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.
Acne, including cystic acne, is not caused by: 1  Chocolate, nuts, or greasy foods. 2  Most other dietary choices-research has found an association between intake of milk products and acne, as well as a high glycemic index diet and acne. 3  Poor hygiene or inadequate face washing.4  Masturbation or sex.cne, including cystic acne, is not caused by: 1  Chocolate, nuts, or greasy foods. 2  Most other dietary choices-research has found an association between intake of milk products and acne, as well as a high glycemic index diet and acne. 3  Poor hygiene or inadequate face washing.