Structure and Function of Arteries, Capillaries, and Veins. The walls of arteries and veins have three layers or tunics: 1  An outer layer (tunica adventitia) of connective tissue with collagen fibers. 2  A middle layer (tunica media) of circularly arranged smooth muscle and elastic fibers.
You might have heard that eating chocolate or greasy foods can cause acne, but these are both just myths. The truth is that food has little to do with breakouts. Acne occurs when the openings of hair follicles become blocked with oil secretions, dead skin cells and bacteria.
Photo: Levi Brown/Trunk Archive. Acne is a complex issueâthereâs no single cause of breakouts, and what triggers a pimple in one person might be benign to another. With that said, if topical treatments havenât made a difference, it may be time to change what you eat. More doctors and estheticians than ever believe in a diet-acne connection, and some common foods are now believed to be breakout triggers. Here, 7 foods that can make acne worse. (On the bright side, chocolate is not on the list.).