The Ecology of Humans (26-2) Anatomy


The brain’s importance to the body is emphasized by its physical protection. While capillaries in other parts of the body allow cells to absorb harmful substances from the blood, the brain has a blood-brain barrier: a filter that grants limited permeability.

Membranes in the brain’s blood vessels screen out many substances of questionable integrity. Pharmaceutical makers have been daunted in trying to deliver drugs past the blood-brain barrier.