vesicle
"So a vesicle is like a soap bubble - very small - and it is surrounded by a membrane, just like a soap bubble is surrounded by a film of soap, and inside it is the neurotransmitter. And the entire presynapse, or presynaptic neuron terminal, is also surrounded by a membrane."
"The word comes from the Latin for "little bladder." Vesicles that fill with minerals are called amygdules; that is, if a vesicle is like a mold, an amygdule is like a cast"
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