Final answer:
A small blister or sac containing clear fluid is known as a vesicle in biology. These are commonly found under the skin and can be caused by various conditions including impetigo, which results in pus-filled sores or ruptured blisters with a yellowish crust.
Step-by-step explanation:
A small blister or sac containing clear fluid is typically referred to as a vesicle in a biological context. These vesicles are encapsulated sacs that can contain fluid, semi-solid matter, or gas, and are usually found just below the upper layers of the skin. In human biology, blisters can result from various conditions such as mechanical irritation or certain skin infections, like impetigo.
Impetigo is a skin infection that leads to the formation of vesicles, pustules, and sometimes bullae, which are larger fluid-filled blisters. The condition can manifest around the nose and mouth and is characterized by yellowish crusts formed from ruptured lesions. Whereas, in the early stages of embryonic development, the term blastocyst is used to describe a fluid-filled ball of cells, and the blastocoel is the specific term for the fluid-filled cavity within the blastocyst.