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A pseudostratified epithelium is a type of
epithelium Epithelium or epithelial tissue is one of the four basic types of animal tissue, along with connective tissue, muscle tissue and nervous tissue. It is a thin, continuous, protective layer of compactly packed cells with a little intercellul ...
that, though comprising only a single layer of
cells Cell most often refers to: * Cell (biology), the functional basic unit of life Cell may also refer to: Locations * Monastic cell, a small room, hut, or cave in which a religious recluse lives, alternatively the small precursor of a monastery w ...
, has its cell nuclei positioned in a manner suggestive of stratified epithelia. As it rarely occurs as squamous or cuboidal epithelia, it is usually considered synonymous with the term pseudostratified columnar epithelium. 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 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 tissues including mesothelium an ...
. 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, plural cilia (), is a membrane-bound organelle found on most types of eukaryotic cell, and certain microorganisms known as ciliates. Cilia are absent in bacteria and archaea. The cilium has the shape of a slender threadlike proje ...
, 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, 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 air- breathing animals with lungs. The trachea extends from t ...
, bronchi. Non-ciliated epithelia lines the larger ducts such as the ducts of
parotid glands The parotid gland is a major salivary gland in many animals. In humans, the two parotid glands are present on either side of the mouth and in front of both ears. They are the largest of the salivary glands. Each parotid is wrapped around the man ...
.


Examples

* Ciliated pseudostratified columnar epithelia is the type of respiratory epithelium found in the linings of the
trachea The trachea, 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 air- breathing animals with lungs. The trachea extends from t ...
as well as other respiratory tract, which allows filtering and humidification of incoming air. * Non-ciliated pseudostratified columnar epithelia are located in the prostate and membranous part of male vas deferens. * Pseudostratified columnar epithelia with stereocilia are located in the
epididymis The epididymis (; plural: epididymides or ) is a tube that connects a testicle to a vas deferens in the male reproductive system. It is a single, narrow, tightly-coiled tube in adult humans, in length. It serves as an interconnection between the ...
. 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 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 functional layer ...
in females. They are also found in the internal part of the ear.


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


References


External links

{{Authority control Epithelial cells