Abdominal aorta histologic cross sections (a) a short distance distal to the IMA ostium. S3, female, age 32.1 year old. The fibrous intima (purple/blue) is easily distinguished from the muscular media (red) (b) infraIMA region. S1, female, age 18.7 year old. Elastic trichrome stain. L – Left, R – Right, A – Anterior, LU – Lumen. The pairs of arrows denote the intimal thickness on the posterior wall.