Epithelium is a tissue type in the human body that covers surfaces, lines cavities, and forms glands. It is one of the four main types of tissues, accompanied by connective, muscle, and nervous tissues.
This tissue is primarily composed of closely packed cells that are tightly joined together. Its main function is to act as a protective barrier, preventing the underlying tissues and organs from damage, injury, and dehydration. Epithelium also assists in regulating the exchange of substances between different body compartments, such as the absorption of nutrients in the intestines or the removal of waste products through the kidneys.
Epithelial cells are characterized by their distinct shape and arrangement. Depending on the location, they can be classified into different types, including simple, stratified, pseudostratified, columnar, cuboidal, and squamous epithelium. Simple epithelium consists of a single layer of cells, while stratified epithelium has multiple layers. Pseudostratified epithelium appears stratified but consists of only one layer of cells. Columnar epithelium contains long, rectangular cells, cuboidal epithelium has cube-shaped cells, and squamous epithelium consists of flat, scale-like cells.
Epithelial tissues are found throughout the human body, covering the skin, lining the respiratory and digestive tracts, forming the urinary and reproductive systems, and composing various glands. Their structure and function can vary depending on the specific location, allowing epithelial tissues to fulfill diverse roles in protecting, absorbing, secreting, and transporting substances in the body.
