In this lesson, you will learn the unique characteristics of pseudostratified columnar epithelium tissue, the difference between the two types, as well as where they are located.
Types of Epithelial Cells
There are two categories of tissue type: simple and stratified epithelium. Simple epithelium are those tissues composed of a single layer of cells, while stratified epithelium are tissues composed of multiple layers of cells. Each category has three subtypes based on the shape of the cells themselves. Squamous cells are flat and scale-like; cuboidal cells are cube-shaped; and columnar cells are tall and rectangular like the columns of a building. So with that said, I’m sure you are wondering how pseudostratified columnar epithelium fit into this classification structure.
To really understand this tissue, we’re going to start by breaking down the name.
Pseudostratified Columnar Epithelium
I know pseudostratified columnar epithelium might sound like an unnecessarily long name, but each element of this term specifies something unique about this tissue type.When we refer to something as ‘pseudostratified,’ we mean it has a ‘pseudo’ (false) stratification, or that it appears as if it is layered when it’s actually a single layer of cells. The cells appear stratified or layered, because they are so tightly packed together that their nuclei are forced into what looks like two layers.
So what defines this pseudostratified tissue as a single layer? Well, while the cells of this tissue are all of different heights – meaning not every cell has an apical surface, or a surface that makes direct contact with the lumen, which is the interior cavity of the organ or structure – they do each have a basal side, which makes direct contact with the connective or muscular layer of tissue below it. It is this basal side that differentiates pseudostratified tissue from stratified tissue, where only the lowest layer of cells touches the underlying tissue.If we continue decoding the term, we come to the term columnar, which, just as previously described, means that these cells are column-like in appearance. Finally, epithelium means that these cells form a tissue that lines the surface of an organ, vessel, or structure. Therefore, pseudostratified columnar epithelium is a falsely striated tissue (and therefore, a single layer of cells) composed of columnar-shaped cells that line an organ or cavity space.
Ciliated Versus Non-Ciliated
There are actually two forms of pseudostratified columnar epithelium. Ciliated epithelium cells have cilia, which are 200-300 small, hair-like protrusions on the luminal surface; and non-ciliated epithelium cells have a smooth apical side.
Function and Location
Because pseudostratified columnar epithelium are thick cells, they are useful in the process of absorbing and secreting substances as well as in creating a barrier between substances flowing through the cavity space and underlying tissues. These tightly bunched cells also protect you by ensuring that foreign substances don’t enter your bloodstream.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.
They are also found in the fallopian tubes, where ciliary movement propels the egg toward the uterus.Non-ciliated pseudostratified columnar epithelium cells are found in the vas deference, epididymis, and parts of the urethra, where mucous secretions help maintain a barrier between the luminal environment and the tissue.
Pseudostratified columnar epithelium is tissue composed of a single layer of columnar cells that line the space of an organ cavity or vessel.
It is particularly useful in the secretion and absorption of substances and is found in the upper respiratory tract and fallopian tubes (ciliated), as well as the epididymis, vas deference and urethra (non-ciliated).
Pseudostratified Columnar Epithelium Vocabulary & Definitions
- Stratified Epithelium: tissues composed of multiple layers of cells
- Squamous Cells: are flat and scale-like
- Cuboidal Cells : are cube-shaped
- Columnar Cells: tall and rectangular like the columns of a building
- Pseudostratified Columnar Epithelium: false striated tissue consisting of a single layer of columnar cells
- Ciliated: used in secretion and absorption in the upper respiratory tract and fallopian tubes
- Non-ciliated: found in the epididymis, vas deference and urethra
After analyzing this lesson in its entirety, confirm your ability to:
- Compare the categories of epithelial cells
- Dissect the term ‘pseudostratified columnar epithelium’
- Contrast ciliated and non-ciliated epithelium cells
- Highlight the function and location of these ciliated and non-ciliated cells