Development of large arteries. Open Library - open library of educational information From which arterial arches do blood vessels develop?
DEVELOPMENT OF THE HEART AND BLOOD VESSELS(Fig. 200)
The heart develops from two symmetrical rudiments, which then merge into one tube located in the neck. Due to the rapid growth of the tube in length, it forms an S-shaped loop. The first contractions of the heart begin at a very early stage of development, when muscle tissue is barely visible. In the S-shaped cardiac loop, there is an anterior arterial or ventricular part, which continues into the truncus arteriosus, divided into two primary aortas, and a posterior venous or atrial part, into which the vitelline-mesenteric veins flow, vv. omphalomesentericae. At this stage, the heart is single-cavity; its division into right and left halves begins with the formation of the atrium septum. By growing from top to bottom, the septum divides the primary atrium into two - left and right, and in such a way that subsequently the confluence of the vena cava is in the right, and the pulmonary veins are in the left. The atrial septum has a hole in the middle, foramen ovale, through which in the fetus part of the blood from the right atrium flows directly into the left. The ventricle is also divided into two halves by a septum, which grows from below towards the atrial septum, without, however, completing the complete separation of the ventricular cavities. Outside, corresponding to the boundaries of the ventricular septum, grooves appear, sulci interventriculars. Completion of the formation of the septum occurs after the truncus arteriosus, in turn, is divided by the frontal septum into two trunks: the aorta and the pulmonary trunk. The septum dividing the truncus arteriosus into two trunks, continuing into the ventricular cavity towards the ventricular septum described above and forming the pars membranacea septi interventricular, completes the separation of the ventricular cavities from each other (see Fig. 200).
The right atrium is initially adjacent to the sinus venosus, which is made up of three pairs of veins: the duct of Cuvier (brings blood from the entire body of the embryo), the vitelline vein (brings blood from the yolk sac) and the umbilical vein (from the placenta). During the 5th week, the opening leading from the sinus venosus into the atrium greatly expands, so that eventually the wall becomes the wall of the atrium itself. The left process of the sinus, together with the left duct of Cuvier flowing here, is preserved and remains as sinus coronarius cordis. When entering the right atrium, the sinus venosus has two venous valves, valvulae venosae dextra et sinistra. The left valve disappears, and the valvula venae cavae inferior and valvula sinus coronarii develop from the right. As a developmental anomaly, the 3rd atrium may result, representing either a distended coronary sinus into which all the pulmonary veins flow, or a separated part of the right atrium.
Development of arteries. Reflecting the transition in the process of phylogenesis from the gill circulation to the pulmonary circulation, in humans, in the process of ontogenesis, the gill arteries are first formed, which are then transformed into the arteries of the pulmonary and body circulation (Fig. 201).
In a 3-week-old embryo, the truncus arteriosus, emerging from the heart, gives rise to two arterial trunks called the ventral aortas (right and left). The ventral aortas go in an ascending direction, then turn back to the dorsal side of the embryo; here they, passing on the sides of the chord, go in a descending direction and are called dorsal aortas. The dorsal aortas gradually move closer to each other and in the middle section of the embryo merge into one unpaired descending aorta. As visceral arches develop at the head end of the embryo, the so-called branchial aortic arch or artery is formed in each of them; these branchial arteries connect the ventral and dorsal aortas on each side. Thus, in the region of the visceral (branchial) arches, the ventral (ascending) and dorsal (descending) aortas are connected to each other using 6 pairs of branchial arteries.
Subsequently, part of the branchial arteries and part of the dorsal aortas, especially the right one, are reduced, and from the remaining primary vessels large pericardial and main arteries develop, namely: truncus arteriosus, as mentioned above, is divided by the frontal septum into the ventral part from which the pulmonary trunk is formed, and the dorsal aorta turns into the ascending aorta. This explains the location of the aorta behind the pulmonary trunk. Following the blood flow from the center to the periphery, it should be noted that the last pair of gill arteries, which in lungfishes and amphibians acquires a connection with the lungs, also turns into two pulmonary arteries in humans - the right and left, branches of the truncus pulmonalis. Moreover, if the right sixth branchial artery is preserved only in a small proximal segment, then the left one remains along its entire length, forming the ductus arteriosus Botalli, which connects the pulmonary trunk with the end of the aortic arch, which is important for the blood circulation of the fetus. The fourth pair of gill arteries is preserved on both sides throughout its entire length, but gives rise to various vessels. The left fourth branchial artery, together with the left ventral aorta and part of the left dorsal aorta, form the aortic arch, arcus aortae.
The proximal segment of the right ventral aorta turns into the brachiocephalic trunk, truncus brachiocephalicus, the right fourth branchial artery turns into the beginning of the right subclavian artery, a. subclavia dextra. The left subclavian artery arises from the left dorsal aorta caudal to the last branchial artery. The dorsal aortas in the area between the third and fourth branchial arteries are obliterated; in addition, the right dorsal aorta is also obliterated from the origin of the right subclavian artery to its confluence with the left dorsal aorta.
Both ventral aortas in the area between the fourth and third aortic arches are transformed into the common carotid arteries, aa. carotides communes, and due to the above transformations of the proximal part of the ventral aorta, the right common carotid artery appears to arise from the brachiocephalic trunk, and the left - directly from the arcus aortae. Further along the ventral aortas turn into the external carotid arteries, aa. carotides externae.
The third pair of branchial arteries and the dorsal aortas in the segment from the third to the first branchial arch develop into the internal carotid arteries, aa. carotides internae, which explains that the internal carotid arteries lie more laterally in adults than the external ones. The second pair of gill arteries turns into aa. linguales and pharyngeae, and the first pair - into the maxillary, facial and temporal arteries. When the normal course of development is disrupted, various anomalies occur.
From the dorsal aortas arise a series of small paired vessels running dorsally on both sides of the neural tube. Because these vessels extend at regular intervals into the loose mesenchymal tissue located between the somites, they are called dorsal segmental arteries. In the neck area, they are early connected on both sides of the body by a series of anastomoses, forming longitudinal vessels - the vertebral arteries.
At the level of the 6th, 7th and 8th cervical segmental arteries, the kidneys of the upper extremities are formed. One of the arteries, usually the 7th, grows into the upper limb and increases with the development of the arm, forming the distal section of the subclavian artery (its proximal section develops, as already indicated, on the right from the 4th branchial artery, on the left it grows from the left dorsal aorta, with with which the 7th segmental arteries enter into communication). Subsequently, the cervical segmental arteries are obliterated, as a result of which the vertebral arteries appear to arise from the subclavian ones.
The thoracic and lumbar segmental arteries give rise to the aa. intercostales posteriores et aa. lumbaies.
The visceral arteries of the abdominal cavity develop partly from aa. omphalomesentericae (yolk-mesenteric circulation) and partly from the aorta.
The arteries of the limbs are initially laid along the nerve trunks in the form of loops. Some of these loops (along the n. femoralis) take over and develop into the main arteries of the limbs, others (along the n. medianus, n. ischiadicus) remain companions of the nerves.
Vein development(Fig. 202).
At the beginning of the placental circulation, when the heart is in the cervical region and is not yet divided by partitions into venous and arterial halves, the venous system has a relatively simple structure. Large veins run along the body of the embryo: in the head and neck area - the anterior cardinal veins (right and left) and in the rest of the body - the right and left posterior cardinal veins. Approaching the venous sinus of the heart, the anterior and posterior cardinal veins on each side merge, forming the so-called Cuvier ducts (right and left), which, initially having a strictly transverse course, flow into the venous sinus of the heart. Along with the paired cardinal veins, there is another unpaired venous trunk - the primary vena cava inferior, which, in the form of a small vessel, also flows into the venous sinus. Thus, at this stage of development, three venous trunks flow into the heart: the paired duct of Cuvier and the unpaired primary inferior vena cava.
Further changes in the location of the venous trunks are associated with the displacement of the heart from the cervical region down and the division of its venous part into the right and left atria. Due to the fact that after the division of the heart, both ducts flow into the right atrium, the blood flow in the right duct of Cuvier is in more favorable conditions. In this regard, an anastomosis appears between the right and left anterior cardinal veins, through which blood from the head flows into the right Cuvier duct. As a result, the left Cuvier duct ceases to function, its walls collapse and it becomes obliterated, with the exception of a small part that becomes the coronary sinus of the heart, sinus coronarius cordis. The anastomosis between the anterior cardinal veins gradually intensifies, turning into vena brachiocephalica sinistra, and the left anterior cardinal vein itself below the origin of the anastomosis is obliterated. The right anterior cardinal vein goes to the formation of two vessels: the part of it, located above the confluence of the anastomosis, turns into vena brachiocephalica dextra, and the part below it, together with the right Cuvier duct, is transformed into the superior vena cava, thus collecting blood from the entire cranial half of the body. If the described anastomosis is underdeveloped, a developmental anomaly in the form of two superior vena cava may result.
Formation of the inferior vena cava associated with the appearance of anastomoses between the posterior cardinal veins. One anastomosis, located in the iliac region, drains blood from the left lower extremity to the right posterior cardinal vein; as a result, the segment of the left posterior cardinal vein located above the anastomosis is reduced, and the anastomosis itself turns into the left common iliac vein. The right posterior cardinal vein in the area before the confluence of the anastomosis (which became the left common iliac vein) is transformed into the right common iliac vein, and from the confluence of both iliac veins to the confluence of the renal veins it develops into the secondary inferior vena cava. The rest of the secondary inferior vena cava is formed from the unpaired primary inferior vena cava flowing into the heart, which connects with the right inferior cardinal vein at the junction of the renal veins (here there is a 2nd anastomosis between the cardinal veins, which drains blood from the left kidney) thus, the finally formed inferior vena cava is composed of 2 parts: from the right posterior cardinal vein (before the confluence of the renal veins) and from the primary inferior vena cava (after the confluence). Since the inferior vena cava drains blood to the heart from the entire caudal half of the body, the importance of the posterior cardinal veins weakens, they lag behind in development and turn into v. azygos (right posterior cardinal vein) and in v. hemiazygos et hemiazygos accessoria (left posterior cardinal vein). V. hemiazygos flows into v. azygos through the 3rd anastomosis, developing in the thoracic region between the former posterior cardinal veins
Portal vein is formed in connection with the transformation of the vitelline-mesenteric veins, through which blood from the yolk sac comes to the liver Vv. omphalomesentericae in the space from the confluence of the mesenteric vein to the portal of the liver turns into the portal vein.
When placental circulation is formed, the emerging umbilical veins enter into direct communication with the portal vein, namely: the left umbilical vein opens into the left branch of the portal vein and thus carries blood from the placenta to the liver, and the right umbilical vein is obliterated. Some of the blood, however, goes in addition to the liver through an anastomosis between the left branch of the portal vein and the terminal segment of the right hepatic vein. This previously formed anastomosis, together with the growth of the embryo, and consequently the increase in blood passing through the umbilical vein, significantly expands and turns into the ductus venosus (Arantii). After birth, it becomes obliterated into the ligamentum venosum (Arantii).
Pericardial development
In the early stage of heart development, there are two pericardial cavities, which are formed even before the fusion of the two cardiac primordia into a single tube. The epicardial part of the pericardial sac develops from the somato-pleura, and the parietal layer - from the somato-pleura. The two leaves are connected by the dorsal mesocardium, after absorption of which the two leaves are connected to each other only where the lower and upper ends of the primary cardiac tube seem to pierce them. As the heart tube rotates, the two ends fall one after the other. When bent, the layers of the pericardium overlap each other, and they are separated from each other only by the transverse sinus of the pericardium. The anterior part of the pericardium encircles two large arteries, and the posterior part is where the large veins enter the atrium.
Development of large arteries
The cranial end of the primary cardiac tube continues into the truncus arteriosus. This trunk is divided into two branches, which pass in a small area along two sides of the body ventricularly cranially and then, bending, continue in the caudal direction. From the ventral segment of the aorta arise the branchial arch arteries (primary aortic arches), which flow posteriorly into the descending aorta, which arises from the fusion of the two aortic arches. The part reaching the primary branchial arch is the primary ascending aorta, which continues through the primary aortic arch into the primary descending aorta. It then passes along the two sides of the chorda dorsalis in a caudal direction and continues into the umbilical artery. Thus, the umbilical artery is the end of the aorta. Later, the two dorsal aortas, united with the common abdominal aorta, continue into the caudal aorta, and thus the umbilical artery, which was previously the end of the aorta, becomes a collateral branch.
The arteries of the gill arches appear towards the end of the second week, the first four immediately one after the other, followed by the sixth and later the fifth. Some of them quickly disappear: the first - by the end of the third week, the second and fifth - by the end of the fourth week. Ultimately, in this way, only the third, fourth and sixth arteries of the branchial arches are preserved. From the ventral aorta on both sides the primary external carotid artery develops, and from the dorsal aorta the primary internal carotid artery develops. Two pairs of carotid arteries are connected to each other by the artery of the third costal arch. The part of the internal carotid artery located under the artery of the third branchial arch disappears, and the common trunk becomes the initial segment of the external carotid artery. A direct continuation of this trunk is the external carotid artery, while the internal carotid artery branches to the side.
The fourth primary aortic arch behaves differently on the right side than on the left. From the left-sided fourth primary aortic arch, the aortic arch develops as a direct continuation of the left ventral aorta. This arch then continues back into the left descending aorta (later into the common descending aorta). On the right side, the ventral aorta also continues into the fourth primary aortic arch, and the dorsal aorta closes before reaching the common trunk. The innominate artery arises from the right ventral aorta, and the initial segment of the subclavian artery is formed from the dorsal aorta and the aorta of the fourth branchial arch.
The truncus arteriosus is divided by a septum into the anterior pulmonary artery and the posterior aorta. The artery of the sixth branchial arch joins the pulmonary artery and serves as the basis of the pulmonary arteries (on both sides it goes to the lung primordia). On the right side, its distal end disappears, and the right branch of the pulmonary artery develops from the proximal part. On the left side, the left branch of the pulmonary artery is formed from the initial segment, and the ductus Botallus is formed from the distal part.
Thus, at the beginning of development there are two descending arteries, but these two vessels very early, in the third week, gradually merge into a common descending aorta. By the end of the fourth week, there is only one descending aorta, from which symmetrical branches arise. From the sixth branch, directly from the aorta, the left subclavian artery develops, while on the right side, in the manner already mentioned, with the help of the artery of the fourth branchial arch, the right subclavian artery is indirectly formed. As the heart moves caudally, the ascending aortas are slightly retarded - the right one is larger than the left - and thus the left subclavian artery becomes closer to the carotid artery.
The umbilical artery descends lower and lower in such a way that one caudal arterial branch always grows into it while the original superior branch resolves. Thus, the descending aorta becomes longer and longer. The femoral artery later develops from the umbilical artery, while the initial segment of the umbilical artery forms the iliac artery.
We touch upon the development of the remaining vessels only briefly. The arteries of the skull arise from the two carotid arteries and are connected with the vertebral artery, which arose from the longitudinal anastomoses of the cervical segments. From the descending aorta grow ventral branches to the intestinal tract and the organs developing from it. Paired dorsal branches are directed according to the initial segmentation of the body to the central nervous, skeletal and muscular systems. Paired lateral branches turn into arteries going to the kidneys, adrenal glands and genitals.
Development of blood vessels
Human blood vessels develop from mesenchyme ahead of the development and differentiation of organs and tissues. The origin of microvessels is associated with mesenchymal cells and the yolk sac, where the first foci of hematopoiesis, and around them arise from primary endothelial cells first organ microvessels. Along the yolk stalk they grow into the primary intestine and form the first intraorgan capillary networks in it, with which extraorgan and main vessels are subsequently connected.
At the 3rd week, the right and left hearts grow from the truncus arteriosus of the heart. ventral and the same two dorsal aortas. The ventral aortas are located in front of the primary gut, and the dorsal ones behind it, along the chord and below merge into the common trunk of the abdominal aorta. Both pairs of aortas at the head end of the embryo in the region of the visceral arches of the primary intestine are connected to each other by 6 pairs of aortic arches.
With the development of the head, neck, trunk and limbs, and with them the brain, heart and all internal organs, restructuring of the embryonic vascular system occurs at different times. It starts with reduction of part of the aortic arches (I, II,V) and formations from the third, fourth and sixth arches of the arteries of the head, neck and chest cavity. The anterior section of the ventral aorta from the I to III aortic arch turns into the external carotid artery, and the internal carotid artery arises from the anterior section of the dorsal aorta and the third arch. The section of the left ventral aorta at the level of the III-IV arches turns into the longer left common carotid artery. The terminal part of the right ventral aorta and part of the IV arch form the right subclavian artery and the right common carotid artery. The fourth arch becomes the aortic arch proper, which connects the ascending aorta with the left dorsal aorta, which gradually becomes the descending aorta. At the junction, due to the difference in diameter, a narrowness occurs, called the aortic isthmus. The sixth aortic arch turns into the pulmonary arteries, the left of which fuses with the own aortic arch through the narrow arterial (Botallov) duct, which is a necessary device for the intrauterine circulation of the fetus.
The lateral branches of the ventral and dorsal aortas are called intersegmental and segmental (lateral and medial), since they are directed to and between segmentally located somites. From the branches of the dorsal aortas the long left subclavian, vertebral and basilar arteries, posterior intercostal, and lumbar arteries develop. The subclavian arteries, growing into the upper limbs, create axial arteries, from which the common interosseous arteries of the forearms remain in the process of development. The segmentation of the lateral and ventral arteries of the dorsal aortas is disrupted over time. The lateral segmental arteries give rise to paired abdominal arteries: phrenic, renal, ovarian. The ventral arteries form unpaired vessels: the celiac trunk, mesenteric arteries. From the caudal arteries arise the umbilical ones, and from them the axial arteries of the lower extremities.
Veins are formed in the 4th week by two paired cardinal trunks, anterior and posterior, vitelline and umbilical venous vessels. The cardinal trunks lie ventral to the dorsal aortas. In front they are called precardinal veins, in back they are called postcardinal veins, but both pairs flow into common cardinal veins connected to the venous sinus of the heart. The development of the vena cava is associated with the restructuring of the pre- and postcardinal veins and anastomoses between them, the reduction of the venous sinus and the formation of a four-chambered heart. The formation of the inferior vena cava is strongly influenced by the primary kidney (mesonephros) and the restructuring of the right posterior cardinal vein. The superior vena cava arises from the right common cardinal and right precardinal veins. The portal vein is formed under the influence of the vitelline veins and the development of the liver with its vascular devices for intrauterine circulation: the ductus venosus, umbilical veins and anastomoses.
Anomalies development of blood vessels are more common in aortic arches, especially those that undergo reduction. If the IVth right and left arches and the beginning of the dorsal aortas are preserved, an aortic ring can form around the thoracic part of the trachea and esophagus. It is possible that the pulmonary veins flow not into the left atrium, but into the superior vena cava, azygos or brachiocephalic veins. Particularly severe defects occur when the development of the heart and the main vessels associated with it is impaired, when the aorta and pulmonary trunk, vena cava and pulmonary veins change positions in different variants and combinations. According to anatomical and functional characteristics, the variety of variant structures of arteries and veins can be divided into structural anomalies without hemodynamic disturbances and developmental defects accompanied by blood flow disorders (pathological redistribution of venous outflow between the atria or arterial blood flow between the ventricles and atria).
STAGES OF ARTERY DEVELOPMENT- the process of arterial development consists of two stages: 1) the stage of formation of the primary capillary network evenly distributed throughout the body of the embryo. 2) stage of trunking and reduction. This stage begins with the stage of a simple tubular heart and actively occurs at the stage of the sigmoid heart.
VENTRAL AORTA – a paired vessel in the region of the head end of the embryo, formed as a result of division of the arterial trunk of the heart. At the level of the future pharynx, the ventral aortas unfold caudally and are called dorsal aortas.
DORSAL AORTA – continuation of the ventral aortas in the caudal direction. In the fourth week of development, the aortas fuse to form the azygos dorsal aorta.
AORTIC ARCH – six pairs of arterial trunks passing through the branchial arches and connecting the ventral and dorsal aortas. The first pair of arches represents the place of transition of the ventral aortas to the dorsal ones. Aortic arches are the material for the vessels of the head, neck, shoulder girdle and upper limb.
Transformation of the aortic arches - the first, second and fifth aortic arches are almost completely reduced; sections of the ventral aortas above the third arches on both sides are trunked in the form of external carotid arteries; the third aortic arches and dorsal aortas cranial to this level are trunked into the internal carotid arteries; sections of the ventral aortas between the third and fourth arches become common carotid arteries, and similar sections of the dorsal aortas are reduced; the fourth right aortic arch is preserved as the proximal part of the right subclavian artery. The same arch on the left becomes the aortic arch. The portion of the right ventral aorta caudal to the fourth arch becomes the brachiocephalic trunk, and a similar portion of the left ventral aorta becomes the ascending aorta; the left dorsal aorta is below the level of the fourth arch and the entire azygos dorsal aorta becomes the descending aorta. The right dorsal aorta from the fourth arch to the azygos dorsal aorta is reduced. The sixth aortic arch is the last to change at the moment when the arterial trunk of the sigmoid heart divides into the pulmonary trunk and the aorta. In this case, the arch retains connection only with the pulmonary trunk and connects it with the dorsal aorta. From the middle of every sixth arch, vessels form into the anlage of the lungs. The central half of the right sixth arch and the highway to the anlage of the right lung become the right pulmonary artery, and similar areas on the left turn into the left pulmonary artery. The peripheral part of the sixth aortic arch on the right is reduced, and on the left it remains in the form of the Botalov duct.
SEGMENTAL ARTERIES – segmental vessels, represented by dorsal, lateral and ventral segmental arteries.
TRANSFORMATION OF DORSAL SEGMENTAL ARTERIES - several groups of dorsal vessels are distinguished. The first, seven arteries, arises from the paired dorsal aortas from level 4-5 of the aortic arch and above. The most caudal arteries are trunked, forming the subclavian artery on the left, and the distal part of the subclavian artery on the right. The lateral ends of this group of dorsal arteries form longitudinal anastomoses in the form of vertebral arteries. The second group of dorsal segmental arteries arises from the azygos dorsal aorta. The lateral ends of these vessels are transformed into longitudinal anastomoses in the form of internal thoracic arteries, and the dorsal arteries themselves are preserved in the form of posterior and anterior intercostal arteries. Another group of dorsal segmental arteries become the lumbar arteries, and their longitudinal anastomoses become the inferior epigastric arteries.
TRANSFORMATION OF LATERAL SEGMENTAL ARTERIES - these arteries initially represent the vessels of the mesonephros and gonadal anlage. Since mesonephros is reduced to metanephros, the vessels reappear, and the vessels of the gonads are preserved and lengthened as the organs descend.
TRANSFORMATION OF VENTRAL SEGMENTAL ARTERIES - initially these vessels connect the embryo with the yolk sac. As the vitelline mesenteric circle is reduced, the vessels come closer together, lose their pairing and form three highways to the organs of the gastrointestinal tract - the celiac trunk, the superior and inferior mesenteric arteries.
Anomalies of ARTERY DEVELOPMENT - absence or underdevelopment of arteries (the result of excessive reduction); additional arteries (incomplete reduction); right-sided aorta; duplication of the aorta; anomalies of the large vessels of the heart; anomalies in the position and course of arteries.
CLASSIFICATION OF ARTERIES
Development of blood vessels (human anatomy)
Blood islands appear in the wall of the yolk sac and chorion at the end of the 2nd and beginning of the 3rd week of development. Along the periphery of the blood islands, mesenchymal cells separate from the central ones and turn into endothelial cells of extraembryonic blood vessels. Intraembryonic vessels (bodies) are also formed from blood islands and in the 3rd week of development they come into contact with extraembryonic blood vessels (vessels of the yolk sac and chorion).
Arterial development .
In a 3-week-old embryo, the truncus arteriosus originates from the heart primordium, which divides into the right and left dorsal aorta. The dorsal aortas in the middle part of the body merge into one trunk of the abdominal aorta. At the cephalic end of the body at this time (3-4 weeks) 6 gill arches are formed, in the mesenchyme of which 6 aortic arches lie. These aortic arches connect the ventral and dorsal aortas (Fig. 148). This structure of the arteries of the embryo resembles the vascular system of animals with gill apparatus.
Although all branchial arteries cannot be simultaneously detected in the human embryo, since their development and restructuring occur at different times, the 1st and 2nd aortic arches atrophy before the 5th and 6th arches appear. The 5th arch exists for a short time and turns into a vestigial organ. The 3rd, 4th and 6th aortic arches, as well as the roots of the dorsal and ventral aortas, reach full development (Fig. 149).
Rice. 149. Restructuring of arterial arches in embryos (according to Patten). a - diagram of the location of all aortic arches; b - early stage of restructuring of the aortic arches; c - final picture of the restructuring. a: 1 - aortic root; 2 - dorsal aorta; 3 - aortic arch; 4 - external carotid artery; 5 - internal carotid artery; b: 1 - common carotid artery; 2 - branch from the sixth arch to the lung; 3 - left subclavian artery; 4 - thoracic segmental arteries; 5 - right subclavian artery; 6 - cervical segmental arteries; 7 - external carotid artery; 8 - internal carotid artery; c: 1 - anterior cerebral artery; 2 - middle cerebral artery; 3 - posterior cerebral artery; 4 - main artery; 5 - internal carotid artery; 6 - posterior inferior cerebellar artery; 7, 11 - vertebral artery; 8 - external carotid artery; 9 - common carotid artery; 10 - ductus arteriosus; 12 - subclavian artery; 13 - internal mammary artery; 14 - thoracic aorta; 15 - pulmonary trunk; 16 - shoulder-head trunk; 17 - superior thyroid artery; 18 - lingual artery;
19 - maxillary artery; 20 - anterior inferior cerebellar artery; 21 - artery of the bridge; 22 - superior cerebellar artery; 23 - ophthalmic artery; 24 - pituitary gland; 25 - arterial circle
Simultaneously with these transformations, a frontal septum appears in the initial part of the common trunk of the ventral aortas, dividing it into anterior and posterior parts. The pulmonary trunk is formed from the anterior part, and the ascending part of the future aorta is formed from the posterior part. This part of the aorta connects with the 4th left aortic arch and they form the aortic arch. The terminal part of the right ventral aorta and the 4th right aortic arch give rise to the right subclavian artery. The right and left ventral aortas, located between the 4th and 3rd aortic arches, are transformed into the common carotid arteries.
The development of the initial part of the right subclavian artery is discussed above. The left subclavian artery originates from the aortic arch itself caudal to the ductus arteriosus, which connects the aortic arch and the pulmonary trunk. After the heart descends, the subclavian artery grows into the kidney of the upper limb.
The kidneys of the hind limbs appear only after the development of the placental circulation. The paired artery of the leg bud originates from the umbilical artery in the place where it passes closest to the base of the limb bud. In the kidney of the limb, the vessel occupies an axial position, located near the sciatic and femoral nerves. The iliac artery develops better and becomes the main arterial pathway supplying the lower extremities.
Vein development .
The development of veins begins with rudiments that have bilateral symmetry (Fig. 150). The paired anterior and posterior cardinal veins on the right and left sides of the embryo's body unite into common cardinal veins, which drain into the venous sinus of the simple tubular heart. In an adult, paired veins are preserved only in the peripheral parts of the body. Large veins develop as unpaired formations located on the right side of the body. They flow into the right half of the heart.
Rice. 150. Development of veins in a 4-week embryo (according to Patten). 1 - anterior cardinal vein; 2 - common cardinal vein; 3 - umbilical vein; 4 - vitelline-mesenteric vein; 5 - subcardinal vein; 6 - posterior cardinal vein; 7 - developing subcardinal plexus in the mesonephros; 8 - liver
Further changes in the venous system are associated with the formation of a four-chambered heart and its displacement to the caudal end of the body. After the formation of the right atrium, both common cardinal veins flow into it.
The appearance of the posterior cardinal veins is mainly associated with the development of the middle kidney. With the reduction of the middle kidney, the posterior cardinal veins disappear. They are replaced by subcardinal veins located along the body of the embryo parallel to the posterior cardinal veins. The subcardinal veins at the level of the terminal kidney are connected by a venous anastomosis called the subcardinal sinus. Blood from the lower part of the body at this time no longer flows through the posterior cardinal veins, but flows into the heart through the subcardinal sinus. Above it, the cranial parts of the subcardinal veins turn into paired and semi-unpaired veins, and the caudal parts into iliac veins, through which blood flows from the pelvis and lower extremities.
The formation of the portal vein is influenced by the outflow of venous blood from the primary intestine through the vitelline veins of the yolk sac. The vitelline veins drain into the venous sinus of the heart from behind. On the way to the liver, the vitelline mesenteric veins meet the liver primordium, where they split into several branches, which subsequently establish a connection with the inferior vena cava. With the disappearance of the yolk sac and the growth of the intestine, the vitelline veins atrophy, and their mesenteric part is transformed into the portal vein. This development is facilitated by the flow of venous blood from the intestines, stomach, spleen and pancreas.
Anomalies in the development of blood vessels .
The most common developmental anomalies occur in derivatives of the aortic arches, although small arteries of the trunk and extremities can have a diverse structure and different topography options. If the right and left 4-branchial aortic arches and the roots of the dorsal aortas are preserved, a formation in the form of an aortic ring may occur. This ring encloses the esophagus and trachea. There is a developmental anomaly in which the right subclavian artery arises from the aortic arch more caudally than all other branches of the aorta.
venous or azygos veins. Structural anomalies are also found in the superior vena cava.
The anterior cardinal veins sometimes develop into independent venous trunks - the superior vena cava. The wide communication of the posterior cardinal and subcardinal veins at the level of the kidneys with the help of the subcardinal sinus creates the possibility of various anomalies in the topography of the inferior vena cava and its anastomoses.
Arteries of the pulmonary circulation (human anatomy) The arteries of the pulmonary circulation include pulmonary trunk
, truncus pulmonalis. It starts from the conus arteriosus of the right ventricle, located on the anterior surface of the base of the heart, covering the beginning of the aortic arch in front and to the left. ¾ of the length of the pulmonary trunk lies intrapericardially, and ¼ is not covered by the pericardial membrane. At the point where it leaves the heart, the pulmonary trunk has a semilunar valve, which prevents blood from returning to the right ventricle during diastole. In the initial part, the pulmonary trunk has a diameter of 2.5 cm.
Under the aortic arch (at the level of the IV thoracic vertebra), the pulmonary trunk is divided into the right and left pulmonary arteries, aa. pulmonales dextra et sinistra. Between the lower wall of the aortic arch and the division of the pulmonary trunk there is an arterial ligament, lig. arteriosum. This ligament is a reduced ductus arteriosus that exists in the prenatal period.
The right pulmonary artery lies in a horizontal plane behind the ascending aorta. At the right edge of the aorta, the right pulmonary artery is covered by the superior vena cava, and behind it is the right bronchus. At the hilum of the lung, the right pulmonary artery is covered with pleura, is located in front and below the right bronchus and breaks up into lobar and then segmental branches of the corresponding segments of the lung.
