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three-dimensional – adj. having or seeming to have length, width, depth
breakthrough – n. an important discovery or development
vessel – n. small tube that carries blood through the body
transplant – v. operation in which a new organ is put into someone's body
patch – n. piece of material use to repair damaged parts of something
challenge – n. a difficult task or problem
routinely – adv. regularly or often
complication – n. a new medical problem that develops when someone is being treated for an illness
regulation – n. an official rule that controls how something is done
protocol – n. rules about what you must do and how you must behave in official situations
