Collateral circulation. Anastomosis. Collateral. Collateral circulation in the brain What are collateral arteries
Collateral circulation is an important functional adaptation of the body associated with the great plasticity of blood vessels and ensuring uninterrupted blood supply to organs and tissues. A deep study of it, which has important practical significance, is associated with the name of V. N. Tonkov and his school
Collateral circulation means lateral, roundabout flow of blood through the lateral vessels. It occurs under physiological conditions during temporary difficulties in blood flow (for example, when blood vessels are compressed in places of movement, in joints). It can also occur in pathological conditions during blockages, wounds, ligation of blood vessels during operations, etc.
Under physiological conditions, roundabout blood flow occurs through lateral anastomoses running parallel to the main ones. These lateral vessels are called collaterals (for example, a. collateralis ulnaris, etc.), hence the name of the blood flow “roundabout”, or collateral circulation.
When there is difficulty in blood flow through the main vessels, caused by their blockage, damage or ligation during operations, blood rushes through anastomoses into the nearest lateral vessels, which expand and become tortuous, their vascular wall is rebuilt due to changes in the muscular layer and elastic frame and they are gradually transformed into collaterals different structure than normal.
Thus, collaterals exist under normal conditions and can develop again in the presence of anastomoses. Consequently, in case of a disorder of normal blood circulation caused by an obstacle to the blood flow in a given vessel, the existing bypass blood paths - collaterals - are first turned on, and then new ones develop. As a result, impaired blood circulation is restored. The nervous system plays an important role in this process.
From the above it follows that it is necessary to clearly define difference between anastomoses and collaterals.
Anastomosis (from the Greek anastomos - I supply the mouth)- anastomosis, every third vessel that connects two others; This is an anatomical concept.
Collateral (from Latin collateralis - lateral)- a lateral vessel that carries out a roundabout flow of blood; This concept is anatomical and physiological.
There are two types of collaterals. Some exist normally and have the structure of a normal vessel, like an anastomosis. Others develop again from anastomoses and acquire a special structure.
To understand collateral circulation it is necessary to know those anastomoses that connect the systems of various vessels, through which collateral blood flow is established in the event of vascular injuries, ligations during operations and blockages (thrombosis and embolism).
Anastomoses between branches of major arterial highways, supplying the main parts of the body (aorta, carotid arteries, subclavian, iliac, etc.) and representing, as it were, separate vascular systems, are called intersystem. Anastomoses between the branches of one large arterial line, limited to the limits of its branching, are called intrasystemic. These anastomoses have already been noted in the course of the presentation of the arteries.
There are anastomoses between the thinnest intraorgan arteries and veins - arteriovenous anastomoses. Through them, blood flows bypassing the microcirculatory bed when it is overfilled and, thus, forms a collateral path that directly connects the arteries and veins, bypassing the capillaries.
In addition, thin arteries and veins take part in the collateral circulation, accompanying the main vessels in the neurovascular bundles and constituting the so-called perivascular and perivascular arterial and venous beds.
Anastomoses, in addition to their practical significance, they are an expression of the unity of the arterial system, which, for ease of study, we artificially divide into separate parts.
Collateral circulation - an important functional adaptation of the body, associated with the great plasticity of blood vessels and ensuring uninterrupted blood supply to organs and tissues.
Collateral circulation refers to the lateral, roundabout flow of blood through the lateral vessels. It occurs under physiological conditions during temporary difficulties in blood flow (for example, when blood vessels are compressed in places of movement, in joints). It can also occur in pathological conditions during blockages, wounds, ligation of blood vessels during operations, etc.
Under physiological conditions, roundabout blood flow occurs through lateral anastomoses running parallel to the main ones. These side vessels are called collaterals. When there is difficulty in blood flow through the main vessels, caused by their blockage, damage or ligation during operations, blood rushes through anastomoses into the nearest lateral vessels, which expand and become tortuous, their vascular wall is rebuilt due to changes in the muscular layer and elastic frame and they are gradually transformed into collaterals different structure than normal. Thus, collaterals exist under normal conditions, and can develop again in the presence of anastomoses. Consequently, in case of a disorder of normal blood circulation caused by an obstacle to the blood flow in a given vessel, the existing bypass blood paths - collaterals - are first turned on, and then new ones develop. As a result, impaired blood circulation is restored. The nervous system plays an important role in this process.
Thus, a collateral is a lateral vessel that carries out a roundabout flow of blood. There are two types of collaterals. Some exist normally and have the structure of a normal vessel, like an anastomosis. Others develop again from anastomoses and acquire a special structure. To understand collateral circulation, it is necessary to know those anastomoses that connect the systems of various vessels, through which collateral blood flow is established in the case of early vessels, ligation during operations and blockages (thrombosis and embolism).
Anastomoses between the branches of large arterial highways supplying the main parts of the body (aorta, carotid arteries, subclavian arteries, iliac arteries, etc.) and representing separate vascular systems are called intersystemic. Anastomoses between the branches of one large arterial line, limited to the limits of its branching, are called intrasystemic. There are anastomoses between the thinnest intraorgan arteries and veins - arteriovenous anastomoses. Through them, blood flows bypassing the microcirculatory bed when it is overfilled and, thus, forms a collateral path that directly connects the arteries and veins, bypassing the capillaries. In addition, thin arteries and veins take part in the collateral circulation, accompanying the main vessels in the neurovascular bundles and constituting the so-called perivascular and perivascular arterial and venous beds.
The importance of collateral circulation in ensuring compensatory processes in the vascular system of the brain is extremely high. Suffice it to say that the consequences of blockage of the cerebral arteries depend primarily on the possibilities of collateral blood supply, which in turn are determined by many factors.
The rich network of anastomoses between the arteries supplying blood to the brain opens up wide opportunities for the redistribution of blood between different areas of its vascular system. The need for this arises in both normal and pathological conditions. Normally, the anastomoses of the cerebral vascular system do not function continuously. They are used mainly to ensure the flow of blood into the brain pool, the blood supply of which has become insufficient due to some temporary restrictions on blood flow in the afferent vessel. Thus, it is known that when turning, tilting the head or straightening the neck, predominantly one of the carotid or vertebral arteries is compressed. This leads to a sharp decrease in pressure in it, and after this - to the flow of blood through the arteries of the circle of Willis towards the suddenly decreased intra-arterial pressure. Thus, the most important basal anastomosis - the circle of Willis - acts as a blood redistributor. For this purpose, prepared pathways of collateral blood supply are used.
Under pathological conditions, for example, when there is blockage of cerebral vessels, the role of true anastomoses increases immeasurably. The advantage of anastomoses such as the circle of Willis is that when they are included, a large amount of time is not required for the formation of collateral blood supply pathways. Of course, the timely inclusion of blood flow is the most important prerequisite for the implementation of effective collateral circulation in the brain, since the time here is limited to a very short period due to the high sensitivity of nerve cells to hypoxia. The delayed development of the collateral network in this organ is usually devoid of clinical significance, since the completion of its formation is preceded by the death of the brain substance. In this regard, it should be emphasized that the presence in patients of a developed network of collaterals, determined angiographically, is not yet a criterion for a complete blood supply to the brain. The moment when it was formed and the volume of circulatory blood supply are important.
The paths and state of collateral circulation are considered in detail by Lairbecke, Gia221 (1968).
In accordance with the structural features of the vascular system of the brain, 4 anatomical levels of collateral circulation are distinguished: one extra-human
turnip and three intracranial (Fig. 9).
Rice. 9. Scheme of anastomoses in the systems of the carotid and vertebral - the main arteries (according to Karelubi, VasardP, 1965). Arteries: 1 - subclavian, 2 - common carotid, 3 - vertebral, 4 - thyroid-cervical trunk, 5 - costocervical trunk, 6 - spinal, 7 - main, 8 - cerebellar, 9 - posterior cerebral, 10 - posterior communicating, 11 - middle cerebral, 12 - anterior cerebral, 13 - anterior communicating, 14 - external carotid artery, 15 - internal carotid artery, 16 - brachiocephalic trunk. Anastomoses between arteries: I - vertebral and external carotid, II - vertebral and spinal, III - vertebral and thyrocostal-cervical, IV - superior and inferior cerebellar arteries, V - anterior and posterior arteries of the choroid plexus, VI-VII - anterior, middle and posterior cerebral arteries, VIII - external carotid and orbital arteries. |
The extracranial level of the cerebral collateral circulation is a group of anastomoses between the carotid and subclavian-vertebral artery systems. The most important of them are: anastomosis between the occipital artery (branch of the external carotid artery) and the muscular branches of the vertebral artery, between the occipital artery and the arteries of the cervical-thyroid and costocervical trunks (branches of the subclavian artery), between the superior thyroid arteries (branches of the external carotid artery) and the inferior thyroid arteries (“branches of the subclavian artery”). The last anastomosis also connects the systems of the carotid and subclavian arteries of both sides. Both external carotid arteries are also connected to each other by the lingual and external maxillary arteries. With the help of these anastomoses, collateral circulation is carried out when the common carotid and vertebral arteries are blocked.
The intracranial levels of cerebral collateral circulation are represented by three groups of anastomoses: the circle of Willis, anastomoses between the cerebral arteries on the surface of the brain, and the intracerebral vascular-capillary network.
The role of the circle of Willis as an anastomosis has been repeatedly emphasized. It remains to complement the characteristics of its individual links. The anterior communicating artery plays a major and decisive role in providing blood supply to the cerebral hemisphere on the side of the blockage of the internal carotid artery or the proximal anterior cerebral artery. Blood flows through the posterior communicating arteries when the internal carotid artery (especially both of these arteries) is closed, and also in the opposite direction when the vertebral or proximal parts of the posterior cerebral arteries are closed. In general, this level is characterized by the automatic inclusion of connecting arteries when one of the main arteries of the head is switched off from the system, thereby maintaining a balanced blood supply to the cerebral hemispheres.
Anastomoses on the surface of the brain between the anterior, middle and posterior cerebral arteries provide favorable conditions for blood flow in the event of blockage and, consequently, a drop in pressure in the pool of one of them, i.e. in a relatively limited area of the vascular system. If there is insufficient blood flow through the anastomoses, foci of necrosis develop in areas most distant from the source of collateral blood supply. On the contrary, with circulatory failure in the brain as a whole, blood flow in the area of anastomoses, as in the branches most distant from the sources of blood supply, sharply decreases. The same is observed in relation to the long intracerebral arteries that plunge into the substance of the brain. In these cases, areas of the brain supplied by the distal, peripheral branches of the vascular system are affected: areas of adjacent blood supply to the cortex, as well as the white matter of the brain.
In addition to those described above, there are a number of other anastomoses. Of these, the greatest importance in closing the internal carotid artery is given to direct intra-extra-ranial anastomosis of one of its branches - the orbital artery with the branches of the external carotid artery in the area of the angle of the eye, forehead and dorsum of the nose. Anastomoses of the branches of the orbital and middle cerebral arteries with the arteries of the dura mater. Anastomoses of the cerebellum were discussed above. They play a significant role as collaterals when the main artery is blocked. On the surface of the brain stem and spinal cord, anastomoses are poorly represented. Therefore, the possibilities of blood redistribution here are limited. In this case, anastomoses of intracerebral arteries The role of anastomoses of the cerebral vascular-capillary network as routes of collateral blood supply to other areas of the brain when its arteries are blocked is insignificant.
The stages in the development of collateral circulation in the cerebrum were revealed (I. V. Gannushkina, 1973). It has been established that in the area of a closed artery, the acute stage of diffuse vasodilation is replaced by a chronic stage of isolation of individual collateral pathways and, to a certain extent, normalization of the state of the vessels in the rest of the area of the closed artery. In this case, collateral blood circulation of unequal volume may be established, from excessive perfusion to reduced blood flow. In accordance with this, a pronounced functional and structural restructuring of the arterial walls occurs. Previously, these vascular changes were usually taken for arteritis of unknown etiology (cerebral form of Winivarter-Buerger disease), whereas in reality they may be a secondary reaction of the arteries to changed circulatory conditions. It was also revealed that under conditions of reduced blood circulation, microemboli are formed from blood elements. The possibility of reverse development of vascular changes resulting from the transformation or slowdown of blood flow (thrombosis, recalibration of arteries) and restoration of their lumen has been shown.
The possibilities of developing adequate collateral circulation are determined by a number of factors. The main ones are: the condition of the collateral blood supply and general circulation. An important circumstance is that when the blood vessels in the brain are blocked, the process of turning on complex mechanisms to compensate for impaired blood circulation requires a certain time. Therefore, the implementation of the available possibilities of collateral circulation depends to a certain extent on the rate of development of occlusion. In cases with a high rate of closure of the vessel lumen (embolism), the development of focal changes in the brain is always observed, regardless of the level of blockage. Naturally, the scale of its consequences may vary, since they depend on many other factors.
If the rate of vessel closure is relatively slow, then, other things being equal, the localization and size of changes in the brain substance are determined by the level of arterial damage, in particular the ratio of occlusion to the circle of Willis. The most unfavorable in terms of the possibility of developing collateral circulation is blockage of the arteries within or distal to the circle of Willis, for example, thrombosis of the intracranial part of the internal carotid artery with the spread of the thrombus into the circle of Willis, since this excludes the possibility of blood entering the vessels of the hemisphere on the side of the occlusion from the vessels opposite hemisphere. Blockage of the intracranial section of the vertebral artery within the boulevard arterial circle leads to serious consequences. The clinical picture develops rapidly in these cases and is characterized by persistent focal neurological symptoms. Patients with blockage of the intracranial carotid artery in most cases die from edema and swelling of the brain due to extensive foci of necrosis of the brain matter. Bilateral blockage of the intracranial sections of the vertebral arteries is almost always fatal for patients, even in cases where their closure occurred sequentially over a long period of time. In contrast, blockage of the carotid artery outside the skull (proximal to the circle of Willis) is often asymptomatic, as is blockage of only one vertebral artery.
As for the blockage of the cerebral arteries, despite the wide network of anastomoses, the blood flow in them was considered insufficient for full-fledged collateral circulation. However, more and more often there are descriptions of a number of observations, confirmed angiographically, in which blockage of the middle cerebral artery was accompanied by minimal neurological symptoms. Angiograms show the filling of its pool with contrast agent from the vessels of neighboring areas.
The normal state of the mechanisms of self-regulation of cerebral circulation is extremely important for ensuring complete collateral circulation in the brain. However, in patients with vascular diseases of the brain they often function in an unstable mode. In this regard, the dependence of cerebral blood flow on the state of general circulation and other extracerebral factors increases.
Summarizing the data on the factors that promote or hinder the development of sufficient compensatory blood circulation and thereby determine the consequences of blockage of the cerebral arteries, the following can be identified. First of all, these are the previously noted structural features of individual areas of the vascular system of the brain, both typical and individual. These may include, in addition to the features of angioarchitectonics, the number, size of anastomoses and their varying distances from areas located within the territory of the switched off artery. Other factors are the patency of the pathways providing collateral blood flow, as well as the level (including initial) of systemic blood pressure. So, if blockage of an artery develops against the background of previous occlusion of the great vessels, then it is natural that compensatory blood flow is limited. The importance of the rate of arterial closure and the level of systemic blood pressure was mentioned above.
Rice. 10. Subclavian “stealing phenomenon” (diagram).
1 
- right subclavian artery,
2 - right vertebral artery,
3 - main artery, 4 - left vertebral artery, 5 - left subclavian artery.
Blockage of the proximal left subclavian artery. The arrows show the path of blood flow from the right vertebral artery through the basilar artery to the left vertebral artery and then to the left subclavian artery.
Under certain conditions, collateral circulation occurs in physiologically unjustified forms. This unique mechanism of circulatory disorders in the brain occurs when the proximal branches of the aortic arch (subclavian, innominate and common carotid arteries) are blocked and is called the “steal phenomenon”. It was first described in case of blockage of the initial segment of the subclavian artery and was called “subclavian syndrome about the vertebral artery” (Fig. 10). In this case, the vertebral artery on the side of the blockage functions in relation to the arm as a collateral through which, to the detriment of the brain, there is a retrograde flow of blood from the vertebrobasilar system to the arterial system of the arm. With increased work with the arm, the blood flow to the brain decreases (stealing), resulting in brainstem symptoms.
Table of contents of the topic "Topographic anatomy. Operative surgery. Stages of a surgical operation.":1. Topographic anatomy. Clinical anatomy. Surgical anatomy. Regional (regional) anatomy.
2. Body area. Part of the body. Holotopia. Skeletotopia. External landmarks in anatomy. External landmarks of the body.
3. Boundaries of the body area. Projection. Syntopy. Internal landmarks of the body. Cross sections in topographic anatomy.
4. Fascia and tissue spaces of the body. Fascia.
5. Superficial fascia of the body. Own fascia. Fascial bed. fascial sheath. Fascial sheath.
7. Operative surgery. What is operative surgery? Surgery. What is surgery? Names of operations.
8. Stages of surgery. Online access. What is online access?
9. Operative procedure. Completing the operation. Classification of surgical operations.
Clinical and topographic anatomy They are also studying such an important issue as. Collateral (roundabout) circulation exists under physiological conditions when there are temporary difficulties in blood flow through the main artery (for example, when blood vessels are compressed in areas of movement, most often in the joint area). Under physiological conditions, collateral circulation occurs through existing vessels running parallel to the main ones. These vessels are called collaterals(for example, a. collateralis ulnaris superior, etc.), hence the name of the blood flow - “ collateral circulation».
Collateral blood flow can also occur under pathological conditions - with blockage (occlusion), partial narrowing (stenosis), damage and ligation of blood vessels. When blood flow through the main vessels becomes difficult or stops, blood rushes through anastomoses into the nearest lateral branches, which expand, become tortuous, and gradually connect (anastomose) with existing collaterals.
Thus, collaterals exist under normal conditions and can develop again in the presence of anastomoses. Consequently, in case of a disorder of normal blood circulation caused by an obstacle to the blood flow in a given vessel, the existing bypass blood paths, collaterals, are first turned on, and then new ones develop. As a result, blood bypasses the area with impaired vessel patency and blood circulation distal to this area is restored.
For understanding collateral circulation it is necessary to know those anastomoses that connect the systems of various vessels through which the collateral blood flow in case of injury and ligation or in the development of a pathological process leading to blockage of a vessel (thrombosis and embolism).
Anastomoses between the branches of large arterial highways that supply the main parts of the body (aorta, carotid arteries, subclavian, iliac arteries, etc.) and representing, as it were, separate vascular systems, are called intersystem. Anastomoses between the branches of one large arterial highway, limited by the limits of its branching, are called intrasystemic.
No less important anastomoses between systems of large veins, such as the inferior and superior vena cava, portal vein. Much attention is paid to the study of anastomoses connecting these veins (cavo-caval, portocaval anastomoses) in clinical and topographic anatomy.
Collateral blood circulation (s. collateralis: synonym K. roundabout) K. along vascular collaterals, bypassing the main artery or vein.
Large medical dictionary. 2000 .
See what “collateral circulation” is in other dictionaries:
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