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Continuous capillaries of the brain differ from other continuous capillaries in which way?
AThey carry lymph rather than blood plasma
BThey lack intercellular clefts and add astrocyte end feet
CThey gain fenestrations across the whole endothelium
DThey lose their basement membrane entirely here
Answer & Solution
Correct answer: B. They lack intercellular clefts and add astrocyte end feet
1. A typical continuous capillary has tight junctions that are often incomplete, leaving intercellular clefts.
2. Those clefts let water and small molecules cross between blood and interstitial fluid.
3. Brain continuous capillaries have no such clefts, add a thick basement membrane and are wrapped by astrocyte end feet.
4. Together these features form the blood brain barrier and stop nearly all substances crossing.
5. The basement membrane there is thicker rather than absent, and lymph is carried by sinusoids of lymph nodes.
_Source: OpenStax Anatomy and Physiology (CC BY 4.0), Ch 20 "The Cardiovascular System: Blood Vessels and Circulation", section 20.1 Structure and Function of Blood Vessels_
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