Scientists have discovered capillaries have a unique method of expelling debris, such as blood clots, cholesterol or calcium plaque, that blocks the flow of essential nutrients to brain cells. The capillaries spit out the blockage by growing a membrane that envelopes the obstruction and then shoves it out of the blood vessel. Scientists also found this critical process is up to 50 percent slower in an aging brain and likely results in the death of more capillaries.