Final answer:
A retractor is a surgical instrument used to hold open layers of tissue during procedures. The University of Michigan WebScope enables detailed observation of histological samples, such as the stratified layers of cells in the epidermis.
Step-by-step explanation:
The instrument used to hold open layers of tissue, exposing the areas beneath, is known as a retractor. In surgical procedures, retractors are essential tools that surgeons use. They come in different shapes and sizes, designed to hold back different types of tissues such as skin, fat, or muscles, thereby giving surgeons a clear view and access to the underlying organs.
When observing tissue samples, such as the ones provided by the University of Michigan WebScope, using histology slides, one might notice different cell types based on the specific tissue being observed. For skin tissue, zooming in on the cells at the outermost layer, one may notice that the cells are flat and stratified as they make up the epidermis, part of which includes dead cells at its surface arranged in layers to form a protective barrier.