Inflamed artery. Light micrograph of a section through tissue from an inflamed artery. The artery wall (pink) encloses a narrowed central space (the lumen, white). This narrowing is due to the artery being inflamed, a condition known as arteritis. In this case, it is the inner lining of the artery, the endarterium or arterial tunica intima, which is inflamed, and this is called endarteritis. Scar (fibrous) tissue has also formed. Endarteritis can be a symptom of advanced syphilis. Magnification unknown.