Rental block
Development of arteries in ontogenesis
At the 3rd week of embryonic development, two ventral aortas arise from the truncus arteriosus of the heart. With the help of 6 pairs of aortic arches (branchial arteries), they connect to initial departments right and left dorsal aortas (Figure 1). Three groups of arteries arise from the dorsal aortas: intersegmental dorsal arteries, lateral segmental arteries, and ventral segmental arteries.
Fig.1. Differentiation of branchial arteries
As the heart and system develop blood vessels brain development occurs spinal cord, internal organs and limbs. All this affects the restructuring of the bloodstream and arteries, in particular, the I, II and V aortic arches are soon reduced. Therefore, the main importance in the formation of the arteries of the head, neck and chest cavity have III, IV and VI aortic arches, as well as sections of the right and left ventral and dorsal aortas.
The frontal part of each ventral aorta from the I to III aortic arch turns into the external carotid artery, and each III aortic arch and the anterior portion of the dorsal aorta associated with the brain turns into the internal carotid artery. The section of the dorsal aorta between the III and IV aortic arches is reduced, and the corresponding section of the ventral aorta turns into the common carotid artery.
In contrast to the III pair of aortic arches, from which arteries of the same name are formed on the right and left, the transformations undergone by the right and left IV aortic arches are different: the left IV arch, the diameter of which increases significantly, becomes the arch of the definitive aorta, which connects the ascending part of the aorta with the left dorsal aorta. In this regard, the latter turns into the descending part of the aorta, and the right dorsal aorta (posterior to the IV right aortic arch) is reduced, the IV right aortic arch becomes the proximal portion of the subclavian artery, and that portion of the right ventral aorta (between the right III and IV aortic arches) , from which it departs, turns into a short brachiocephalic trunk; its branches are thus the right common carotid and right subclavian arteries. Left subclavian artery develops not from the aortic arches, but due to one of the intersegmental dorsal arteries - a branch of the left dorsal aorta. As a result, the brachiocephalic trunk, left common carotid and left subclavian arteries depart from the definitive aortic arch.
The sixth pair of aortic arches, after dividing the arterial trunk into the ascending aorta and the pulmonary trunk, retains its connection with the pulmonary trunk, i.e., it becomes its branches. Both VI arches give off thin branches (future pulmonary arteries) to the lungs, after which the right VI arch loses connection with the dorsal aorta, and its distal section is completely reduced. The left VI aortic arch retains its connection with the left dorsal aorta in the form of a wide arterial (botallian) duct, through which in the fetus blood from the pulmonary trunk follows to the aorta; After birth, the duct is empty, and instead of it there is an arterial ligament.
Changes undergone by the intersegmental dorsal arteries: they are divided into dorsal and ventral branches. At the level of the neck and head, the dorsal branches form the vertebral artery, and closer to the anterior (cranial) the basilar artery and its branches; in the torso area they form the posterior intercostal and lumbar arteries, which supply blood to the walls of the body. Their ventral branches form the left subclavian artery and the distal portion of the right subclavian artery. During the development of the upper limbs, the subclavian artery grows into the latter and each of them is called the axial artery of the upper limb, the remnants of which in an adult are the common interosseous artery on the forearm.
The segmentation of the anlage of the lateral and ventral segmental arteries is lost during development. The lateral segmental arteries form the paired phrenic, renal, adrenal and testicular (ovarian) arteries. From the ventral segmental arteries, vitelline arteries are formed, due to which unpaired arteries develop, supplying blood to organs abdominal cavity, celiac trunk, superior and inferior mesenteric arteries. The caudal ventral segmental arteries become the right and left umbilical arteries; the axial artery of the lower limb (a. axialis membri inferioris) departs from the beginning of each of them. Subsequently, it undergoes reverse development, and in an adult it is represented by the thin peroneal and very thin artery accompanying sciatic nerve.
In connection with the development of the pelvic organs and especially the lower extremities, the iliac arteries (common, external and internal) achieve significant development. In this case, the umbilical artery becomes a branch of the internal iliac, and the external iliac, in the form of the main arterial line, continues to the lower limb and forms the femoral, popliteal and posterior tibial arteries.
Age characteristics arteries in ontogenesis
After the birth of a child, as age increases, the diameter, circumference, thickness of the walls of the arteries and their length increase. The level of departure of the arterial branches from the main arteries and even the type of their branching also changes. The diameter of the left coronary artery prevails over the diameter of the right coronary artery in all people age groups. The most significant differences in the diameter of the right and left coronary arteries are observed in newborns and children aged 11-14 years. In elderly people over 75 years of age, there is a slight increase in the diameter of the right coronary artery (compared to the left).
Diameter of the common carotid artery in children early age equal to 3-6 mm, and in adults 9-14 mm; The diameter of the subclavian artery increases most intensively from the moment the child is born to 4 years of age. In the first 10 years of life, the middle artery has the largest diameter of all cerebral arteries. In the early childhood the intestinal arteries are almost all the same diameter and the difference between the diameter of the main artery and its branches of the 2nd and 3rd orders is small, however, as the child’s age increases, this difference increases. During the first 5 years of a child’s life, the diameter of the ulnar artery increases more rapidly than the radial artery, but later the diameter of the radial artery prevails. The circumference of the arteries also increases: for example, the diameter of the aorta in an adult is 4.5 times greater than in a newborn.
The length of the arteries increases in proportion to the growth of the body and limbs. For example, by the age of 50, the length of the descending aorta increases almost 4 times, while the length of the thoracic part increases faster than the abdominal part. The arteries supplying blood to the brain develop most intensively until 3-4 years of age, surpassing other vessels in growth rates; The anterior cerebral artery grows most rapidly in length. As age increases, the arteries that supply blood also lengthen. internal organs, and the arteries of the superior and lower limbs. Thus, in newborns and infants, the inferior mesenteric artery has a length of 5-6 cm, and in adults it is 16-17 cm.
The levels of the origin of the arterial branches from the main arteries in newborns and children, as a rule, are located more proximally, and the angles at which these vessels depart are greater in children than in adults. In some cases, the radius of curvature of the arcs formed by the vessels also changes. For example, in newborns and children of all age groups up to 12 years, the aortic arch has a larger radius of curvature than in adults.
In proportion to the growth of the body and limbs and, accordingly, the increase in the length of their arteries, a partial change in the topography of these vessels occurs. In newborns, the aortic arch is above level I thoracic vertebra, in people 17 x 20 years old at level II, at 25 x 30 years old at level III. The topography of the arteries of the extremities also partially changes. For example, in a newborn, the projection of the ulnar artery corresponds to the anteromedial edge of the ulna, and the radial artery corresponds to the anteromedial edge radius. With age, the ulnar and radial arteries move along (relative to the midline of the forearm) in the lateral direction, and in children over 10 years of age these arteries are located and projected in the same way as in adults. Projection of the femoral and popliteal arteries in the first years of a child’s life, it also shifts in the lateral direction from the midline of the thigh, with the first of them approaching the medial edge femur, and the second to the midline of the popliteal fossa. There is a change in the topography of the palmar arches. Superficial palmar arch in newborns and children younger age located proximal to the middle of the II and III metacarpal bones.
As age increases, the type of branching of the arteries also changes (Figure 3). Thus, in a newborn, the type of branching of the coronary arteries is scattered; by the age of 6–10 years, the main type is formed, which persists throughout a person’s life.
At the time of birth, the walls of the arterial bed have three membranes (outer, middle and inner). Peripheral resistance, blood pressure and blood flow velocity in healthy children of the first years of life are less than in adults. With age, the circumference, diameter, wall thickness and length of the arteries increase.
The lumen area of the ascending aorta increases from 23 mm2 in newborns to 107 mm2 in 12-year-old children, which correlates with an increase in heart size and cardiac output. The thickness of the walls of the ascending aorta increases rapidly until the age of 13.
At 40-45 years old, the aortic arch is located at the height of the IV thoracic vertebra, and in elderly and old people - at the level of the intervertebral disc, between the IV and V thoracic vertebrae.
The superficial palmar arch in adults is projected at the level of the middle of the third metacarpal bone.
Age and level blood pressure(BP) are among the most significant factors influencing arterial stiffness.
Thus, the main age-related changes include:
- The level of departure of individual branches from the main arteries and the type of their branching change. In newborns and children, the origins of the great arteries are located more proximally, and the angles at which these vessels originate are greater than in adults.
- The radius of curvature of the arcs formed by the vessels changes. Thus, in newborns and children under 12 years of age, the aortic arch has a larger radius of curvature than in adults.
- Partial change in the topography of blood vessels. How older child, the lower the aortic arch is located.
- Growth rate great vessels slower compared to the heart. So, if the volume of the heart increases 7 times by the age of 15, then the circumference of the aorta increases only 3 times.
- Over the years, the difference in the size of the lumen of the pulmonary artery and aorta decreases somewhat. At birth, the width of the aorta is 16 mm, the pulmonary artery is 21 mm, by 10-12 years their lumen is equal, and in adults the aorta has a larger diameter. Changes in arteries during physiological aging
The main change that occurs in the human arterial wall with physiological aging is a distinct progressive symmetrical thickening of the inner lining. This process is a consequence of the gradual accumulation of smooth muscle cells, mainly as a result of the movement of cells from the anterior membrane into this area and their subsequent proliferation, as well as the growth of additional connective tissue around them.
In the unaffected arterial wall, the content of lipids, mainly cholesteryl esters and phospholipids (in particular, sphingomyelin), also gradually increases with age. The synthesis of phospholipids also increases, which is probably a response to the increased need for the formation plasma membranes, as well as membranes for vesicles, lysosomes and other intracellular organelles. This is followed by a compensatory increase in the activity of all phospholipases, with the exception of sphingomyelinase. While most of phospholipids of the normal arterial wall are apparently a derivative of endogenous synthesis; cholesterol esters that accumulate with age are most likely of a plasmatic nature, since they contain mainly linoleic acid, the main fatty acid in plasma.
Moreover, using immunological methods, low-density lipoproteins (LDL) can be detected in the inner lining of normal arteries, and their content is directly proportional to their concentration in plasma. It was found that between the ages of 20 and 60 years, approximately 10 mg of cholesterol per 1 g of tissue accumulates in the inner lining. Thus, as a normal artery ages, smooth cells diffusely accumulate in the inner lining muscle cells And connective tissue, which leads to a progressive thickening of this layer. At the same time, progressive accumulation of sphingomyelin and cholesterol-linoleate occurs.
From a functional point of view, these age-related changes lead to a gradual increase in vascular stiffness. Large arteries may dilate, lengthen, or become tortuous. Aneurysms can form in the area of circular degenerative atherosclerotic plaques. Such deforming changes are often proportional to the diameter of the vessel and correlate with the presence of branches, bends and anatomical points of contact. The severity of the external supporting frame also determines the ability of vessels weakened due to loss of elasticity to withstand hydrostatic pressure. This is what makes brain vessels particularly vulnerable, deprived of environmental support.
Differentiation of branchial arteries. Age-related features of arteries in ontogenesis. Main changes in arteries during physiological aging.
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Reflecting a transition in progress phylogenesis from the gill circulation to the pulmonary circulation, in humans, in the process of ontogenesis, the aortic arches are first formed, which are then transformed into the arteries of the pulmonary and body circulation. 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). Ventral aortas go in an upward 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 the branchial arches develop at the head end of the embryo, the so-called aortic arch, or artery, is formed in each of them; these arteries connect the ventral and dorsal aortas on each side. Thus, in the region of the branchial arches, the ventral (ascending) and dorsal (descending) aortas are connected to each other using 6 pairs of aortic arches.
Subsequently, part of the aortic arches 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 noted above, is divided by the frontal septum into the ventral part, from which the pulmonary trunk is formed, and the dorsal part, which turns into the ascending aorta. This explains the location of the aorta behind the pulmonary trunk. It should be noted that the last pair of aortic arches along the blood flow, 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 aortic arch is preserved only on a small proximal segment, then the left one remains along its entire length, forming a ductus arteriosus, which connects the pulmonary trunk with the end of the aortic arch, which is important for the blood circulation of the fetus (see below). The fourth pair of aortic arches is preserved on both sides throughout its entire length, but gives rise to various vessels. The left 4th aortic arch, together with the left ventral aorta and part of the left dorsal aorta, form the aortic arch, arcus aortae.
Development of arteries.
Proximal segment of the right ventral aorta turns into the brachiocephalic trunk, truncus blachiocephalicus, the right 4th aortic arch - into the beginning of the right subclavian artery extending from the named trunk, a. subclavia dextra. The left subclavian artery arises from the left dorsal aorta caudal to the last aortic arch. The dorsal aortas in the area between the 3rd and 4th aortic arches 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 common carotid arteries, ah. carotides communes, and due to the above transformations of the proximal ventral aorta, the right common carotid artery turns out to arise from the brachiocephalic trunk, and the left one - directly from the arcus aortae. Further along the ventral aortas turn into the external carotid arteries, aa. carotides externae.
The third pair of aortic arches and the dorsal aortas in the segment from the third to the first branchial arch develop during internal carotid arteries, ah. carotides internae, bwm and explains that the internal carotid arteries lie more laterally in an adult than the external ones. The second pair of aortic arches turns into aa. linguales et pharyngeae, and the first pair - into the maxillary, facial and temporal arteries. When the normal course of development is disrupted, various anomalies occur.
Development of arteries.
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 intersegmental arteries. In the neck area, they are early connected on both sides of the body by a series of anastomoses, forming longitudinal vessels - vertebral arteries.
At the level of the 6th, 7th and 8th cervical intersegmental arteries, the kidneys of the upper extremities are formed. One of the arteries, usually the 7th, grows into upper limb and with the development of the hand increases, forming distal section subclavian artery (its proximal part develops, as already indicated, on the right from the 4th aortic arch, on the left it grows from the left dorsal aorta, with which the 7th intersegmental arteries connect).
Subsequently, the cervical intersegmental arteries are obliterated, as a result of which the vertebral arteries appear to arise from the subclavian ones.
The thoracic and lumbar intersegmental arteries give rise to the aa. intercostales posteriores and aa. lumbales.
Visceral arteries 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) develop into the main arteries of the limbs, others (along the n. medianus, n. ischiadicus) remain companions of the nerves. Based on materials from http://venus-med.ru/.
Reflecting a transition in progress phylogenesis from the gill circulation to the pulmonary circulation, in humans, in the process of ontogenesis, the aortic arches are first formed, which are then transformed into the arteries of the pulmonary and body circulation. In a 3-week fetus truncus arteriosus, leaving 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 the branchial arches develop at the head end of the embryo, the so-called aortic arch, or artery, is formed in each of them; these arteries connect the ventral and dorsal aortas on each side. Thus, in the region of the branchial arches, the ventral (ascending) and dorsal (descending) aortas are connected to each other using 6 pairs of aortic arches.
Subsequently, part of the aortic arches 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 noted above, is divided by the frontal septum into the ventral part, from which the pulmonary trunk is formed, and the dorsal part, which turns into the ascending aorta. This explains the location of the aorta behind the pulmonary trunk. It should be noted that the last pair of aortic arches along the blood flow, 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 aortic arch is preserved only on a small proximal segment, then the left one remains along its entire length, forming a ductus arteriosus, which connects the pulmonary trunk with the end of the aortic arch, which is important for the blood circulation of the fetus (see below). The fourth pair of aortic arches is preserved on both sides throughout its entire length, but gives rise to various vessels. The left 4th aortic arch together with the left ventral aorta and part of the left dorsal aorta form aortic arch, arcus aortae.
The proximal segment of the right ventral aorta turns into brachiocephalic trunk, truncus blachiocephalicus, right 4th aortic arch - to the beginning of the right subclavian artery extending from the named trunk, a. subclavia dextra. The left subclavian artery arises from the left dorsal aorta caudal to the last aortic arch. The dorsal aortas in the area between the 3rd and 4th aortic arches 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 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. Over the further course, the ventral aortas turn into external carotid arteries, aa. carotides externae.
The third pair of aortic arches and the dorsal aortas in the segment from the third to the first branchial arch develop during internal carotid arteries, aa. carotides internae, bwm and explains that the internal carotid arteries lie more laterally in an adult than the external ones. The second pair of aortic arches turns into ah. linguales et 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 a number of small paired vessels arise, running dorsally along 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 intersegmental 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 intersegmental 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 aortic arch, on the left it grows from the left dorsal aorta, with with which the 7th intersegmental arteries are connected).
Subsequently, the cervical intersegmental arteries are obliterated, as a result of which the vertebral arteries appear to arise from the subclavian ones.
Thoracic and lumbar intersegmental arteries give rise to ah. intercostales posteriores and aa. lumbales.
The visceral arteries of the abdominal cavity develop partly from ah. 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) develop into the main arteries of the limbs, others (along the n. medianus, n. ischiadicus) remain companions of the nerves.
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 gastrointestinal tract- celiac trunk, 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 scheme of the structure of the arteries of the embryo resembles vascular system animals with gill apparatus. Although all gill arteries cannot be simultaneously detected in a human embryo, since their development and restructuring take place in different time, 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. 148. Arteries of the wall of a 7-week embryo (according to Patten). 1 - main artery; 2 - vertebral artery; 3 - external carotid artery; 4 - superior intercostal artery; 5 - subclavian artery; 6 - aorta; 7 - seventh intercostal artery; 8 - posterior branch intercostal artery; 9 - first lumbar artery; 10 - inferior epigastric artery; 11 - middle sacral artery; 12 - sciatic artery; 13 - external iliac artery; 14 - umbilical artery; 15 - internal mammary artery; 16 - middle cerebral artery; 17 - internal carotid artery
Subsequently, the 3rd pair of aortic arches, the right and left dorsal aortas at a distance from the 3rd to the 1st branchial arches are transformed into the internal carotid arteries. Various blood vessels are formed from the 4th pair of aortic arches. The left 4th aortic arch, together with the left ventral and part of the dorsal aorta, turns into the aortic arch itself in the fetus. The 6th pair of aortic arches goes to build the right and left arteries, with the left pulmonary artery the fetus has an anastomosis with the aortic arch.
Rice. 149. Restructuring of arterial arches in embryos (according to Patten). a - diagram of the location of all aortic arches; b - early stage reconstruction 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 - top thyroid artery; 18 - lingual artery; 19 - maxillary artery; 20 - anterior inferior cerebellar artery; 21 - artery of the bridge; 22 - superior cerebellar artery; 23 - orbital 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.
From the right and left dorsal aortas and the common trunk, segmental arteries extend between the somites and then the sclerotomes in the lateral direction to supply blood to the corresponding segments of the spinal cord and surrounding tissues. Later, in the cervical region, the segmental arteries are reduced and only the vertebral arteries remain, which are branches of the subclavian arteries. The ventral group of blood vessels arising from the dorsal aorta is associated with the vessels of the yolk sac and intestinal tube. After the intestine is separated from the yolk sac, three arteries (celiac, superior mesenteric, inferior mesenteric) enter the intestinal mesentery.
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. 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. Through the right common cardinal vein, blood flows freely into the right atrium. Subsequently, the superior vena cava will form from this vein (Fig. 151). The left common cardinal vein is partially reduced, with the exception of its terminal part, which turns into the coronary sinus of the heart.
Fig. 151. Formation of the subcardinal sinus and its transformation into the inferior vena cava in a 7-week embryo (according to Patten). 1 - brachiocephalic vein; 2 - subcardinal-subcardinal anastomosis; 3 - gonad vein; 4 - ileal anastomosis; 5 - intersubcardinal anastomosis; 6 - supracardinal vein; 7 - inferior vena cava; 8 - subclavian vein; 9 - external jugular vein
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. Subcardinal veins at the level of the terminal kidney are connected venous anastomosis, which is 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 outflow 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 various options topography. 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. Anomalies in the development of the aortic arch are also expressed in the fact that it is not the left 4th aortic arch that reaches development, but the right one and the root of the dorsal aorta.
Severe circulatory disorders occur when the pulmonary veins (right and left) flow into the superior vena cava, into the left brachio-
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.
The left pulmonary artery, at the same level as the right artery, crosses the descending aorta and the left bronchus in front. In the gate of the left lung pulmonary the artery is located above the bronchus. It branches into the corresponding lobar and segmental arteries.
