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.
Eating or drinking too much sugar curbs immune system cells that attack bacteria. This effect lasts for at least a few hours after downing a couple of sugary drinks. Eat more fruits and vegetables, which are rich in nutrients like vitamins C and E, plus beta-carotene and zinc.