What Are Endothelial Cells? Function & Types

Keta Bhakta, Marta Toran
  • Author
    Keta Bhakta

    Keta Bhakta graduated from University of Minnesota with a B.S. in Neuroscience and then with a D.D.S. as a dentist. She has tutored many students in various math and science subjects. She began working as a professor at the University of Minnesota School of Dentistry in 2013.

  • Instructor
    Marta Toran

    Marta has taught high school and middle school Science and has a Master's degree in Science Education.

What are endothelium cells? Learn about these cells, the endothelium, and their endothelial function. Also, learn about the endothelium of blood vessels. Updated: 07/30/2021

Table of Contents


What are Endothelial Cells?

The definition of an endothelial cell is one that lines blood and lymphatic vessels within the body, surrounding the hollow space where liquid flows within these tubes (also known as the cavity or the lumen). These endothelial cells are only one layer thick. However, they are connected to each other using tight cell junctions to prevent anything from passing through them, and they bind to the connective tissue underneath them using an intermediate basement membrane. In a blood vessel like an artery, a thick layer of smooth muscle cells typically surrounds the endothelial cells in order to complete the structure of the blood vessel.

Lining the walls of this blood vessel is a single layer of endothelial cells.

A rendered depiction of the inside of a vein. Blood cells pass through the vessel.

Another area that contains endothelial cells is the blood-brain barrier. Blood vessels in the brain are very thin, comprised of a single layer of endothelial cells and the surrounding basement membrane. This thin structure allows for needed substances (like nutrients, neurotransmitters, and hormones) to pass efficiently in and out of the brain. However, very tight junctions exist between endothelial cells at the blood-brain barrier which only allow for selective, controlled uptake and removal of these substances. This helps to prevent anything unwanted from entering the brain and altering or damaging delicate, essential neurological processes.

Epithelial vs. Endothelial Cells

Epithelial cells are often confused for endothelial cells. These cells also act as lining, and can be found throughout the body in organs such as the skin, lungs, kidneys, and digestive tract. They allow for the absorption, excretion, and secretion of lubrication into and out of these organs. As it happens, endothelial cells are a specific subset of epithelial cell. However, endothelial cells are only found in the lining of cardiovascular and lymphatic systems.

This epidermis is comprised of epithelial cells.

A picture of the cellular structure of skin, showing the epidermis and the dermis underneath.

In order to understand and remember the difference between these two types, consider the etymology of these words. Both end with -thelial, meaning a layer. However, epi- means on or over, while endo- means within. Endothelial cells are only found in structures within the body, whereas epithelial cells can be found in surface layers like the skin.

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  • 0:00 What Are Endothelial Cells?
  • 0:43 Main Function
  • 1:42 Other Specialized Functions
  • 3:12 When Endothelial Cells…
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What is Endothelium?

The endothelium refers to the entirety of the endothelial tissue structure that lines blood and lymphatic vessels. This consists of the embryonic mesoderm, the single layer of endothelial cells, and the surrounding basement membrane.

Endothelium of Blood Vessels

The endothelium in the blood vessels, made up of vascular endothelial cells, performs essential processes for the flow of blood.

  • Relaxation and Tightening: The endothelium controls this, allowing them to respond appropriately to medications, hormones, exercise, etc.
  • Release of Substances: This allows for regulation of characteristics like blood clotting and platelet activity, encouraging or discouraging it as necessary.
  • Thickness: The endothelium's thickness varies depending on the type of blood vessel in order to reflect its needs. For example, the endothelium of a capillary is very thin to allow for easy diffusion of substances, typically comprised of only a single cell layer of cells and a basement membrane. However, the endothelium of a robust, large artery is very thick to allow for greater pumping efficiency.

Endothelial Function

The endothelial cells and the rest of the endothelium form the basic structure of these blood vessels and lymphatic vessels. In addition, endothelial cells are vital to maintaining the blood brain barrier, as well as performing specific tasks necessary for blood flow and regulation within a vessel.

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Frequently Asked Questions

What is the function of the endothelium?

The endothelium comprises the structure of the blood vessels and lymphatic vessels. It also allows for smooth vessel regulation, inflammation control, and initiation of immune response to pathogens.

Why is endothelial function important?

The endothelium controls functions such as dilation and narrowing of blood vessels in order to help with blood pressure issues. It also secretes substances to alleviate inflammation and allow blood clotting when needed.

What causes endothelial dysfunction?

Endothelial dysfunction is caused by many factors such as low oxygen, inflammation, infections, and cardiac conditions like high blood pressure.

What are four functions of endothelial cells?

The 4 main functions of endothelial cells are filtration of fluids, blood vessel size regulation, hemostasis, and transport of various substances throughout the body.

What causes damage to endothelial cells?

Many factors can damage endothelial cells such as cardiovascular diseases, infections, inflammation, plaque deposition from increased fat intake, and turbulent and resistant blood flow.

Where are your endothelial cells?

The endothelial cells are located in the lining of the cardiovascular system (arteries, veins, and capillaries) and in the vessels of the lymphatic system.

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