Integumentary system is usually included in anatomy textbooks if you want to go into detail.
They are talking about different kind of receptors in the skin, what kind of epithelial cells there are (simple squamous, simple cuboidal, columnar, stratified, etc..) I would look at different kinds of surfaces like tongue surface vs. head surface. And you are set for the integuments.
You can read cliffs AP bio for it but I highly don't recommend using Cliffs for the physiology and anatomy portion of the bio section cuz they really don't go into that much detail.