The endothelial cells are present in the walls of the blood vessels that help in the entry and exit of specific molecules in and out of the blood vessels.

The endothelial cells are specialized cells that allow the permeability of selective materials through the walls of the blood vessels. These help in the movement of chemicals that facilitate in vasoconstriction and vasodilation such as epinephrine. These also allow movement of the white blood cells from the blood vessels to the site where immune defence is required to fight against foreign particles. These also help to release certain molecules from the blood at the site of the injury to assist in the formation of the clot.

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Key Points

• Endothelial cells are present in the walls of the blood vessels that allow movement of materials in and out of the vessels.

• White blood cells, chemicals involved in clot formation and chemicals involved in constriction and dilation of blood vessels can pass through these cells.

Key Terms

Vasoconstriction: narrowing of blood vessel

Vasodilation: widening of blood vessel

Blood vessels: collective term for arteries and veins

Endothelial cells: the cells that line the interior surface of blood vessels

Permeability: the ability to allow substance pass-through it