Figure 3-7. Plaque.
(7) Vesicle and bulla. A vesicle (figure 3-8) is an elevated, fluid-filled skin
lesion that is less than 0.5 cm in diameter. A bulla is the same as a vesicle with the
exception that the bulla is greater than 0.5 cm in diameter. A vesicle or bulla arises
from a cleavage at various levels of the skin. When the cleavage is just beneath the
stratum corneum of the skin, a subcorneal vesicle or bulla results as in impetigo and
corneal pustular dermatosis. Sometimes the vesicle or bulla walls are so thin that you
can see through them. In such instances, the serum, lymph, blood, or extracellular fluid
is quite visible.
Figure 3-8. Types of vesicles.