Blood-brain barrier refers to a highly selective and protective physiological mechanism found within the central nervous system (CNS), particularly the brain, that acts as a barrier to prevent the unregulated entry of various substances and pathogens from the bloodstream into the brain tissue. It is a specialized structure formed by a tightly packed network of endothelial cells lining the blood vessels in the brain.
The primary function of the blood-brain barrier is to maintain homeostasis and protect the brain from potentially harmful or toxic substances circulating in the blood. It achieves this by tightly regulating the passage of molecules between the bloodstream and the brain tissue. The barrier is highly selective and only allows essential nutrients, such as glucose and amino acids, to enter the brain, while restricting the entry of large molecules, toxins, and most pathogens.
The blood-brain barrier is formed by a combination of physical, chemical, and cellular mechanisms. The endothelial cells lining the blood vessels in the brain are connected by tight junctions, which prevent the leakage of molecules between the cells. Additionally, specialized transport proteins and enzymes help actively transport necessary molecules across the barrier, while efflux transporters remove potentially harmful substances from the brain tissue.
Disruption or dysfunction of the blood-brain barrier can occur in various pathological conditions, such as infections, inflammation, tumors, or neurodegenerative diseases. Such impairment can allow the entry of harmful substances into the brain, leading to damage or dysfunction of the central nervous system. Consequently, understanding the blood-brain barrier's structure and function is vital for developing diagnostic tools and targeted therapies to treat disorders of the CNS.
