The Primo Vascular System (PVS) is a network of extremely fine vessels and small nodular structures found throughout the body. It was first reported in the 1960s by North Korean researcher Kim Bonghan, who described a previously unrecognized anatomical system distributed through the tissues and organs, blood and lymphatic vessels, body cavities, and nervous system.
Beginning in the early 2000s, researchers in South Korea and abroad reinvestigated and reproduced many of Kim’s original observations, while making further discoveries using modern microscopy, staining, imaging, and molecular techniques.
What does it look like?
The PVS consists primarily of two structures: primo-vessels and primo-nodes.
Primo-vessels are very fine, translucent, thread-like structures. Unlike an ordinary blood or lymphatic vessel, a primo-vessel contains multiple microscopic channels, or subvessels, running together within it.
At intervals, these vessels connect with slightly larger structures called primo-nodes. Together, the vessels and nodes form pathways and networks extending through different anatomical environments of the body.
Where is it found?
PVS structures have been observed in a remarkable variety of locations: on and within internal organs, inside blood and lymphatic vessels, along nerves, within body cavities, and in connective tissues.
This is one of the unusual features of the system. Rather than being confined to a single anatomical region, the PVS appears to form relationships with many of the body’s other major systems.
What does the PVS do?
Research has associated the PVS with development, tissue growth and repair, immune activity, cell transport, and regeneration. Primo-nodes have been reported to contain several populations of immune and immature or stem-like cells, while the fluid within primo-vessels contains a variety of biological substances.
These findings have led researchers to investigate whether the PVS participates in maintaining, renewing, and restoring tissues, rather than simply transporting blood, lymph, or nerve signals.
Why has it not been seen before?
The PVS is unusually difficult to observe because it appears to be a living, dynamic system. Primo-vessels are extremely fine and translucent, and experimental observations have reported that they diminish markedly under anesthesia and collapse after death. A structure that is apparent in the living state may therefore become extremely difficult to distinguish during conventional anatomical dissection.
The system is also easily overlooked. Its delicate vessels can resemble connective tissue, fibrin strands, or other familiar structures, while many occur in unexpected locations—floating within blood vessels and lymphatics, on organ surfaces, within body cavities, and inside tissues.
For this reason, much modern PVS research has depended upon methods that make the system visible in the living or recently living body. An important breakthrough was the use of dyes and tracers that could enter or preferentially stain primo-vessels, allowing researchers to identify and follow structures that would otherwise be almost invisible.
The PVS may therefore have remained hidden not simply because it is microscopic, but because the conventional methods used to study anatomy can alter or eliminate the very characteristics that make it recognizable.