Final answer:
The difference between closed (whiteheads) and open (blackheads) comedones is the size of the follicle opening, known as the pore. Pores are the pathways for oil (sebum) to reach the skin surface, and when clogged, they form acne.
Step-by-step explanation:
The difference between closed and open comedones is the size of the follicle opening, or a. Pore. Closed comedones, or whiteheads, are follicles that are completely blocked, while open comedones, or blackheads, have a wider opening which allows the contents of the follicle to oxidize and appear black. Each pore on your skin corresponds to a follicle, which includes a hair and a sebaceous gland. This gland produces sebum that normally helps to waterproof and moisturize the hair and skin. However, excess sebum, along with dead skin cells and bacteria, can lead to acne by clogging the follicles.