Capillary blood vessel

“ Venous bleeding (from a vein) occurs as a steady even stream of dark blood, not affected by the heart beat.
(c) Capillary hemorrhage is in the form of a steady stream oozing from the raw surface of a tissue. The color is intermediary, as both arterial and venous capillaries contribute to it.
Nature’s Efforts to Control Hemorrhage. When an [Pg 52] artery is severed, the inner and middle coats immediately retract and curl up within the lumen, partially closing up the cut end. ”

“ The only way in which it is possible to cure this disease is, to produce an obliteration of the cavity of the artery. This is the object of the operation. The diseased artery is exposed, and a ligature is passed around it, above the dilatation, by means of which the blood is prevented from flowing into the sac, and inflammation is excited in the vessel; in consequence of which its sides adhere together, and its cavity becomes obliterated. The success of the operation depends entirely on the completeness of the adhesion of the sides of the vessel, and the consequent obliteration of its cavity. ”

“ The rider assumes legs extending into the arterial branches beyond the place of obstruction, and a body which extends backward in the course of the circulation to the nearest branch. The result of the total obstruction of the vessel is to cut off the admission of arterial blood, producing a local anæmia. The contraction of the elastic tissues of the part propels toward the capillaries a certain quantity of the blood in the vessels beyond the point of obstruction, till this force becomes neutralized by the blood-pressure in the vessels surrounding the obstructed region. ”

“ It is so, because it has been obtained from the capillary arteries, which in this case being empty received blood by regurgitation from the veins, the valves of which when present do not prevent its reflux course. If a limb be injected and carefully dissected four or five days after a ligature has been placed during life high up on the principal trunk, the capillary vessels will be seen to be well injected; but few or none will be found large enough to admit of their inosculation being traced throughout. ”

“ The coats of the external jugular vein, E, Plate 3, are said to hold connexion with some of the fibres of the platysma-myoides muscle, A A, Plate 3, and that therefore, if the vessel be divided transversely, the two orifices will remain patent for a time.
The position of the carotid artery protects the vessel, in some degree, against the suicidal act, as generally attempted. The depth of the incision necessary to reach the main blood-vessels from the fore part of the neck is so considerable that the wound seldom effects more than the opening of some part of the larynx. ”

“ All over the body there are, though you can not see them, networks of capillaries. All the arteries end in capillaries, and in them begin all veins. Supposing a little blood-corpuscle be squeezed in the narrow pathway of a capillary in the muscle of the arm. ”

“ Although in most instances the organs of the body are supplied with arterialised blood conveyed to them by arteries, there are nevertheless cases in which an organ may receive venous blood by a vein in addition to arterial blood supplied by an artery. For example, the capillaries of the liver not only receive blood from the hepatic artery, but also venous blood by a large vein (hepatic portal vein) , formed by the union of a number of smaller veins by which venous blood is collected from the capillaries of the stomach, intestine, spleen, and pancreas. ”

“ If the absorption of the terminations of the veins is not equally impaired with the force of the heart and arteries, the blood is taken up by the veins the instant it arrives at their extremities; the capillary vessels are left empty, and there is less resistance to the current of the blood from the arteries; hence the pulse becomes empty, as well as weak and quick; the veins of the skin are fuller than the arteries of it ”

“ The vascular system itself is quite peculiar, consisting of lacunae and channels destitute of endothelium, situated within the thickness of the basement-membrane of the body-wall, of the gut-wall and of the mesenteries. The blood, which is a non-corpuscular fluid, is propelled forwards by the contractile dorsal vessel and collected into the central blood-sinus; this lies over the stomochord, and is surrounded on three sides by a closed vesicle, with contractile walls, called the pericardium (Herzblase) . ”

“ A very interesting observation which I made long ago, but to which I have not before directed attention in this point of view, shows that an extreme degree of adhesiveness of the red discs may exist within a blood-vessel the walls of which are in perfect health with reference to coagulation. If a horse's jugular vein, obtained in the manner I have described, is suspended vertically, the blood in it remains fluid for an indefinite period, hut the red corpuscles soon fall from the upper parts of the fluid, leaving a huffy layer of plasma, readily seen through the translucent wall of the vessel. ”

“ In arterial hæmorrhage the blood is bright red in colour, and escapes from the cardiac end of the divided vessel in pulsating jets synchronously with the systole of the heart. In vascular parts—for example the face—both ends of a divided artery bleed freely. The blood flowing from an artery may be dark in colour if the respiration is impeded. When the heart's action is weak and the blood tension low the flow may appear to be continuous and not in jets. The blood from a divided artery at the bottom of a deep wound, escapes on the surface in a steady flow. ”

“ Extensive effusions of serum, lymph, and pus, mixed in different proportions, will take place in the serous cavities of the body, and become infiltrated in the cellular membrane, accompanied with very slight indications of inflammatory action. The colouring matter of the blood will also sometimes become effused with its other parts; but when this is the case, the blood will be found to have lost its coagulating power: in this respect presenting a direct contrast to the effusion from a healthy wounded vessel. ”

“ If an artery is only _partly cut across_, the divided fibres of the tunica muscularis contract and those of the tunica externa retract, with the result that a more or less circular hole is formed in the wall of the vessel, from which free bleeding takes place, as the conditions are unfavourable for the formation of an occluding clot. Even if a clot does form, when the blood-pressure rises it is readily displaced, leading to reactionary haemorrhage. Should the wound become infected, secondary haemorrhage is specially liable to occur. ”

“ The lungs did not readily collapse when the chest was opened. The auricles of the heart were greatly distended with black blood; the inner surface of the left ventricle presented a white patch, of about two square inches in extent; the lining membrane of the aorta, for several inches, was of a bright red colour; this extended round one-third only of the circumference of the vessel. No other structural change could be found in the heart or vessels, which would account for the symptoms observed during life. ”

“ The arteries, commencing in the great trunk of the aorta, branch off into large and then into smaller tubes, until they form capillary or hair-like vessels, penetrating everywhere.
[Pg 212]
"As for man his days are as grass; as a flower of the field so he flourisheth."—Psalm ciii.
The capillary extremities of the arteries, unite with the capillary extremities of the veins, and the blood passes from the one set of vessels into the other. As the arteries become smaller from the point where they receive the blood, so the veins grow larger ”

“ The examination of the blood, or of the vessels, in such cases, will by no means invariably indicate the presence of foreign matter after it has once become thoroughly mixed with the blood, nor will inflammation of the vein through which the fluid passes, be by any means invariably produced.
When a foreign substance is introduced into an artery, any immediate effects upon the blood may naturally be looked for in the system of capillaries which it supplies. If the blood then coagulates, local symptoms alone, will, in the first instance, be produced, and the constitution will remain unaffected. ”

“ A sufficiency of blood to distend it collects within the venous cistern. The arterial system, owin to its elasticity and contractility, empties. If the heart now begin to beat, blood is taken from the venous system and is driven into the arterial system., The arteries receive more blood than can escape through the capillary vessels, and the arterial side of the system becomes distended, until equilibrium is reached, and as much blood escapes into the venous side per unit of time as is delivered by the heart. ”

“ The patches of congestion, so characteristic of this disease in other organs, are not here observed. This may depend upon the peculiar disposition of the capillary system of the kidney. The blood has to pass through the Malpigian tufts, and may be purified, or altered in character, before it reaches the proper venous system of the organ.
In cases where purulent infection of the blood has been purposely produced, portions of the kidney will not unfrequently be found inflamed and firmer than natural ”

“ In many cases, if the exciting cause is removed, nothing more is required; the inflammation speedily subsides. If the cause cannot be removed, or if, after its removal, the inflammation proceeds unabated, the arterial action must be reduced by general and local abstraction of blood. By general depletion, the action of the whole sanguiferous system is diminished, as well as of those vessels more immediately engaged in the morbid action; but the affected capillaries are still dilated, and less capable than the larger trunks of effective contraction to propel their contents ”

“ The dilatation of arteries, more especially of the internal ones, is often very great; ultimately the internal coat gives way, and the external, with the surrounding tissues, yields in proportion as the blood diffuses itself. The internal tunic is occasionally burst in consequence of violent and sudden muscular exertion; and, even when the vessels are pretty limber and sound, effusion of lymph, and obliteration of the vessel ensue, or, more frequently, aneurism. ”

“ Ligature of the aorta may result in either an increased or decreased flow of direct lymph. One explanation of these results has been offered from a study of the changes in capillary pressure set up in the main organs involved. Thus, after ligature of the portal vein the capillary pressure in the intestines rises, and it was proved that the increase in thoracic duct lymph came from the intestines. Ligaturing the inferior vena cava causes a big rise in the pressure in the liver capillaries, the intestinal capillary pressure remaining practically unaltered. ”

“ Thrombosis—clotting in the vessel. Embolism, blocking of the vessel. Thrombus may form in any bloodvessel. Embolism occurs in arteries. Clot follows the blood current. Causes of clotting—fibrinogen, paraglobulin, fibrine ferment; foreign bodies; parasites; air; blood that has been exposed, transfusion; ærial germs; disease germs; chemical coagulants; high and low temperatures; breaches of endothelium; congestion or inflammation of the serosa; stasis of blood and extension of clot; ligature near a branch vessel: deoxidation and carbonization of blood, marasmus; neoplasms ”

“ When the hand is cold the arterioles are so constricted that blood only passes through the wider and more direct capillaries. As the skin becomes warm it flushes, the arterioles dilating and all the capillary networks becoming filled with blood. Muscular movements express the blood out of the capillaries, as may be seen by the blanching of the skin which occurs on clenching the hand. ”

“ There is also venous engorgement of the brain, spinal cord, and lungs. Ecchymoses and extravasations of blood are found in the skin and mucous membranes.
Treatment.—Drain blood from a large vein during the injection. The first two bottles of the injection should be of half strength fluid. The face should be massaged to assist in the securing of capillary circulation and in the elimination of the blood discoloration. The body should be treated as soon as possible after death, as putrefaction begins early. ”

“ In the close of malignant fevers, where bleeding has been omitted in the beginning of the disease, blood drawn from a vein is generally so dissolved, as to be beyond the reach of repeated bleedings to restore it to its natural texture. In this case, arteriotomy might probably be performed with advantage. The arteries, which retain their capacity of life longer than the veins, by being relieved from the immediate pressure of blood upon them, might be enabled so to act upon the torpid veins, as to restore their natural action, and thereby to arrest departing life. ”

“ Hypertrophy of the intimal cells takes place, layer upon layer being added in an attempt to strengthen the vessel at the injured place. Coincidently with this, there is thickening by a connective tissue growth in the adventitia. The process begins, at least in syphilis, around the terminals of the vasa vasorum. It will be recalled that the blood supply of the inner portion of the media comes [38] from within the vessel itself. As the intimal growth increases, the blood supply is cut off. The inevitable result is softening of the portion farthest from the lumen of the vessel. ”