Observation of Coiled Blood Plexus in Rat Skin with Diffusive Light Illumination

Schematic illustration of the optical system for observation of blood vessels in the skin.

Morphology and anatomical distribution of the neurovascular bundles (NBs) and plexuses at K-meridians. (A) Two coiled NBs (arrow) at acupuncture points K15 are seen in subcutaneous connective tissue layer. (B) Magnified image of the rectangular area in Figure 2A shows coiled morphology of the NB (arrow). (C) NBs (arrow) in the stretched state are located at a distance of 9 mm from each other. (s) - skin; (me) - middle epigastrium; (k) - kidney meridian. (D) NBs (arrow) are symmetrically located on both sides of K-meridians. A distance from the middle of the epigastrium (me) to NB is about 4 μm. (E) NB (arrow) forms several branches of blood vessels (arrowhead) in the subcutaneous layer. (F) Large view of the anatomical distribution of the NBs (arrow) along K-meridians on the abdominal side. (u) - umbilicus. Scale bars = 2 mm in A, C, D and E, 1 mm in B.

Relationship of the neurovascular bundles (NBs) and the acupuncture points (APs) on Kidney and Stomach meridian in a rat. (A) Schematic illustration showing the locations of APs in a human. (B) Distribution of the NBs and mapped APs on K- and ST-meridians in the rat. Note that the points K14 to K16 (grey circle) exactly match to the locations of the NBs. The points K17 to K21 and ST20, ST21 (black circle) are located near the NBs (white circle).

Imaging of blood vessel bundles at acupuncture points with diffusive illumination method. (A, C) without and (B, D) with application of saline injection. Arrow and arrowhead indicate blood vessel bundle and branches of blood vessels respectively.

Intra-peritoneal saline injection. Blood vessels on the skin surface and the blood plexus leading into the muscle layer were imaged in vivid contrast. ‘Head’ of the blood plexus and the diversification of blood vessels on the head was also imaged with improved contrast.

The blood plexus and the acupuncture muscle fascicle. (A) The tail part of the blood vessels entered the body muscle layer through the perforation (arrow) in the fascia. The fascia had a criss-cross structure of fibers. (B) The staining dye chrome-hematoxylin flowed in the channel of muscle fascicle (arrowhead) along the K-line, and the dye flowed out through the perforation (arrow).

A schematic illustration of neurovascular plexuses of coiled blood vessels along the kidney meridian (K) and stomach meridian (ST) which are 4–5 mm and 2 cm off from the conception vessel (CV) of a rat. Notice that other neurovascular bundles between the K and ST are straight and not coiled at all.

Anatomical location and immunofluorescence imaging of the neurovascular plexuses in the rat abdomen. (A) Histological thick section of tissue explants including the skin (s), subcutaneous tissue layer (st) and abdominal wall muscle (am) shows that neurovascular plexuses are located under skin about 4 mm away from the middle epigastrium or conception vessel (dashed line). (B and C) Immunofluorescence imaging of the rectangular area of A showing the distribution of the nerve fibers, blood and lymphatic vessels in the neurovascular plexus. Cell nuclei (blue) are stained by DAPI.

Distribution and morphometric characteristics of the neurovascular plexuses. (A) Stereomicroscopic image (Z-plane section) showing two neurovascular plexuses which are located about 4 mm off from the middle epigastrium (dashed line). The distance between the plexuses is about 5 μm. A diameter of the plexus is about 2 μm. (B) Confocal image of the neurovascular plexus indicated by the arrow in A showing a complex network of blood vessels and capillaries (green) around nerve fibers (red). Blood vessels and nerve fibers were stained with RECA-1 and NF-150 kD respectively. Scale bar, 200 μm.

A transversal section image of a neurovascular section in the ST-meridian. (A) blood vessels (B) nerves (C) merged. It clearly revealed the position of the plexus under the skin skeletal muscle (arrow) and above the abdominal muscle layer (⋆).

The image showing nuclei distribution revealed by DAPI staining in the same tissue as shown in Figure 10. The marked region (open arrow) is the neurovascular plexus.