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Table 1 Types of blood vessels in various organs with different permeability

From: Regulation of blood vascular permeability in the skin

A. Charge barrier [17,18,19,20,21,22,23]

Glycocalyx layer

Anionic mesh-like layer with regular spacing of <20 nm for continuous and fenestrated vessels (irregularly found on sinusoidal vessels), on both the surface of IEJ clefts and endothelial cells.

B. Size barrier (reviewed in [2])

Types of blood vessels

Types of endothelial cells

Interendothelial junctions (IEJs)

Representative organs

Estimated upper limit for paracellular transportation [4]

Continuous(non-fenestrated)

Continuous basement membrane

No fenestrae

Tight junctions and adherens junctions

Retina [2] brain, spinal cord [66] thymus [67]

Determined by IEJs (TJs) <1 nm

Adherens junctions with limited contribution of tight junctions

skin [12, 13] muscle, heart [68, 69] adipose tissue [70] lung [71, 72]

Determined by IEJs (AJs) <5 nm

Fenestrated

Fenestrated (with diaphragm)

skin [12, 13]

exocrine glands [73]

kidney (peritubular) [74]

endocrine glands [73, 75, 76]

intestinal mucosa [77, 78]

lymph node [79, 80]

Determined by diaphragm

<6–12 nm [81]

Fenestrated (open pores without diaphragm)

Kidney (glomerulus) [82, 83]

Determined by glycocalyx

<15 nm [2, 19]

Sinusoidal (discontinuous)

Discontinuous basement membrane

Fenestrated (with and/or without diaphragm)

Liver [84,85,86]

spleen [87]

<50–280 nm, largely differ among species

<3–5 μm