Two slices of real-proportion skin, a microscope with an eyepiece scale, and six places on the body to compare. Find each layer, measure it, see how deep an injury has to go to bleed, then go inside the epidermis and the dermis.
Follow-along slideshow · 22 slides that walk through the worksheet, question by question
Printable student worksheet (PDF) · two pages, Day 1 on the front, Day 2 on the back
Low-write worksheet (PDF) · same questions with tick boxes, word banks and worked examples
Teacher guide: NYSSLS, SEP and CCC alignment (PDF)
This is a model, so every run gives the same numbers. The slides are drawn, not photographed, with layer thicknesses set to rounded typical adult values from published measurements (epidermis from about 0.05 mm on the eyelid to about 1 mm on the heel; dermis from about 0.4 mm on the eyelid to about 3 mm on the back). Real people vary by a quarter or more with age, sex and wear. The eyepiece scale is simplified to 50 divisions. The four-week cell journey is a typical thin-skin time; published estimates run from about four to eight weeks, and the trip slows with age. Pull-test forces are model values for a strip 10 mm wide and 0.5 mm thick, chosen to match the tissues' structure, not measurements of these layers. Anatomy & Physiology, Hole's Essentials 6.2: Layers of the Skin.