Pseudostratified columnar epithelium is a type of

epithelium Epithelium or epithelial tissue is a thin, continuous, protective layer of cells with little extracellular matrix. An example is the epidermis, the outermost layer of the skin. Epithelial ( mesothelial) tissues line the outer surfaces of man ...

that, though comprising only a single layer of

cells Cell most often refers to: * Cell (biology), the functional basic unit of life * Cellphone, a phone connected to a cellular network * Clandestine cell, a penetration-resistant form of a secret or outlawed organization * Electrochemical cell, a d ...

, has its

cell nuclei The cell nucleus (; : nuclei) is a membrane-bound organelle found in eukaryotic cells. Eukaryotic cells usually have a single nucleus, but a few cell types, such as mammalian red blood cells, have no nuclei, and a few others including osteoc ...

positioned in a manner suggestive of

stratified columnar epithelium Stratified columnar epithelium is a rare type of epithelial tissue composed of column-shaped cells arranged in multiple layers. It is found in the conjunctiva, pharynx, anus, and male urethra. It also occurs in embryo. Location Stratified col ...

. A stratified epithelium rarely occurs as

squamous Epithelium or epithelial tissue is a thin, continuous, protective layer of cells with little extracellular matrix. An example is the epidermis, the outermost layer of the skin. Epithelial ( mesothelial) tissues line the outer surfaces of man ...

cuboidal Epithelium or epithelial tissue is a thin, continuous, protective layer of cells with little extracellular matrix. An example is the epidermis, the outermost layer of the skin. Epithelial ( mesothelial) tissues line the outer surfaces of many ...

. The term ''pseudostratified'' is derived from the appearance of this epithelium in the section which conveys the erroneous (''pseudo'' means almost or approaching) impression that there is more than one layer of cells, when in fact this is a true simple epithelium since all the cells rest on the

basement membrane The basement membrane, also known as base membrane, is a thin, pliable sheet-like type of extracellular matrix that provides cell and tissue support and acts as a platform for complex signalling. The basement membrane sits between epithelial tis ...

. The nuclei of these cells, however, are disposed at different levels, thus creating the illusion of cellular stratification. All cells are not of equal size and not all cells extend to the luminal/apical surface; such cells are capable of cell division providing replacements for cells lost or damaged. Pseudostratified epithelia function in secretion or absorption. If a specimen looks stratified but has

cilia The cilium (: cilia; ; in Medieval Latin and in anatomy, ''cilium'') is a short hair-like membrane protrusion from many types of eukaryotic cell. (Cilia are absent in bacteria and archaea.) The cilium has the shape of a slender threadlike proj ...

, then it is a pseudostratified ciliated epithelium, since stratified epithelia do not have cilia. Ciliated epithelia are more common and lines the

trachea The trachea (: tracheae or tracheas), also known as the windpipe, is a cartilaginous tube that connects the larynx to the bronchi of the lungs, allowing the passage of air, and so is present in almost all animals' lungs. The trachea extends from ...

bronchi A bronchus ( ; : bronchi, ) is a passage or airway in the lower respiratory tract that conducts air into the lungs. The first or primary bronchi to branch from the trachea at the carina are the right main bronchus and the left main bronchus. Thes ...

. Non-ciliated epithelia lines the larger ducts such as the ducts of parotid glands.

Examples

* Ciliated pseudostratified columnar epithelium is the type of

respiratory epithelium Respiratory epithelium, or airway epithelium, is ciliated pseudostratified columnar epithelium a type of columnar epithelium found lining most of the respiratory tract as respiratory mucosa, where it serves to moisten and protect the airways ...

found in the linings of the

as well as upper respiratory tract, which allows filtering and humidification of incoming air. * Non-ciliated pseudostratified columnar epithelia are located in the

prostate The prostate is an male accessory gland, accessory gland of the male reproductive system and a muscle-driven mechanical switch between urination and ejaculation. It is found in all male mammals. It differs between species anatomically, chemica ...

and membranous part of male

vas deferens The vas deferens (: vasa deferentia), ductus deferens (: ductūs deferentes), or sperm duct is part of the male reproductive system of many vertebrates. In mammals, spermatozoa are produced in the seminiferous tubules and flow into the epididyma ...

. * Pseudostratified columnar epithelia with

stereocilia Stereocilia (or stereovilli or villi) are non-motile apical cell modifications. They are distinct from cilia and microvilli, but are closely related to microvilli. They form single "finger-like" projections that may be branched, with normal cel ...

are located in the

epididymis The epididymis (; : epididymides or ) is an elongated tubular genital organ attached to the posterior side of each one of the two male reproductive glands, the testicles. It is a single, narrow, tightly coiled tube in adult humans, in length; ...

. Stereocilia of the epididymis are not cilia because their cytoskeleton is composed of actin filaments, not microtubules. They are structurally and molecularly more similar to microvilli than to true cilia. * Pseudostratified columnar epithelia are found forming the straight, tubular glands of the

endometrium The endometrium is the inner epithelium, epithelial layer, along with its mucous membrane, of the mammalian uterus. It has a basal layer and a functional layer: the basal layer contains stem cells which regenerate the functional layer. The funct ...

in females. They are also found in the internal part of the

ear In vertebrates, an ear is the organ that enables hearing and (in mammals) body balance using the vestibular system. In humans, the ear is described as having three parts: the outer ear, the middle ear and the inner ear. The outer ear co ...

Additional images

File:2304 Pseudostratified Epithelium.jpg, Cross-section of pseudostratified columnar epithelium File:2308 The Trachea-b.jpg, Second cross-section of pseudostratified columnar epithelium Psuedostratified epithelium animated

References

External links

{{Authority control Epithelial cells