CC BY
13
MORPHOFUNCTIONAL PECULIARITIES AND SPACE POSITION OF HEMOMICIRCULATORY VESSELS OF SUPERFICIAL FASCIA OF THE LENGTHENING LIMB
V. I. Shevtsov, Y.M. Iryanov, N.V. Petrovskaya
The hemomicrocirulatory bed of the superficial fascia of canine tibia, after flexion osteoclasia of the tibial bones was studied with electronic microscopy in corrosion injection vascular replicas and coin-pared with that of intact adult animals and 6-8 month old puppies, at three different moments i.e at 5 days, 28 days and 42 days after the operation.
Angioarchitectonics of the superficial fasicia in intact adult dogs is characterized by the presence of triadae, comprising terminal artery and two accompanying parallel veins, which go in different directions, like singular capillares, while in puppies they have mainly longitudinal orientation.
By the time of experiment (33 and 47 days after surgery) a a vascular complex of a typical zigzag shape (fig. 1) is formed in the superficial fascia of the bone regenerate of the lengthening limb. This vascular complex is comprised of:
1) a circular placed terminal artery 60-75 mem in diameter,
2) parallel to the above. Portions of the longitudinal terminal vein 150-200 mem in diameter
3) two circular venules branching off it, 70-1 10 mem in diameter
4) two paraarterial vascular plexi positioned proxi-mally and distally from it.
The latter is surrounded by multiple venous tracts, 6-10 in munber. which is characteristic of tissues under long term tension stress in natural conditions.
Straight arterioles 25-30 mem in diamete; with even contours were branching from the terminal artery every 700-1000 mem i distal and proxima direction at an angle close to 80 degree whic provided good supply to the exchange vessels o microcirculatory bed. Arterioles were placed alonj the tension stress vector strictly in vertical directid and were accompanied by several parallel venulae Multiple arteriol-venular, arteriol-arteriolar an venulo-venular arcade anastomoses from a certaii structure of direct and inverse blood How, thai-reminded a rope ladder at certain areas.
Precapillar arterioles, both parallel and per pendicular to each other, were branching off fror either vertical arterioles or- directly from circula terminal artery (fig. 2 ). Vertical precapillar arteriole were 900-1100 mem in length and were almos twice as long as circular arterioles that were 450 600 mem with almost equal initial diameter of 15-21 mem. The angle between precapillary arterioles am arterioles was 60-80 degrees and was open from th side of the blood flow, while the angulation wa oriented along the hemodynamic gradient, that be ing an important morphofunctional feature, allowed to obtain objective information on directior of blood flow in different parts of arteriolar tract. Examination of our preparations demonstrated thai in vertical arterioles blood moves, not in singl direction (from terminal artery to vertical arterioles), but, due to multiple arteriol-arterioloar anastomose! there was a back blood flow (from aberant arteriole; to the circular artery). There occured a heterogenic distribution ofblood flow, when in the neighbourim arterioles blood flowed in opposite directions wbicl improved the usage of arterial blood, providinj intensive metabolism in the lengthening fascia.
The orientation of the microcirculatory bed of the superficial fascia of the lengthening limb was characterised by recurrent zonal structure-func-tional complexes of microvessels - microcirculatory units (microcirculatory modules), oriented in vertical and circulatory directions.They were rectangular, romboid or polygonal shaped of identical structure, limited by venularand arteriolar trunks (fig.2, They comprise arterioles, precapillary arterioles, precapillares, capillares, postcapillares, postcapillar venules and venules. Vertical microcirculatory complexes had a most complex structure and length equal to precapillar arterioles (up to 1100 mem) which proved vector direction of fascial growth of the lengthening tibia under stimulating influence of tension stress, arised under gradual distraction of bone fragments.
Fifo; 1
The forming microcirculatory modules were of different maturity. In those developing directly near acircular vascular complex close to the longitudinal vein and trunks, coming off it in vertical and circular directions, the microcirculatory bed was almost completely formed which had -a complex 3 D structure. In other modules this process was far from end and they looked like almost half-empty cells limited by venous trunks with an initial stage of microcirculatory bed formation in the corners of the cells (fig. 2).
Precapillar arterioles are the main sourse of microcirculatory modules blood supply. Here they
placed along their longitudinal axis parallel to one of peripheric venulea or diagonally between two venules. Precapillary arterioulesstert 5-6 precapillares which were formed by side or end V-shaped dichotomic branches. This created a dense capillary network with polymorphous loops and were placed mostly longitudinally. Short postcapillary trunks were formed by two capillares and entered into postcapillar venules, bringing blood into venules at the edge of the modules. Thelenght of longitudinal microciailatory modules measured 900-1 100 * 500-600 mem, while circular modules were 450-600 * 200 -300 mem long.
Analysing peculiarities ofincoming blood vessels, that were presented with precapillary arterioles, precapillares and outgoing vessles, formed with a complex of postcapillares, postcapillar and collective venulae, a peculiar structure of microvessels in the modules could be noted. Two separte poles were formed: arteriolar and venular with concentration of the same type of vessels. The arteriolar pole was closer to the circular terminal artery, while the venular pole was situated at the oppsite side. This proved that connection of the modular microvessels was made in accordance with the hemodynamic gradient direction which has mostly a centrifugal direction.
Precapillar arterioles, giving 5-6 precapllares,provided 2- 3 neighboring microcirculatory modules, with blood , giving them in this way additional bloodsupply, alongside with their main source, their own precapillar arterioles.
Precapillares had an initial diameter of about 8-10 mem and they dichotomically separated into two trunks. Each of them made 3-4 capillares by side branching and a couple more by terminal branching. Therefore, One precapillar makes 10-12 caplliares. Since several precapillares took part in blood supply, the total number of capillares in microcirculatory module shaped along the tension stress vector was 20-22.
Each precapillary branched together with its capillaresjoining into a postcapillary. One postcapillary venula formed an elementary working subunit of microcirculatory module. It was possible to reveal 5-6 such subunits 500-600 * 300 mem long in a mature microcirculatory module that had mostly a vertical orientation as the module itself. Despite a certain structural and functional independence, microvascular networks of the elementry sub units were gathered into common vascular system of the module functioning as one unit.
In non-mature microcirculatory modules 600-700 mem laterally and medially of the central longitudinal vein (fig. 2) local working subunits had rather simple structure and were not connected with each other. Blood came to them from thin precapillares, oriented at 40-60 degrees, or at a right angle to the tension stress vector, formed after side or terminal branching of an arteriole. One forming working subunit containedbesideprecapillare, 1-2 parallel postcapillar venules 100-250 mem of the length, which had the shape of a bush or a chandellier, oriented along the tension stress vector, 2-3 postcapillares entered them and short growing capillar terminates, had no ties with each other, nor a strict orientation.
It is to be noted that newly forming capillar terminales started mainly from venular vessels of the microcirculatory bed of the developing local subunits, while the growing arteriolar terminals spreaded over considerable distance without branching into capillares; only after 3-4 generations ofdichotonic branching they became thinner, forming a long straight arteriolar-venular passage where a capillar can be distinguished only by its rather thick venular end.
Microcirculatory modules, formed by precapillar arterioles and venulae with circular orientation, and perpendicular to the tension stress vector, were characterized by concentrated vascular elements with considerably greater number of venules compared to the number of arterioles, a large number of
venulo-venular and arterio-venular anestomoses which demonstrated a sideways circulation. A part of precapillares coming directly into postcapillar and collective venulae provide rapid circulation. The cells of the formed vascular network had an almost rectangular shape and were perpendicular to the tension stress vector. Major capillaries in the modules are mostly vertical as the venulo-venular anastomoses were, while nutrient ones formed rectangular cells around vertical arteriolar and venular
trunks, enveloping them in circles. Fn-
In the part of the circular vascular complex between the terminal artery and large longitudinal venous trunks, the microcirculatory modules were formed mainly from two working subunits, supplied with blood by one precapillary arteriole (fig. I)). The latter was separated into two branches each of them started 2-3 nutrient capillares 160-200 mem long forming longitudnal and perpendicular closed ellypsoid cells, neighboring local subunits of which were connected through long communication capillares 400-500 mem long. The capillares enter short postcapillar venules, or directly, collective venules, frequently forming closed round circular structures gathering into two parallel veins, accompanying the artery.
Proximally and distally from the circular terminal artery there was a dense vascular network of paraateriolar junctions with multiple venous vessels
(fig.l). They were represented by large T-shape branching venulae, anastomosing with vertical and circular trunks, and also, by multiple collective and postcapillar venulae placed along the circular arterial surface. Bloodsupply of paraarterial vascular junctions was provided through precapillar arterioles, which branched off vertical terminal arterioles and dichotonically separated into capillares, while modular structure of the micricirculatory bed of paraarterial junction was not clearly marked. Each branch of precapillar arteriol started 6-8 capillares that were mostly of the major group, and formed circular arterio-venular passages that acted as additional collatérales.
vertical arterioles accompained by venulae (arrow). A paraaterial vascular junction formed by multiple venous trunks is situated at both sides of the terminal artery. 42nd day of distraction, magnification 45.
Fig.2. Longitudinal structural functional microvascular complexes (microcirculatory modules); a mature (horizontal arrow) and a forming (vertical arrow) ones. 42nd day of distration. Magnification 45.
Therefore, the studies conducted have demonstrated a number of peculiarities of angioarchitectonics of the superficial fascia of the lengthening tibia, which to our opinion, proves active vasculogenesis, especially marked in the venular part of microcirculatory bed which acquires greater volume and length compared to the arterial one. Largest in numbers are venous vessels in paraaterial vascular junctions, shaped around the terminal circular artery. Such vascular complexes are described by a number of authors in different tissue types, e.g. in the tail offlipper of dolphin (A G. Tomilin, 195 1; V. V. Kuprianov, 1993), in abdomen (J. L Karaganov, V. V. Banin, 1973), in mesentery (V. P. Tutatchikov, 1983), in serous cover of rectum (R. J. Krasnay, 1884), in pericardium (I. U Yuldashev, 1986) and in tissue under long term natural tension stress. Angiogenesis in the superficial fascia of the lengthening tibia is accompained with formation of new structural and functional microvascular complexes. Microcirculatory modules of longitudinal and circular orientation. Modules that proivide vector type growth of fascia under stimulating influence of tension stress have the greatest length.
Lengends for figures
Fig. 1. Circular vascular complex forming at the level of distractional bone regenerate in the superficial fascia of the lengthening tibia. Straigth
Literature
1. Tomilin A. G. Termoregulation in whales. Priroda, 1951, No. 6 pp 55-53.
2. V. V. Kuprianous Microvascular network in tail and tail flippers in dolphins. Archiv anatomii, i embriologii. 1983, no 12, pp 42-50.
3. J.L. Karaganov, V. V. Banin. Topological principle in the study of structural functional microcirculatory units Archiv anatomii, gistologii i embriologii. 1978, No. 11, pp 5-22.
4. V. P. Tutatchiikov. Change in microcirculatory bed and hypercholisterenemy. Archive anatomii, gistologii i embriologii. 1983, No. 12, pp 51-57.
5. R J. Krasny. Microarchitectoincs and microtopography of human rectal vessels.. Archiv anatomii, gistologii i embriologii. 1984, No 4, pp 26-34.
6. I. U. Yuldashev. Morphofunctional charactersitics of hemomicrocirculatory bed of canine pericardium. Archiv anatomii, gistologii i embriologii. 1986, No 7, pp 43-48.
