Some observations on the course of arteries: a study of arterial patterns in man, as exemplified in the placenta, the pulmonary and bronchial arteries, the arteries of the intestine and of skeletal muscle, demonstrating the fundamental relationship between the course of arteries and the function of the organs they supply

Abstract

A preliminary discussion about the course of arteries with particular reference to anastomoses and end-arteries, and with some observations based on Hilton's work, introduced this investigation. Some of the literature was briefly reviewed, and the different views by different authorities, especially in regard to the vessels of the intestine were discussed.

The arteries of certain regions were then selected for study with a view to seeing if there was any particular association of the form of the vessels with the function of the organ they supplied. For that reason the arteries of 1. The placenta, 2. the pulmonary bronchial arteries, 3. the intestinal arteries, 4. the arteries of skeletal muscle were studied.

Various methods of demonstrating the course of arteries were employed;

1. The celloidin corrosion cast technique, of which a description is given. It was found to be satisfactory for the placenta, an ideal organ for injection as, owing to the arrangement of vessels as a series of end arteries, the leakage is minimal and hence a good cast assured. The use of different coloured celloidins, stained red for one umbilical artery, stained blue for the other,' was satisfactory in determining if any peripheral anastomoses were present between the two arteries.

The celloidin cast technique, using two different coloured celloidin solutions was equally satisfactory in determining if there were any macroscopic junctions between the pulmonary and the bronchial arteries.

The celloidin corrosion technique was particularly suitable in specimens of the intestine, as these thin tissues were easily corroded in acid, and the casts leant themselves readily to photography. It was not so satisfactory in specimens of skeletal muscle especially in the foetus; once the soft tissues were corroded it was difficult to estimate where exactly the vessels had been situated, even with the corresponding limb of the opposite side injected with starch and red lead and dissected as a control.

2. Injection with starch and red lead and dissection proved a useful method for demonstrating the course of arteries in skeletal muscle.

3. Injection with a preparation of vermilion and then X-raying was not very successful either in the placenta or in skeletal muscle owing perhaps to the failure in preparing the injection material correctly.

4. Injection with starch red lead and barium sulphate and then X-raying proved satisfactory for demonstrating the vessels in skeletal muscle.

The experimental work was divided into four sections:

1. The placental vessels 2. The pulmonary bronchial vessels 3. The intestinal vessels 4. The vessels of muscles.

In each section a preliminary discussion on the results of previous workers preceded the records of the experiments performed, and was concluded by review of the facts observed. 23 photographs and 59 drawings illustrated the results obtained.

From a review of the experiments performed, the conclusion was drawn that there is a very close relationship between the course of the vessels and the function of the organs they supply. The observation that the course of arteries is always protected as far as possible, was repeatedly demonstrated in these experiments. Especially was this so in relation to the arteries supplying muscles. Muscles of similar form have a similar pattern of blood vessels. The vessels which go to a muscle do not traverse a contractile element (another muscle) first which would act as a living ligature, unless the muscle they traverse is part of the muscle they are going to supply. No vessels were seen traversing muscles of a different structure and function to the one they were going to supply.

The relation of the course of arteries to the movements of the organs they supply was demonstrated. The anastomotic channel between the two umbilical arteries as they enter the placenta, the constant anastomotic arcade across the bifurcation of the main arteries of the colon, the anastomotic loops between the nutrient vessels entering the quadrilateral and fusiform muscles are all designed with the similar purpose of regulating the flow through them as the wave of contraction passes along the region they supply. The arterial patterns are, in fact, intimately related with the movements of the organs they supply. In the more fixed parts of the colon there is a straight margina artery with the versa recta coming off it.Wien an are is reached where there is more mobility, i.e. the pelvic colon, arcade formation starts in the pelvic mesocolon, similar, though not as complicated as in the mesentery of the small intestine, also a mobile organ. The vessels on the intestine walls are not mainly longitudinal channels in which a concertina like effect would be produced on them when waves of peristalsis pass down the intestine but are in line with the circular muscle of the intestine, as a series of vascular rings. This arrangement also suits the venous return, the veins having the same course as the arteries.

The blood supply to sartorius is also comparable with this - not one long vessel arising at the to and running down in the contractile element of the muscle from origin to insertion but a series of vessels entering all the way down with the finer subdivisions running parallel with the muscle fibres.

Anastomoses are not haphazard affairs, The constant presence of an anastomic channel across the bifurcation of an artery, in the vessels of the intestine, was noted inall the specimens examined. No specific search was made for Sudeck's "critical point ", a point on the pelvic colon where the vascular supply is stated to be especially precarious on account of the poor anastomosis between the superior haemorrhoidal and the lowest sigmoid artery. But in the specimens of colon examined (Nos. 4, 9, 13, 14, 15a, 16, 17, 24) which included that area of the intestine, the arcade produced by an anastomotic channel across the bifurcation between superior haemorrhoidal and last sigmoid artery was similar to those between the othef sigmoid arteries. There is no reason why there should not be this anastomosis - the absence of an anastomosis would be contrary to the usual formation, and certainly in these experiments Sudeck's point was not present.

?in anastomosic channel between the peripheral ends of the umbilical arteries would be in a precarious position, constantly occluded by the waves of contraction passing over the uterus, and also hindering the regular and orderly thrombosis in the vessels of the cotyledons when the placenta separates, which are specially designed as end arteries to produce this effect. No such channel was present in any of the specimens injected in the present investigation. Similarly there is no anastomosis of arterial size between the pulmonary and bronchial arteries. These vessels have very different functions, and a free anastomosis between them is therefore not normally required. No such anastomosis was demonstrated.

Some facts, as described by previous investigators were confirmed, while with others different results were obtained. In brief these may be summarised as follows:-

1. The findings regarding the placental vessels were the same as those of Bacsich and Smout, as I have described in the section on the placenta, viz, the presence of a communicating channel between the two umbilical arteries, as they enter the placenta, and no anastomoses thereafter.

2. The absence of arterial anastomosis between the pulmonary and bronchial arteries, was confirmed. This result concurs with the work of Daly and W.S. Miller.

3. A free anastomosis was found between the vasa recta of the small intestine, on the intestinal wall and between vasa recta of opposite sides on the antimesenteric border. This confirms the findings of Foer, and is different to the older observations of Cokkinis, who found no such anastomoses.

4. The loop formation of the vasa recta on the base of appendices epiploicae, as described by PeilleOr.e, was not observed in any of the 26 colons examined. Experiments were performed in tying the base of several appetdices epiploicae prior to injection, to see if these affected the vasa longa; but in every case the injection material flowed on beyond the level of the ligature.

5. A different approach to other investigations was taken in the study of the vascular supply to skeletal muscle, Some muscles were taken according to their classification by the arrangement of their component fibres and the arterial pattern in individual muscles from different parts of the body belonging to the same group were compared.

The arterial supply of muscles was classed as (1) major (2) minor supply. Four varieties of arterial pattern were distinguished, not five as Blomfield has described them. It was considered that the distinction of the anastomosis between entering vessels in certain muscles, either as a longitudinal channel or as a series of loops, into two separate groups was an unnecessary elaboration.

The two specimens of adult limbs had been amputated for conditions which were not considered to have affected the vascular patterns, and the results obtained were considered to demonstrate a more or less normal appearance, and could be used to compare with those of a limb removed for vascular disease. The present investigation was an enquiry into normal appearances. Hence several limbs amputated for senile gangrene, though available were not utilised as the appearances they would have shown could not have demonstrated what was desired, the normal pattern.

A number of variations. were noted especially in the origins of the vasa recta of the colon, some arising singly, some arising as a pair off a common stem and going to the same or to opposite sides of the intestine. But these are minor variatións, and the essential underlying pattern - straight vessels passing at right angles to. the long axis of the colon with any given area of colon wall getting approximately the same supply as another similar area was the same, whatever the origin of the feeding arteries may have been. The same applies to the origin of vessels off an "axis" artery in the limbs - the superficial epigastric, circumflex and external pudendal arteries coming off the profunda femoris for example, as noted on one cadaver recently, is merely a variant and is perfectly normal. Such alternate patterns to those more usually described should be remembered, however, and students weaned of the idea that they are "abnormal ". In preference the term "variation" should be employed.

One must accept the "dynamic view" of the vascular system, as Woo ,rd (1922) has described it "The vascular net depends upon the inherent properties of certain cells to form blood vessels and blood cells, these properties being regulated by the needs and activities of the surrounding tissues ". There is nothing haphazard or irregular about it. "Function determines form "; and in the end arteries of the placenta, the rich vascularity.of the small intestine with its freely communicating arterial rings, and the other examples described in the previous pages, this law is displayed.