The key difference between epithelium and endothelium is that the epithelium is the tissue that lines the outer surfaces of organs and blood vessels, as well as the inner surfaces of cavities in many internal organs while the endothelium is the tissue that lines the interior surface of blood vessels and lymphatic vessels.
A tissue is a group of physically linked cells and associated intercellular substances that are specialized for particular functions. On the basis of their structure and functions, there are four fundamental types of tissues in the animal body such as epithelial tissue, connective tissue, muscular tissue and nervous tissue. The epithelial tissue is the covering of all external and internal body surfaces. Therefore, it lines the whole external surface of the skin, internal cavities and lumens as well as the external and internal surfaces of the vessels.
Moreover, they also help the exocrine function by the formation of glands. The external epithelium is called the exothelium; it is the epithelium that covers the skin and organ lining. There are also two subtypes of the epithelium: mesoderm that lines internal cavities and lumens and the mesothelium that covers vessels and the heart chambers. Hence, essentially the endothelium is part of the epithelial tissue that helps the body protect itself from damages.
1. Overview and Key Difference
2. What is Epithelium
3. What is Endothelium
4. Similarities Between Epithelium and Endothelium
5. Side by Side Comparison – Epithelium vs Endothelium in Tabular Form
What is Epithelium?
Epithelium is the tissue that lines the outer surfaces of organs and blood vessels and inner surfaces of cavities of organs. It may have one or more cell layers that are closely packaged and arranged. There are three different shapes of epithelial cells such as squamous, columnar, and cuboidal.
True epithelial tissue has an ectodermal and endodermal embryonic origin. This tissue is avascular hence the adjoining connective tissue supplies it with food nutrients and energy through simple diffusion. Accordingly, blood and lymph vessels and nerve endings perforate the basal membrane of the epithelium for sense. These provide the functions of protection from mechanical physiological and microbial damage, secretary function of enzymes, hormones and lubricating fluids by the glandular epithelium and sensory function through the nerve endings.
Moreover, the epidermis is one of the epithelial tissues that cover our skin. Secretion, selective absorption, protection, transcellular transport and sensing are few functions of epithelial tissue.
What is Endothelium?
Endothelium is a specialized type of epithelium found in the lining of blood and lymphatic vessels. Also, it lines the heart cavities. Furthermore, this tissue has an embryonic mesodermal origin. It usually helps smooth flow of fluid upon its surface. It constitutes flattened cells adhered to a basal membrane with elastin fibres running through it. Therefore, this gives the endothelium a distensible quality and the ability to accommodate the fluctuating flow of fluid.
Likewise, endothelial cells form a sheet-like a barrier to regulate the entry of external material, microorganisms and toxins, as well as fluid flow in and out of the vessels. They are sensitive to blood pressure and secrete vasodilators such as prostacylin and Nitric oxide in response to high blood pressure. Consequently, when there is damage to the blood vessel, the endothelium secrets thromboplastin; this helps the coagulation of blood and responds to cytokinase to increases the permeability to white blood cells.
What are the Similarities Between Epithelium and Endothelium?
- Epithelium and Endothelium line body surfaces.
- Both tissues protect the body and organs.
- Furthermore, they involve secretion and sensory functions.
- Also, both have a high generative and healing capacity.
What is the Difference Between Epithelium and Endothelium?
Epithelial tissues line the outer surfaces of organs and blood vessels throughout the body, as well as the inner surfaces of cavities in many internal organs. On the other hand, endothelium refers to cells that line the interior surface of blood vessels and lymphatic vessels. Therefore, this is the key difference between epithelium and endothelium. However, endothelium is a specialized epithelial tissue that has been modified to line the interior surfaces of blood and lymph vessels.
Moreover, another difference between epithelium and endothelium is that the epithelium may have single cell layer or many cell layers. But, endothelium has a single cell layer. Furthermore, epithelium is ectodermal or endodermal origin while the endothelium is the mesodermal origin.
The below infographic represents more details on the difference between epithelium and endothelium comparatively.
Summary – Epithelium vs Endothelium
Epithelium and endothelium are two types of tissues that line outer surfaces of the body, surfaces of internal organs, blood vessels and lymphatic vessels. Summarizing the difference between epithelium and endothelium; the epithelium lines the outer surfaces of organs and blood vessels and inner surfaces of cavities in internal organs. On the other hand, endothelium lines the inner surfaces of blood vessels and lymphatic vessels. Furthermore, epithelium can have many cell layers while endothelium has only one cell layer. Moreover, epithelium has ectodermal and endodermal origin while the endothelium has a mesodermal origin. Both epithelium and endothelium fulfil similar functions such as secretion, protection and sensory function.
1. “Endothelium.” Wikipedia, Wikimedia Foundation, 27 Nov. 2018. Available here
1.”Illu epithelium” (Public Domain) via Commons Wikimedia
2.”Blausen 0055 ArteryWallStructure”By Blausen.com staff (2014). “Medical gallery of Blausen Medical 2014”. WikiJournal of Medicine 1 (2). DOI:10.15347/wjm/2014.010. ISSN 2002-4436. – Own work, (CC BY 3.0) via Commons Wikimedia