Quick Facts
The tunica intima of a blood vessel is made up of endothelial cells surrounded by longitudinal elastic fibers and connective tissue (Dorland, 2011).
Related parts of the anatomy
Structure
The tunica intima is the innermost and narrowest layer of the artery. It’s formed by an endothelium, basement membrane, lamina propria, and an internal elastic membrane.
The endothelial layer arises from a single continuous layer of endothelial cells. These cells are in direct contact with blood in the lumen. Overlying this is the basement membrane, which is composed of the basal lamina and the reticular lamina. Epithelial cells and collagen fibers make up the basal lamina, while the reticular lamina is secreted by connective tissue cells and contains reticular fibers. The internal elastic lamina separates the tunica intima from the tunica media.
Anatomical Relations
In smaller arterioles or venules, the tunica intima is usually a single coating of cells, although thickness can differ in larger vessels such as the aorta. Surrounding the tunica intima is a narrow membrane of elastic fibers running parallel to the vessel.
Function
The tunica intima acts as a barrier between the blood in the lumen and the vessel walls. This barrier function results in the tunica intima partly assisting in the regulation of capillary exchange. Through release of endothelins from the endothelium, the tunica intima can alter blood pressure (Pawlina, 2016). These local chemicals can cause constriction of the smooth muscle within the walls of the vessel. The tunica intima also impedes thrombosis through hindering attachment of blood cells to the vessel wall.
List of Clinical Correlates
—Thrombosis
References
Dorland, W. (2011) Dorland's Illustrated Medical Dictionary. 32nd edn. Philadelphia, USA: Elsevier Saunders.
Pawlina, W. 2016. Histology: A text and atlas with correlated cell and molecular biology. 7th ed. Philadelphia: Wolters Kluwer.
