Final answer:
The epithelial system is comprised of epithelial tissues and cells that cover external and internal surfaces, form glandular tissues, and create specialized membranes. These components perform various functions, including protection, secretion, and permeability, and originate from embryonic layers like the ectoderm, endoderm, and mesoderm.
Step-by-step explanation:
The components that are part of the epithelial system include large sheets of cells forming epithelial tissues, which cover all surfaces of the body exposed to the outside world and line the outside of organs. These epithelia not only make up the skin but also line internal pathways such as the airways, digestive, urinary, and reproductive systems. Moreover, epithelial tissues contribute significantly to the formation of glandular tissue within the body. The epithelial membranes, like the skin and mucous membranes, are made up of epithelium attached to a layer of connective tissue. They line body cavities and passageways that open to the external environment, and they are covered by mucus secreted by epithelial exocrine glands. Epithelial cells, highly specialized depending on their location and function, are capable of secretion and are responsible for a range of functions including absorption, protection, and selective permeability. Certain epithelial cells are derived from each of the major embryonic layers and contribute to the form and function of structures like the endothelium and mesothelium.