Everything You Need to Know About Pseudostratified Columnar Epithelium. In some columnar epithelia, the cells become overly crowded/densely populated such that some of the nuclei become displaced and a number of rows of the nuclei appear in sections of the cell sheets, even though each one of the cells is still attached to the underlying basement membrane. It’s only when viewed closely and in a cross-section position that some of the cells in the epithelium are found to actually reach the surface. Because they are densely packed, these cells appear to be multiple layers rather than just a single layer.
This type of epithelia is known as Pseudostratified Columnar Epithelium. It’s most commonly found along the respiratory tract and male reproductive tract.
Types of Pseudostratified Columnar Epithelium
There are two main types of pseudostratified columnar epithelia: ciliated and non-ciliated.
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• Ciliated Pseudostratified Columnar Epithelium
The most common types of pseudostratified columnar epithelia occur as ciliated types where the presence of cilia gives the epithelial cells the ability to properly mucus along the surface. They are mostly found in the upper respiratory tract and the linings of the trachea.
• Non-ciliated Pseudostratified Columnar Epithelium
This type does not have cilia but contains stereocilia, some special kind of cytoplasmic projection. They feature long branching microvilli whose purpose is to increase the surface area of the cells lining different tubules in the body and have an absorptive or mechanosensory function. These types of epithelia are found in the male reproductive tract (vas deferens and epididymis).
Main Functions of Pseudostratified Columnar Epithelium
The pseudostratified columnar epithelium is found in different areas in the body and therefore serves different functions. They include;
• Secretion of Mucus
One of the main functions of this type of epithelium is the secretion of mucus where this function is served by goblet cells.
They are found in regions requiring the secretion of mucus to trap foreign bodies and sweep particles in order to prevent them from traveling further down the respiratory tract.
Smaller particles are eliminated as a part of the normal drainage of the nose while larger or heavier particles are coughed or sneezed out.
The pseudostratified columnar epithelium serves as the first line of defense against foreign bodies and particles, preventing them from traveling further down the lower respiratory tract.
This is made possible by the secretion of mucus.
Protecting the respiratory tract prevents the development of various health complications.
• Propulsion of Sperm
This type of epithelia is found in the male reproductive tract (vas deferens and epididymis) where it aids in the propulsion of sperm during ejaculation (1).
The stereocilia increase the surface area of the epididymis by absorbing excess fluid in the reproductive tract, thereby adding more pressure to flushing the sperm out of the body.
For decades, scientists have been performing various studies to improve our understanding of human epithelia. The goal is to discover new ways in which it can possibly improve human health.
The pseudostratified columnar epithelium is one unique type of human epithelia whose functions play a very important role in the human body, despite its amazingly variable forms.