Present in most capillaries, these structures are absent in those of the blood-brain barrier.

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Quizplus · Accepted Answer

Intercellular clefts are present in most capillaries, allowing for the exchange of water, small solutes, and some larger plasma proteins. However, they are absent or significantly reduced in the capillaries of the blood-brain barrier, which is much more selective, allowing only certain substances to pass to maintain a stable environment for the brain.

Present in Most Capillaries, These Structures Are Absent in Those