What are the differences between epithelial and endothelial cells?

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Accepted Answer

Epithelial and endothelial cells are two types of cells that line body surfaces. There are several intrinsic differences between these cell types.

Basis of differentiation
Epithelial cells
Endothelial cells

Definition 
Epithelial cells refer to all types of animal cells that line the outer surfaces of organs and blood vessels and in surfaces of cavities. 
Endothelial cells are a type of epithelial cell. They line the interior surface of the circulatory and lymphatic system.

Lining
They line both the internal and external surfaces of the body
They line only the internal surfaces of cavities

Types
The cells may be squamous, cuboidal or columnar
The cells are exclusively squamous.

Structures & number of cell layers
Epithelial cells are usually packed tightly like bricks and may consist of a single layer or multiple layers. The cells have different types of structures, which offer protection against damage from the external environment
Endothelial cells consist of a single layer of squamous cells. The mono-layered structure allows water and oxygen molecules to pass easily into the surrounding tissue.

Funciton
Main functions of the epithelium include protection, secretion, absorption, and transportation.
The major function is to regulate blood flow in the blood vessels. The cells also provide slippery, non-sticky surfaces to facilitate the smoother flow of fluids

Filaments
Epithelial cell structures are supported by keratin filaments.
Endothelial cells are supported by vimentin filaments.

Surface layer
Papillary projections may be visible on the surface of some epithelial cells. 
Endothelial cells have a smooth surface without any projections.

Basis of differentiation	Epithelial cells	Endothelial cells
Definition	Epithelial cells refer to all types of animal cells that line the outer surfaces of organs and blood vessels and in surfaces of cavities.	Endothelial cells are a type of epithelial cell. They line the interior surface of the circulatory and lymphatic system.
Lining	They line both the internal and external surfaces of the body	They line only the internal surfaces of cavities
Types	The cells may be squamous, cuboidal or columnar	The cells are exclusively squamous.
Structures & number of cell layers	Epithelial cells are usually packed tightly like bricks and may consist of a single layer or multiple layers. The cells have different types of structures, which offer protection against damage from the external environment	Endothelial cells consist of a single layer of squamous cells. The mono-layered structure allows water and oxygen molecules to pass easily into the surrounding tissue.
Funciton	Main functions of the epithelium include protection, secretion, absorption, and transportation.	The major function is to regulate blood flow in the blood vessels. The cells also provide slippery, non-sticky surfaces to facilitate the smoother flow of fluids
Filaments	Epithelial cell structures are supported by keratin filaments.	Endothelial cells are supported by vimentin filaments.
Surface layer	Papillary projections may be visible on the surface of some epithelial cells.	Endothelial cells have a smooth surface without any projections.

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