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.
Scientists claim that eating certain foods, such as greasy foods or chocolate, does not cause acne. However, food allergies can-and do-cause acne, which is the case of gluten and acne. Eating a 100% gluten free diet is the only solution for acne that is caused by gluten.