How does a vesicle differ in size from a bulla?

The distinction between a vesicle and a bulla revolves around their respective sizes. A vesicle is defined as a fluid-filled blister that is less than 0.5 cm in diameter, typically containing serous fluid. This size classification is important for clinicians to correctly identify and treat dermatological conditions.

In contrast, a bulla is larger, exceeding 0.5 cm in diameter, and may also contain fluid but is characterized by its larger size. Understanding this size difference is crucial in both diagnosis and creating an appropriate treatment plan for skin conditions that present with these types of lesions.

The correct answer highlights this critical size-based distinction, helping to clarify the terminology used in dermatology and other medical fields.