Final answer:
A pustule is a small, raised, pus-filled skin lesion resulting from infection or inflammation, often seen in conditions such as acne and impetigo. It is caused when the skin is damaged, allowing infection by bacteria like Propionibacterium acnes, which can lead to various forms of skin lesions.
Step-by-step explanation:
A pustule is a type of skin lesion that is pus-producing; it is usually associated with dermatological responses to damage or infection. Pustules are characterized as small, raised bumps on the skin that are fluid- or pus-filled, presenting as a result of the inflammatory response to bacterial infections like acne or impetigo. The pus in these lesions consists of a mixture of inflammatory cells and bacteria. Skin conditions like acne involve the inflammation of hair follicles, which can lead to the formation of various types of lesions including pustules, especially when the hair follicles become clogged and infected by bacteria such as Propionibacterium acnes.
In the context of impetigo, pustules can rupture, becoming crusted sores, which is a common presentation of this bacterial skin infection. Both impetigo and acne exemplify how damage to the skin, whether through blockage of hair follicles or via direct injury, can provide a pathway for bacteria to cause localized or even systemic infections by entering deeper tissues.