Tunica interna

Tunica interna or intima is the innermost layer of an artery or vein. It is made up of one layer of endothelial cells and is supported by an internal elastic lamina. The endothelial cells are in direct contact with the blood flowing through the artery or vein.

Structure

The tunica interna is composed of three layers: the endothelium, the basement membrane, and the internal elastic lamina. The endothelium is the innermost layer and is in direct contact with the blood. It is a single layer of squamous endothelial cells that are flattened and aligned in the direction of blood flow. The basement membrane provides support for the endothelium and regulates exchange of materials between the blood and tissues. The internal elastic lamina is a layer of elastic fibers that provides structural support and elasticity to the artery or vein.

Function

The primary function of the tunica interna is to provide a smooth surface for the flow of blood, reducing friction and preventing blood clot formation. The endothelial cells produce substances that inhibit platelet adhesion and aggregation, and promote vasodilation. The basement membrane regulates the exchange of materials between the blood and tissues. The internal elastic lamina allows the artery or vein to stretch and recoil with changes in blood pressure.

Clinical significance

Damage to the tunica interna, such as from atherosclerosis or hypertension, can lead to cardiovascular diseases such as heart attack or stroke. The endothelial cells play a key role in vascular health, and their dysfunction is a major factor in the development of these diseases.

See also

• Tunica media
• Tunica externa
• Endothelium
• Artery
• Vein