topics and subtopics, with each subtopic given a two-page spread. For example, the circulatory system is covered in three two-page spreads on the heart, circulation, and blood. The reproductive system is covered within a topical section titled Body Changes that has two-page spreads on conception and birth, growing up, hormones, and growing old. (It describes the reproductive act very succinctly and without illustrations.)
While the book primarily teaches about the organs and systems and how they function, it sometimes also has information related to health, nutrition, physical activity, medical care, and other topics. Twelve pages of the book comprise a section titled Health and Medicine. This section covers health, sickness, diseases, the immune system, medical drugs and treatments, and operations, with a brief paragraph each on acupuncture and homeopathy.
There are a few visual activities such as optical illusions and an image used to test for color blindness, but this is an information book rather than an activity book. This printed book has many mentions of internet links to websites with videos, information, and, occasionally, activities. Students get to the internet sites through a dedicated page managed by Usborne.
You might consider using this book alongside an activities book such as Blood and Guts to provide hands-on learning experiences.