The blood-brain barrier is formed by brain endothelial cells connected by tight junctions with extremely high electrical resistivity.

The blood-brain barrier is formed by brain endothelial cells connected by tight junctions with extremely high electrical resistivity.

• A. Brain endothelial cells connected by tight junctions with extremely high electrical resistivity
• B. Neurons that create the barrier
• C. Glial cells forming the barrier
• D. Blood vessels without tight junctions

Answer: (A)

The barrier is formed by brain capillary endothelial cells that line the CNS vessels and are joined together by tight junctions. These tight junctions create a very high transendothelial electrical resistance, effectively sealing the paracellular route and controlling what can pass from blood into brain tissue. Neurons aren’t responsible for forming this barrier, and while glial cells like astrocytes influence and support barrier properties, the primary structural barrier is the endothelial layer with tight junctions. Blood vessels without tight junctions would be leaky and fail to protect neural tissue.

The barrier is formed by brain capillary endothelial cells that line the CNS vessels and are joined together by tight junctions. These tight junctions create a very high transendothelial electrical resistance, effectively sealing the paracellular route and controlling what can pass from blood into brain tissue. Neurons aren’t responsible for forming this barrier, and while glial cells like astrocytes influence and support barrier properties, the primary structural barrier is the endothelial layer with tight junctions. Blood vessels without tight junctions would be leaky and fail to protect neural tissue.