The blood-brain barrier

Options

A. Consists of both anatomical and physiological factors
B. Regulates to some extent the passage of substances from the blood to the interstitial fluid of the brain
C. Is anatomically related to the formation of tight junctions between adjacent capillary endothelial cells
D. All of the above are correct

Answer

D

Explanation

The blood brain barrier consists mainly of tight junctions that seal together the endothelial cells of brain blood capillaries with processes of astrocytes that surrounds the capillaries.
It regulates the passage of substances from the blood to the interstial fluid of the brain. A few water soluble substances such as glucose, respiratory gases cross the blood brain barrier by active transport other substances such as creatinine, urea and most ions cross the blood brain barrier very slowly. Proteins and most antibiotic drugs do not pass at all from the blood into brain tissue. However, lipid soluble substances such as alcohol are able to access brain tissue freely. Thus blood brain barrier serves a protection to CNS from a variety of harmful chemicals.