Final answer:
Acne vulgaris involves the hair follicles, becoming clogged with sebum and dead skin cells, leading to whiteheads and blackheads, and can become infected by bacteria.
Step-by-step explanation:
The structures involved in acne vulgaris are hair follicles. Acne is a common skin condition that often occurs on areas of the skin with a high concentration of sebaceous glands, such as the face and back.
The overproduction and accumulation of sebum, along with keratin, can block hair follicles. This blockage can lead to the formation of comedones, which can be either whiteheads or blackheads depending on whether they are covered by skin or exposed to air, causing oxidation.
When the clogged hair follicles become infected with bacteria like Propionibacterium and Staphylococcus, acne lesions such as papules, pustules, and nodules occur, leading to the characteristic red and inflamed appearance of acne. Therefore, the correct answer to the question is c) Hair follicles.