What is the function of the stratified columnar epithelium?
Stratified columnar epithelium is a rare type of epithelial tissue composed of column shaped cells arranged in multiple layers. Stratified columnar epithelia are found in the conjunctiva of the eye, in parts of the pharynx, anus, the uterus, and the male urethra and vas deferens.
The basal layer of this tissue is cuboidal, and becomes increasingly flattened as it reaches the surface. Stratified squamous epithelia can be keratinized or nonkeratinized, depending on the location it is found in. Keratinized epithelium, also called "cornified" is composed of numerous layers of dead squamous cells.
- In keratinized stratified squamous epithelium the outermost layer is composed of tightly packed dead cells filled with the protein keratin. Keratin is the same protein which makes up hair and fingernails. The layer of keratin-filled cells acts as water-proofing.
- Simple squamous epithelial cells in the kidney enable rapid filtration of the blood and diffusion of small molecules. This process allows the kidneys to remove waste products and excess water from the body in the urine.
- Ciliated pseudostratified columnar epithelium cells are found in places such as the trachea and upper respiratory tract, where their cilia and mucous secretions help collect foreign materials so you can cough or sneeze them out.
The layer of keratin here is named the stratum corneum. A stratified squamous epithelium consists of squamous (flattened) epithelial cells arranged in layers upon a basal membrane. Only one layer is in contact with the basement membrane; the other layers adhere to one another to maintain structural integrity.
- Stratified squamous epithelium.
Function: protects underlying tissues in areas subject to abrasion.
Location: nonkeratinized type forms the moist lining of the esophagus, mouth, and vagina; keratinized type forms the epidermis of the skin, a dry membrane.
- Stratified columnar epithelia are found in the conjunctiva of the eye, in parts of the pharynx, anus, the uterus, and the male urethra and vas deferens. It is also found in the lobar ducts in salivary glands.
- The esophageal lining is protected by a stratified squamous epithelium. Because this epithelium is normally not exposed to dryness or to abrasion, it is non-keratinized. A well-developed muscularis provides peristaltic propulsion of food. (Even when upside down, the esophagus can push food and drink to the stomach.)
Updated: 23rd October 2018