Question

plz explain blood brain barrier (BBB)

Answer 1

The blood–brain barrier (BBB) is a highly selective semipermeable border that separates the circulating blood from the brain and extracellular fluid in the central nervous system (CNS). The blood–brain barrier is formed by endothelial cells of the capillary wall, astrocyte end-feet ensheathing the capillary, and pericytes embedded in the capillary basement membrane. This system allows the passage of water, some gases, and lipid-soluble molecules by passive diffusion, as well as the selective transport of molecules such as glucose and amino acids that are crucial to neural function. Specialized structures participating in sensory and secretory integration within neural circuits –the circumventricular organs and choroid plexus – do not have a blood–brain barrier


The blood-brain barrier restricts the diffusion of solutes in the blood (e.g., bacteria) and large or hydrophilic molecules into the cerebrospinal fluid (CSF), while allowing the diffusion of hydrophobic molecules (O2, CO2, hormones) and small polar molecules. Cells of the barrier actively transport metabolicproducts such as glucose across the barrier using specific transport proteins.

Answer 2



The blood–brain barrier is composed of high-density cells restricting passage of substances from the bloodstream much more than do the endothelial cells in capillaries elsewhere in the body. ... Several areas of the human brain are not on the brainside of the BBB