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.
Summary: 1  Foods donât have a tremendous influence on acne either for better or for worse. 2  Dark chocolate triggers pimple production in people who already have acne but milk chocolate usually does not. 3  Cowâs milk may trigger blemishes, but the problem is the hormones in the milk, not milk fat.