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.
Coffee can cause acne in a variety of ways: 1  Coffee magnifies your bodyâs stress response, boosting stress hormones that lead to acne. 2  Coffee drinks are often spiked with milk and sugar, which are two of the top four dietary acne triggers.