The epidermis and the plasma membrane are distinct structures with different functions and locations. The plasma membrane is a cell's outer boundary, while the epidermis is a tissue's outer layer.
Plasma Membrane: The Cell's Protective Barrier
The plasma membrane, also known as the cell membrane, is the outermost layer of individual cells. It's a thin, selectively permeable membrane that separates the cell's interior from its external environment. Its primary function is to regulate what enters and exits the cell, protecting the cell's contents and maintaining its internal environment. The plasma membrane is found in all living cells. This is supported by the provided text which states that the plasma membrane is present in all living organisms and keeps the interiors and external environments of the cell separate. Examples of research focusing on the plasma membrane include studies on its proteomic characterization in human epidermis ( https://pubmed.ncbi.nlm.nih.gov/15373774/) and its role in maintaining cell size in the periderm ( https://journals.plos.org/plosgenetics/article?id=10.1371/journal.pgen.1004614).
Epidermis: The Outermost Layer of a Multicellular Organism
The epidermis, on the other hand, is the outermost layer of cells in many multicellular organisms. In plants, it covers the stems, leaves, roots, and flowers. In animals, like humans, the epidermis is the outer layer of the skin. The epidermis is composed of many cells, each with its own plasma membrane. The provided text explicitly states that the epidermis is the outermost layer of cells that cover various plant parts. Examples of research involving the epidermis include studies on its role in wound healing ( https://www.sciencedirect.com/science/article/pii/S1534580722004130), autophagy in larval epidermis ( https://pmc.ncbi.nlm.nih.gov/articles/PMC9194749/), and pH regulation in root epidermis ( https://www.pnas.org/doi/abs/10.1073/pnas.1721769115).
In short: the plasma membrane is a single layer surrounding a cell, while the epidermis is a tissue composed of many cells.
