Difference Between Epithelial and Endothelial Cells

Main Difference – Epithelial vs Endothelial Cells

Epithelial cells and endothelial cells are two types of cells that line body surfaces. Endothelial cells are a specialized type of epithelial cells. The main difference between epithelial and endothelial cells is that epithelial cells line both internal surfaces and external surfaces of the body whereas endothelial cells line the internal surfaces of the components of the circulatory system. Epithelial cells can be identified in three shapes. They are squamous, cuboidal, and columnar. Depending on the number of cell layers in it, two types epithelia can be identified; simple epithelium and stratified epithelium. But, endothelial cells are made up of simple squamous epithelium.

Key Areas Covered

1. What are Epithelial Cells
      – Definition, Characteristics, Function
2. What are Endothelial Cells
      – Definition, Characteristics, Function
3. What are the Similarities Between Epithelial and Endothelial Cells
      – Outline of Common Features
4. What is the Difference Between Epithelial and Endothelial Cells
      – Comparison of Key Differences

Key Terms: Apical Basal Polarity, Basal Lamia, Columnar Epithelium, Cuboidal Epithelium, Endothelial Cells, Epithelial Cells, Simple Epithelium, Squamous Epithelium, Stratified Epithelium

What are Epithelial Cells

Epithelial cells refer to any type of animal cells that cover the surfaces or line a cavity, performing secretory, transporting, or regulatory functions. Apical basal polarity is one of the major characteristics of the epithelium. This means the basal surface of the epithelial cells are attached to the basal lamina and the apical surface of the cells face the lumen. Epithelial cells are arranged together to create a continuous sheet, by forming desmosomes and tight junctions. The basal lamina is attached to a connective tissue layer called the reticular lamina. No blood supply can be found between epithelial cells (avascular). Moreover, there is no nerve supply in it (innervated). Epithelial cells exhibit a high regenerative capacity as well. Epithelial cells are shown in figure 1.

Figure 1: Epithelial Cells

Three types of cells occur in the epithelium. They are squamous, cuboidal, and columnar. The squamous epithelium comprises flat and scale-like cells. The cuboidal cells are block-like and the columnar cells are tall. These three cell types are either arranged into a single cell layer or several cell layers. When an epithelium comprises a single layer of epithelial cells, it is called the simple epithelium. On the other hand, several epithelial cell layers produce a stratified epithelium.

Figure 2: Epithelial Cell Location and Function

The pseudostratified epithelium is an alternative type of epithelium whose cell height varies. Transitional epithelium is another type of epithelia that allows urinary organs to be stretched. Some epithelial cells contain projections and cilia. The type, location, and the function of the epithelial cells are shown in figure 2.

What are Endothelial Cells

Endothelial cells are a type of epithelial cells that line the cavities of the circulatory system. They are composed of simple squamous epithelial cells. Endothelial cells line the lumen of the arteries, veins, and the blood capillaries. The cavities of the heart are also lined by endothelial cells. Endothelial cells line the lumens of the lymphatic vessels as well. The endothelial cells in a cross-section of a blood vessel are shown in figure 3.

Figure 3: Endothelial Cells in a Blood Vessel

The main function of the endothelial cells is to provide a slippery but, non-sticky surfaces for the free-flow of blood. The surface of the endothelial cells is soft. White blood cells are capable of moving from the blood to the tissues through the endothelium. Therefore, endothelial cells serve as a semi-selective barrier to the components of the blood. Due to the high regeneration power of the endothelial cells, they are involved in the formation of blood vessels (angiogenesis). Endothelial cells also aid in blood clotting. They control the blood pressure by changing the diameter of the lumen in processes called vasoconstriction and vasodilation.

Similarities Between Epithelial and Endothelial Cells

• Both epithelial and endothelial cells line the surfaces of the body.
• The basal surface of both epithelial cells and the endothelial cells are attached to the basement membrane while the apical surface faces the lumen.
• Both epithelial and endothelial cells possess a high regenerative power.

Difference Between Epithelial and Endothelial Cells

Definition

Epithelial Cells: Epithelial cells refer to any type of animal cells that cover the surfaces or line a cavity, performing secretory, transporting, or regulatory functions.

Endothelial Cells: Endothelial cells are a type of epithelial cells that line the cavities of the circulatory system.

Lining

Epithelial Cells: Epithelial cells line both internal surfaces and external surfaces of the body.

Endothelial Cells: Endothelial cells line the internal surfaces of the components of the circulatory system.

Types

Epithelial Cells: Epithelial cells can be squamous, cuboidal or columnar.

Endothelial Cells: Endothelial cells are made up of squamous epithelial cells.

Number of Cell Layers

Epithelial Cells: Epithelial cells consist of either single or several cell layers.

Endothelial Cells: Endothelial cells consist of a single squamous cell layer.

Function

Epithelial Cells: Secretion, transport, sense, and regulation are the functions of the epithelial cells.

Endothelial Cells: The major function of the endothelial cells is to provide slippery, non-sticky surfaces for the flow of fluids.

Filaments

Epithelial Cells: Epithelial cells comprise keratin filaments.

Endothelial Cells: Endothelial cells comprise intermediate filaments.

Surface Layer

 Some of the epithelial cells may contain papillary projections.

Endothelial Cells: The surface of the endothelial cells is smooth.

Conclusion

Epithelial and endothelial cells are two types of cells that line the cavities of the animal body. Epithelial cells line the external surfaces of the body as well. Endothelial cells mainly line the cavities of the circulatory system. Epithelial cells can be either simple or stratified and squamous, cuboidal or columnar. Endothelial cells are simple squamous epithelial cells. The main difference between epithelial and endothelial cells is their structure, location, and the function.

Reference:

1. “Epithelial Tissue.” Anatomy & Physiology, 29 Feb. 2016, Available here. Accessed 3 Oct. 2017.
2. “Endothelial Cells and Functions.” Lonza, Available here. Accessed 3 Oct. 2017.

Image Courtesy:

1. “Ciliated columnar epithelium” By Todd Straus and Vladimir Osipov – BioMed Central (CC BY 3.0) via Commons Wikimedia
2. “423 Table 04 02 Summary of Epithelial Tissue CellsN” By OpenStax College – Anatomy & Physiology, Connexions Web site, Jun 19, 2013 (CC BY 3.0) via Commons Wikimedia
3. “Endotelijalna ćelija” By DRosenbach at English Wikipedia (CC BY-SA 3.0) via Commons Wikimedia