Use Retin-A exactly as your doctor has prescribed it for you. Follow all directions on your prescription label. Do not use this medicine in larger or smaller amounts or for longer than recommended. Do not take by mouth. Retin-A is for use only on the skin.
Definition of wall for English Language Learners : a structure of brick, stone, etc., that surrounds an area or separates one area from another : the structure that forms the side of a room or building
A cell wall is a structural layer that surrounds most types of cells, situated outside the cell membrane. It can be tough, flexible, and sometimes rigid. It provides the cell with both structural support and protection, and also acts as a filtering mechanism. Cell walls are present in most prokaryotes, and in plants, fungi and other eukaryotes, where a major function is to act as pressure vessels, preventing over-expansion of the cell when water enters. Cell walls are absent from Mycoplasma bacteria, animal, and human cells.