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. Author manuscript; available in PMC: 2022 Aug 1.
Published in final edited form as: Drug Deliv Transl Res. 2021 Oct 30;11(6):2448–2467. doi: 10.1007/s13346-021-01079-1

Figure 1: Barriers in the brain.

Figure 1:

A) The blood brain barrier (BBB) is a diffusion barrier that impedes the entrance of substances from the blood to the brain to maintain brain homeostasis B) The blood-cerebrospinal fluid barrier is formed by modified epithelial cells. It is located between the choroid plexus and the arachnoid membrane. C) Abnormal angiogenesis in tumors occurs due to an overproduction of proangiogenic factors. This leads to the formation of blood vessels that lack a normal physiological structure. Combined with heightened intratumoral pressure, this barrier is a unique impediment to drug delivery