Blood brain barrier

Blood-brain barrier (pronunciation: /blʌd breɪn ˈbærɪər/) is a highly selective semipermeable border of endothelial cells that prevents solutes in the circulating blood from non-selectively crossing into the central nervous system (CNS). The blood-brain barrier is formed by brain endothelial cells, which are connected by tight junctions.

Etymology

The term "blood-brain barrier" was coined by the German physician Paul Ehrlich in the late 19th century. The term "barrier" refers to the function of the structure, which is to prevent or slow down the passage of substances from the blood into the brain.

Structure

The blood-brain barrier is composed of high-density cells restricting passage of substances from the bloodstream much more than endothelial cells in capillaries elsewhere in the body. This barrier also includes a thick basement membrane and astrocytic endfeet.

Function

The blood-brain barrier 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. Furthermore, it prevents the entry of lipophilic potential neurotoxins by way of an active transport mechanism mediated by P-glycoprotein.

Clinical significance

Disruption of the blood-brain barrier can result in a number of medical conditions, including meningitis and multiple sclerosis. Certain drugs can also affect the function of the blood-brain barrier, either by disrupting its structure or by blocking the transport mechanisms that allow substances to pass through it.

Related terms

• Endothelial cells
• Central nervous system
• Tight junctions
• Paul Ehrlich
• Meningitis
• Multiple sclerosis

External links

• Medical encyclopedia article on Blood brain barrier
• Wikipedia's article - Blood brain barrier

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