Difference Between Squamous Epithelium and Columnar Epithelium

The main difference between squamous epithelium and columnar epithelium is that the squamous epithelium is made up of flat, irregular cells whereas the columnar epithelium is made up of tall, pillar-like cells. Furthermore, the two main types of squamous epithelium in the body are simple and stratified squamous epithelium while the three main types of columnar epithelium are simple, pseudostratified, and stratified columnar epithelium.

Squamous epithelium and columnar epithelium are two types of epithelia found in the body. The main function of the epithelial tissue is to line the inner body cavities and outer body surfaces.

Key Areas Covered

1. What is Squamous Epithelium
     – Definition, Types, Location, Function
2. What is Columnar Epithelium
     – Definition, Types, Location, Function
3. What are the Similarities Between Squamous Epithelium and Columnar Epithelium
     – Outline of Common Features
4. What is the Difference Between Squamous Epithelium and Columnar Epithelium
     – Comparison of Key Differences

Key Terms

Pseudostratified Columnar Epithelium, Simple Columnar Epithelium, Stratified Columnar Epithelium, Simple Squamous Epithelium, Stratified Squamous Epithelium

What is Squamous Epithelium

Squamous epithelium is the epithelium with flat or scale-like cells with a centrally-located nucleus. The two types of squamous epithelia are simple squamous and stratified squamous epithelium. The location and the function of the two types of squamous epithelia are as follows.

Squamous Epithelium – Location and Function

Simple Squamous Epithelium

This is a single epithelial cell layer on the basement membrane.

Location:

• Lining of the heart, blood vessels, and lymphatic vessels
• Air sacs of the lungs

Function:

• Allows the passage of materials through diffusion or filtration
• Secretes mucus

Stratified Squamous Epithelium

This refers to several epithelial cell layers on the basement membrane.

Location:

• Lining of the mouth, esophagus, and vagina
• Lining of the human skin

Function:

• Protects the body internal against abrasion

Figure 1: Stratified Squamous Epithelium

The stratified squamous epithelium consists of three layers: basal layer, intermediate layer, and superficial layer. It is the type of epithelium that makes up the skin of humans. In the corneal epithelium, lining mucosa of oral cavity, esophagus, anal canal, vagina, ectocervix, foreskin, and the internal portion of the lips, the superficial layer is non-keratinized while the other areas of the skin contain a keratinized, superficial layer.  

What is Columnar Epithelium

Columnar epithelium contains column-shaped cells. This means the cells of this epithelium are taller and thinner. The nuclei are elongated and found near the base of the epithelial cells. The three main types of columnar epithelia are simple columnar, pseudostratified columnar, and stratified columnar epithelium. The location and the function of the three types of columnar epithelia are as follows:

Columnar Epithelium – Location and Function

Simple Columnar Epithelium

This is a single epithelial cell layer on the basement membrane. 

Location:

• Lining of the bronchi, uterus, and uterine tubes (ciliated)
• Lining of the digestive tract and bladder (nonciliated)

Function:

• Secrets mucus and enzymes
• Absorb nutrients

Pseudostratified Columnar Epithelium

This is a single epithelial cell layer on the basement membrane; nuclei occur in different heights.

Location:

• Lining of the trachea and upper respiratory tract (ciliated)

Function:

• Secretes and moves mucus

Stratified Columnar Epithelium

These are several epithelial cell layers on the basement membrane.

Location:

• Lining of the male urethra
• Lining of some glands

Function:

• Protects the body internal against abrasion
• Secretes mucus

Figure 2: Simple Columnar Epithelium

In addition to protection, the main function of the columnar epithelium is to secrete and pass mucus. The specialized cells called Goblet cells in the epithelium are responsible for the production and secretion of mucus. The movement of cilia on the surface of the epithelium facilitates the movement of mucus with trapped particles in it to the outside of the body.

Similarities Between Squamous Epithelium and Columnar Epithelium

• Squamous epithelium and columnar epithelium are two types of epithelial tissue found in the body.
• Their main function to line the body cavities.
• The arrangement of epithelial cells occurs on the basement membrane, which is continuous with the underlying connective tissue.
• The adjacent cells are connected together through cell junctions.
• Epithelial tissue does not contain blood vessels inside it; hence, the cells of the epithelium get nutrients through diffusion.

Difference Between Squamous Epithelium and Columnar Epithelium

Definition

Squamous epithelium refers to an epithelium that consists of one or several cell layers of flat, scale-like or plate-like cells while columnar epithelium refers to an epithelial tissue comprised of columnar epithelial cells, with or without cilia, and is involved primarily in secretory, absorptive, or excretory functions. The difference between squamous epithelium and columnar epithelium is explicit from this definition.

Types

Simple and stratified squamous epithelium are the two main types of squamous epithelium while simple, pseudostratified, and stratified columnar epithelium are the three main types of columnar epithelium.

Nuclei

Another difference between squamous epithelium and columnar epithelium is in their nuclei. Nuclei of the squamous epithelium are centrally located while the nuclei of the columnar epithelium are mainly located at the bottom.

Cilia

Further difference between squamous epithelium and columnar epithelium is the cilia. Squamous epithelium does not contain cilia while columnar epithelium except stratified columnar epithelium contains cilia.

Location

Moreover, the squamous epithelium mainly occurs in the passages that open to the external environment while the columnar epithelium mainly occurs in the inner body surfaces.

Also, functionally too, there are differences between squamous epithelium and columnar epithelium.

Secretory Function

Squamous epithelium does not perform a secretory function while columnar epithelium secretes mucus and enzymes.

Function

Squamous epithelium allows molecules to pass through diffusion while columnar epithelium moves the mucus out of the body.

Conclusion

Squamous epithelium contains flat cells that allow the movement of molecules across it. Columnar epithelium contains column-like cells that allow the secretion of mucus and the movement of mucus by the movement of cilia. Therefore, the main difference between squamous epithelium and columnar epithelium is their structure and function.

Reference:

1. “Boundless Anatomy and Physiology.” Lumen, Open SUNY Textbooks, Available Here

Image Courtesy:

1. “Epithelial Tissues Stratified Squamous Epithelium (40230842160)” By Berkshire Community College Bioscience Image Library – Epithelial Tissues: Stratified Squamous Epithelium (CC0) via Commons Wikimedia  
2. “Epithelial Tissues Mucous Glands in Simple Columnar Epithelium (27854454278)” By Berkshire Community College Bioscience Image Library – Epithelial Tissues: Mucous Glands in Simple Columnar Epithelium (CC0) via Commons Wikimedia