Human Anatomy and Physiology (with Age-Related Characteristics of the Child's Body) - M.R. Sapin, V.I. Sivoglazov 2002

Splanchnology (The Study of the Viscera)
Angiology (The Study of the Vascular System)
Blood Vessels

The Cardiovascular system is divided into two circuits of Blood Circulation: the systemic (greater) and pulmonary (lesser) circuits (Fig. 78, see color insert). The pulmonary (lesser) circuit is involved in gas exchange between the blood and alveolar air, as its capillary networks surround the pulmonary alveoli. The systemic (greater) circuit delivers oxygen and nutrients to Organs and Tissues and removes carbon dioxide and Metabolic waste products from them.

Vessels of the Pulmonary Circulation

The pulmonary (lesser) circuit of circulation is formed by the pulmonary trunk, the right and left pulmonary Arteries and their branches, the capillary networks of the Lungs, and the right and left Pulmonary Veins with all their tributaries.

The pulmonary trunk, arising from the right ventricle of The Heart, carries deoxygenated blood to the lungs. The pulmonary trunk is 5–6 cm long and 3–3.5 cm in diameter; it runs upward and to the left, anterior to the initial part of the aorta. Beneath the aortic arch, at the level of the IV–V thoracic vertebrae, the pulmonary trunk bifurcates into the right and left pulmonary arteries, each of which runs to the corresponding lung.

The right pulmonary artery has a diameter of 2–2.5 cm; it is slightly longer than the left pulmonary artery and lies posterior to the ascending aorta and the SUPERIOR VENA CAVA. The left pulmonary artery runs toward the hilum of the lung, first upward, and then posteriorly and to the left. Each pulmonary artery, accompanying the Bronchi, branches into lobar, then segmental, and smaller arteries, down to the arterioles and capillaries that surround the alveoli.

The pulmonary veins, two for each lung (four veins in total), carry oxygenated blood from the lungs to the left atrium. The pulmonary veins, superior and inferior for both the right and left lungs, are formed by intraorgan veins of various orders. The smallest veins (venules) originate from capillaries closely adjacent to the walls of the pulmonary alveoli. The pulmonary veins run almost horizontally from the hilum of the lungs and open into the left atrium through separate orifices. The pulmonary veins do not have Valves.

Age-related Features of the vessels of the pulmonary circulation. In newborns, the circumference of the pulmonary trunk is larger than that of the aorta. After birth, due to the increased functional load, especially During the first year of life, the right and left pulmonary arteries and their branches in the lungs grow rapidly.

Arteries of the systemic circulation

The aorta, arising from the left ventricle of the heart, is located in the posterior part of the body along THE Vertebral Column (Fig. 79). The segment of the aorta, about 6 cm long, which directly emerges from The Heart and runs upward, is called the ascending aorta. The ascending aorta lies posterior to the pulmonary trunk and begins with a dilation called the aortic bulb. The right and left coronary arteries, which supply blood to the heart, branch off from the aortic bulb.

The ascending aorta arches to the left, transitioning into the aortic arch, which curves over the left main bronchus and continues as the descending aorta. Three large vessels branch off from the convex side of the aortic arch. On the right is the brachiocephalic trunk, and on the left are the left common carotid and left subclavian arteries.

The brachiocephalic trunk, about 3 cm long, arises from the aortic arch and runs upward and to the right. Posterior to the right sternoclavicular joint, the brachiocephalic trunk divides into the right common carotid and right subclavian arteries. The left common carotid and left subclavian arteries arise directly from the aortic arch, to the left of the brachiocephalic trunk.

The descending aorta is divided into two parts: the Thoracic Aorta and the Abdominal Aorta. The thoracic aorta lies on the vertebral column, to the left of the midline. Ten pairs of intercostal arteries arise from the thoracic aorta (the upper two originate from the Subclavian Artery system), along with the superior phrenic and visceral branches (bronchial, esophageal, pericardial, and mediastinal).

From the thoracic cavity, the aorta enters the Abdominal cavity through the aortic hiatus of the Diaphragm, becoming the abdominal aorta. At the level of the IV lumbar vertebra, where it divides into the two common iliac arteries (aortic bifurcation), the abdominal aorta continues as the thin median sacral artery, which corresponds to the caudal artery of mammals. Branching from the abdominal aorta from superior to inferior are the following arteries: the inferior phrenic, celiac trunk, superior mesenteric, middle suprarenal, renal, testicular (in males) or ovarian (in females), inferior mesenteric, and lumbar (4 pairs) arteries. The abdominal aorta supplies blood to the viscera located in the ABDOMINAL CAVITY AND to the abdominal walls.

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Fig. 79. The aorta and its major branches:

1 — ascending aorta, 2 — aortic arch, 3 — brachiocephalic trunk, 4 — right subclavian artery, 5 — right common carotid artery, 6 — left common carotid artery, 7 — left subclavian artery, 8 — thoracic aorta, 9 — posterior intercostal arteries, 10 — celiac trunk, 11 — superior mesenteric artery, 12 — left renal artery, 13 — abdominal aorta, 14 — left ovarian (testicular) artery, 15 — inferior mesenteric artery, 16 — left common iliac artery, 17 — left internal iliac artery, 18 — left external iliac artery, 19 — median sacral artery, 20 — right Ureter, 21 — right testicular (ovarian) artery, 22 — right Kidney, 23 — right renal artery, 24 — right Adrenal gland, 25 — right inferior phrenic artery

Arteries of the HEAD and Neck

The common carotid artery (paired, right and left) runs upward alongside the Trachea and Esophagus. At the level of the superior border of the thyroid Cartilage, it divides into the External Carotid Artery, which branches outside the cranial cavity, and the Internal Carotid Artery, which passes through the carotid canal into the Skull to supply the Brain.

The external carotid artery runs upward and, within the substance of the parotid gland, divides into its terminal branches: the maxillary and superficial temporal arteries.

The largest Anterior branches of the external carotid artery are the superior thyroid artery, which runs to The Thyroid Gland and Larynx; the lingual artery, supplying the Tongue and sublingual salivary gland; and the facial artery, which arches over the Base of the Mandible and runs to the Tissues of the angle of the Mouth, External Nose, medial angle of the eye, pharyngeal wall, Cytology/practical/98.html">Submandibular salivary gland, and palatine tonsil. Arising posteriorly from the external carotid artery are the occipital artery, which supplies the Skin and Muscles of the occiput, and the posterior auricular artery, which supplies the auricle and the walls of the external acoustic meatus. Medially, the ascending pharyngeal artery branches off from the external carotid artery and runs to the walls of the Pharynx.

The terminal Branches of the external carotid artery ascend. The superficial temporal artery runs to the soft tissues of the temporal region (skin, muscles). The maxillary artery passes deep into the face, entering the infratemporal and pterygopalatine fossae. It supplies the Muscles of Mastication, the upper and lower Teeth, the Hard and Soft palate, the walls of the Nasal cavity, and the dura mater.

The internal carotid artery, giving off no branches in the neck, runs upward to the base of the skull. It enters the cranial cavity through the carotid canal in the Temporal bone and, passing lateral to the sella turcica, gives off its terminal branches. One of the branches of the internal carotid artery, the ophthalmic artery, enters the Orbit along with the Optic nerve and supplies the Eyeball, its accessory structures (extraocular muscles, lacrimal gland, and other tissues), the nasal mucosa, and the dura mater. The anterior and middle cerebral arteries branch from the internal carotid artery to supply the brain. The right and left anterior cerebral arteries are connected by the short anterior communicating artery.

The right and left internal carotid arteries anastomose with the posterior cerebral arteries (branches of the Basilar artery) via the posterior communicating arteries, forming a closed arterial circle of the brain (circle of Willis) at the base of the brain (Fig. 80, see color insert).

The subclavian artery arises directly from the aortic arch on the left, and from the brachiocephalic trunk on the right; it then arches over the cervical Pleura and passes between the clavicle and the I rib, heading toward the axilla. The vertebral artery runs upward from the subclavian artery, passing through the foramina of the transverse processes of the cervical vertebrae and entering the cranial cavity through the foramen magnum. Within the cranial cavity, the vertebral artery joins its counterpart from the opposite side to form the basilar artery. Located on the Inferior surface of the Brainstem, the basilar artery, whose terminal branches are the posterior cerebral arteries, supplies the occipital and temporal lobes of the brain and participates in The formation of the cerebral arterial circle. The vertebral artery gives off lateral branches to the Spinal Cord and Cerebellum, while the basilar artery supplies the brainstem, cerebellum, and Inner ear.

The branches of the subclavian artery also include the internal thoracic artery, the thyrocervical trunk, the costocervical trunk, and the transverse cervical artery. The internal thoracic artery runs downward along the inner surface of the anterior thoracic wall (adjacent to the Sternum). The terminal branch of the internal thoracic artery, the superior epigastric artery, runs within the anterior abdominal wall down to the level of the umbilical ring. The internal thoracic artery gives off branches to the anterior PARTS OF THE intercostal spaces and supplies the Pericardium, diaphragm, pectoral muscles, Thymus, and mammary gland. The short thyrocervical trunk divides into four branches that run to the thyroid gland, larynx, pharynx, esophagus, trachea, and the muscles of the neck and scapula. The costocervical trunk gives off the two superior intercostal arteries, as well as branches to the Neck Muscles, spinal cord, and its Meninges. The transverse cervical artery gives off branches to the SUPERFICIAL MUSCLES OF the back and neck.

Arteries of the upper limb

The arteries of the upper limb include the axillary, brachial, radial, and ulnar arteries and their branches (Fig. 81, see color insert).

The axillary artery, which is a continuation of the subclavian artery, is located in the axillary cavity, where it gives off several large branches to the muscles of the shoulder girdle, the shoulder joint, and the mammary gland. These include the thoracoacromial, lateral thoracic, subscapular, and other arteries. At the level of the lower border of the pectoralis major Muscle, the axillary artery continues as the brachial artery.

The brachial artery is located on the medial side of the arm, in its medial bicipital groove near the biceps brachii muscle. The brachial vein and the median nerve lie adjacent to the brachial artery. In the cubital fossa, the brachial artery divides into the radial and ulnar arteries. Along the arm, the brachial artery gives off muscular branches, the superior and inferior ulnar collateral arteries (to the elbow joint), and a large branch—the deep artery of the arm (profunda brachii), which runs along with the radial nerve through the humeromuscular canal into the posterior compartment of the arm, where it supplies the triceps brachii muscle and the elbow joint. On the surface of the elbow Joint Capsule, the supplying arteries form an articular arterial network that provides collateral pathways for blood flow and ensures a constant Blood supply to the joint itself, as well as to the forearm and hand.

The radial and ulnar arteries run in their respective grooves on the forearm. Through their muscular and other branches, these arteries supply blood to the skin, muscles, and bones, and also give off major branches to both the elbow and wrist joints. The radial artery, located superficially in the distal (lower) part of the forearm, is commonly used to feel the pulse.

Upon entering the hand, the radial and ulnar arteries and their branches anastomose to form the superficial and deep palmar arches. Both palmar arches ensure a constant, even blood flow to the hand. Arteries supplying the fingers, skin, muscles, bones, and JOINTS OF THE hand arise from these superficial and deep palmar arches.

The thoracic aorta and its branches

The thoracic aorta is located in the posterior Mediastinum, to the left of the vertebral column. It gives off both parietal (wall) and visceral (organ) branches. The parietal branches include ten pairs of posterior intercostal arteries (the upper two originate from the subclavian artery system), which run into the soft tissues of the intercostal spaces to supply the thoracic walls and the upper part of the anterior abdominal wall. The thoracic aorta also gives off the superior phrenic arteries, which supply blood to the diaphragm. The visceral branches include the bronchial, esophageal, pericardial, and mediastinal branches.

After passing through the aortic hiatus of the diaphragm, the thoracic aorta continues as the abdominal aorta.

The abdominal aorta and its branches

The abdominal aorta is located on the posterior abdominal wall, anterior to the vertebral column, adjacent to the INFERIOR VENA CAVA, which lies to its right.

The abdominal aorta gives off parietal and visceral branches. The parietal branches include two inferior phrenic arteries running upward to the diaphragm and five pairs of lumbar arteries supplying the abdominal walls. The visceral Branches of the Abdominal Aorta are divided into unpaired and paired arteries. The Unpaired Visceral Branches of the abdominal aorta include the celiac trunk, the superior mesenteric artery, and the inferior mesenteric artery. The paired visceral branches are the middle suprarenal, renal, and testicular (ovarian) arteries.

Unpaired branches of the abdominal aorta. The celiac trunk is a short, thick vessel that arises from the aorta at the level of the 12th thoracic vertebra and divides into three large branches: the splenic, common hepatic, and left gastric arteries.

The splenic artery runs to the left along the upper border of the Pancreas toward the Spleen, which is located in the left hypochondrium.

Along its course, the splenic artery gives off short branches to the Stomach AND PANCREAS, as well as the left gastro-omental (gastroepiploic) artery to the greater curvature of The Stomach and the greater omentum. The second branch of the celiac trunk, the common hepatic artery, gives off a large branch—the gastroduodenal artery, which supplies the walls of the stomach, duodenum, and pancreas. The right gastro-omental (gastroepiploic) artery arises from this artery, running along the greater curvature of the stomach to anastomose with the left gastro-omental artery (a branch of the splenic artery). The common hepatic artery continues as the hepatic artery proper, which gives off a branch to the Gallbladder and enters the porta hepatis, where it branches into smaller arteries down to the capillaries. The right gastric artery arises from the hepatic artery proper and runs to the lesser curvature of the stomach. The third branch of the celiac trunk, the left gastric artery, runs toward the left side of the lesser curvature of the stomach, where it turns right and anastomoses with the right gastric artery. Thus, the stomach is supplied by branches of the large right and left gastric, and right and left gastro-omental arteries, which originate from the celiac trunk and form arterial arches along the lesser and greater curvatures of the stomach (Fig. 82).

The superior mesenteric artery arises from the abdominal aorta just below the celiac trunk and enters the mesentery of the Small Intestine. The inferior pancreaticoduodenal artery runs from the superior mesenteric artery to the duodenum and the head of the pancreas, where it anastomoses with the superior pancreaticoduodenal artery (a branch of the gastroduodenal artery). The superior mesenteric artery gives off numerous (16–20) intestinal (jejunal and ileal) arteries, as well as the ileocolic artery to the terminal ileum, cecum, and Appendix. The right colic artery (to the ascending colon) and the middle colic artery (to the transverse colon) also originate from the superior mesenteric artery.

Fig. 82. Arteries of the stomach. Celiac trunk:

1 — celiac trunk, 2 — aorta, 3 — left gastric artery, 4 — stomach, 5 — spleen, 6 — splenic artery, 7 — left gastro-omental artery, 8 — greater omentum, 9 — right gastro-omental artery, 10 — pancreas, 11 — inferior vena cava, 12 — portal vein, 13 — gastroduodenal artery, 14 — common Bile duct, 15 — right gastric artery, 16 — common hepatic artery, 17 — right lobe of the Liver, 18 — hepatic artery proper, 19 — gallbladder, 20 — left lobe of the liver

The inferior mesenteric artery arises from the left side of the abdominal aorta at the level of the third lumbar vertebra. Running downward and to the left, the inferior mesenteric artery gives off several branches: the left colic, sigmoid, and superior rectal arteries.

The left colic artery runs to the left, giving off branches to the descending colon and the left part of the transverse colon.

The sigmoid arteries (2–3) run to the sigmoid colon between the layers of its mesentery.

The superior rectal artery, which is the terminal branch of the inferior mesenteric artery, runs downward and branches within the walls of the upper rectum.

Anastomoses exist between all the colic and sigmoid arteries, running along the inner margin of all parts of the colon.

Paired branches of the abdominal aorta. The middle suprarenal artery, a paired vessel, arises from the abdominal aorta below the celiac trunk and runs laterally to the adrenal (suprarenal) gland. The middle suprarenal artery anastomoses with the superior suprarenal arteries (branches of the inferior phrenic artery) and the inferior suprarenal artery (arising from the renal artery of the same side).

The renal artery, paired, arises from the aorta at the level of the second lumbar vertebra and courses toward the renal hilum. The right renal artery is longer than the left and passes behind the inferior vena cava. At the renal hilum, the renal artery divides into branches entering the renal parenchyma. The inferior suprarenal artery is a branch of the renal artery.

The testicular (ovarian) artery, a paired long vessel, arises below the renal artery and courses downward into the lesser pelvis to the Ovary in females, or to the Testis in males within the Spermatic Cord.

Arteries of the pelvis

The terminal branches of the abdominal aorta are the thin median sacral artery, as well as the large, thick right and left common iliac arteries, into which the aorta divides at the level of the fourth lumbar vertebra.

The common iliac artery (paired) runs retroperitoneally along the medial border of the psoas major muscle. At the level of the sacroiliac joint, each common iliac artery divides into the internal and external iliac arteries.

The internal iliac artery descends into the lesser pelvis along its wall and, at the level of the greater sciatic foramen, divides into parietal and visceral branches.

The Parietal branches of the internal iliac artery include the iliolumbar, lateral sacral, obturator, and superior and inferior gluteal arteries.

The iliolumbar artery courses superiorly, laterally, and posteriorly, giving off branches to the psoas and iliacus muscles, the quadratus lumborum muscle, as well as to the pelvic bones and the spinal cord.

The lateral sacral artery supplies blood to the sacrum and its adjacent soft tissues.

The obturator artery passes through the obturator canal (along with the obturator nerve) to the thigh, where it gives off branches to the hip joint and the adductor muscles of the thigh.

The superior gluteal artery leaves the pelvic cavity through the suprapiriform foramen into the gluteal region to supply the gluteus medius and minimus muscles.

The inferior gluteal artery leaves the pelvic cavity through the infrapiriform foramen to supply the gluteus maximus muscle.

The Visceral Branches of the internal iliac artery include the umbilical, inferior vesical, uterine (in females), internal pudendal, and middle rectal arteries.

The umbilical artery courses along the lateral surface of the Urinary Bladder toward the umbilical ring along the posterior surface of the anterior abdominal wall. In the fetus, this artery carries venous blood to the Placenta, whereas in adults, it is almost entirely obliterated, remaining patent only in its proximal portion. This artery gives off branches to the urinary bladder (superior vesical arteries), the ureter, and the Ductus deferens (in males).

The inferior vesical artery courses to the urinary bladder, giving off branches along its path to the prostate and Seminal Vesicle (in males), and to the Vagina (in females).

The uterine artery runs to the Uterus between the layers of the broad ligament of the uterus and gives off branches to the ovary and vagina.

The middle rectal artery supplies the middle portion of the rectum, anastomosing with the superior and inferior rectal arteries.

The internal pudendal artery first exits the lesser pelvic cavity through the infrapiriform foramen (along with the inferior gluteal artery), then curves around the ischial spine and enters the ischioanal fossa through the lesser sciatic foramen, where it gives off the inferior rectal artery (to the rectum), the perineal artery (to the MUSCLES AND FASCIAE of the Perineum), and branches to the external genitalia.

The branches of the internal iliac artery form arterial anastomoses with neighboring arteries, providing collateral circulation in the pelvic Arterial System.

The external iliac artery runs along the medial border of the psoas major muscle to the inguinal ligament, beneath which it continues onto the thigh as the femoral artery. Along its course from its origin to the inguinal ligament, two large branches arise from the external iliac artery. The first is the inferior epigastric artery, which courses superiorly into the anterior abdominal wall, where it gives off lateral branches to the muscles and pubic bone, and anastomoses with branches of the superior epigastric artery (from the internal thoracic artery). The second branch of the external iliac artery is the deep circumflex iliac artery, which supplies the iliacus, transversus abdominis, and internal oblique muscles of the abdomen, as well as the tensor fasciae latae muscle.

Arteries of the lower limb

The arteries of the lower limb include the femoral, popliteal, anterior and posterior tibial, and fibular arteries and their branches (Fig. 83, see color insert).

The femoral artery, which is the continuation of the external iliac artery, lies lateral to the femoral vein within the vascular lacuna. The femoral artery then descends through the femoral triangle, situated between the Superficial layer of the fascia lata anteriorly and the deep layer posteriorly. Next, the artery passes through the adductor canal and enters the popliteal fossa, where it becomes the popliteal artery. The branches of the femoral artery are the superficial epigastric artery, the superficial circumflex iliac artery, the external pudendal arteries, the descending genicular artery, and the deep artery of the thigh.

The superficial epigastric artery courses superiorly within the subcutaneous tissue of the anterior abdominal wall.

The superficial circumflex iliac artery runs laterally along the inguinal ligament toward the anterior superior iliac spine, supplying the skin and the tensor fasciae latae muscle.

The branches of the external pudendal arteries supply blood to the corresponding organs.

The descending genicular artery emerges through the anterior wall of the adductor canal and courses downward to the knee joint.

The profunda femoris (deep artery of the thigh) is the largest branch of the femoral artery. It courses deep, giving off the medial and lateral circumflex femoral arteries (which supply the thigh muscles) and three perforating arteries that pass into the posterior region of the thigh, where they branch into the muscles and skin of this area.

The popliteal artery is the direct continuation of the femoral artery. It lies posteriorly against the capsule of the knee joint. At the level of the lower border of the popliteus muscle, it divides into its terminal branches: the anterior and posterior tibial arteries. Within the popliteal fossa, the popliteal artery gives off five large branches to the knee joint: the lateral and medial superior genicular, the middle genicular, and the lateral and medial inferior genicular arteries. Together with the descending genicular artery (from the femoral artery) and other arteries, these vessels form the genicular anastomotic network, which provides collateral circulation around the knee joint.

The anterior tibial artery, one of the terminal branches of the popliteal artery, enters the anterior compartment of the leg through an opening in the interosseous membrane. The anterior tibial artery gives off the anterior and posterior tibial recurrent arteries to the knee joint, muscular branches, and the lateral and medial anterior malleolar arteries to the corresponding malleoli and the ankle joint. The terminal branch of the anterior tibial artery is the dorsalis pedis artery. Passing deep to the extensor retinaculum, this artery courses toward the first intermetatarsal space, where it turns laterally to become the arcuate artery, which gives off lateral branches. The arcuate artery gives rise to the dorsal metatarsal arteries, which divide into the dorsal digital arteries.

The posterior tibial artery is the second terminal branch of the popliteal artery. It courses through the cruropopliteal canal deep to the triceps surae muscle. Running downward and inclining medially, the posterior tibial artery passes behind the medial malleolus to reach the FOOT. In the posterior compartment of the leg, the artery gives off muscular branches, a large branch called the fibular (peroneal) artery, which runs laterally to the corresponding muscles, and medial malleolar branches. The fibular artery gives off lateral malleolar branches to the lateral malleolus. The posterior tibial artery curves behind and below the medial malleolus and, passing deep to the flexor retinaculum, enters the SOLE OF THE foot, where it divides into the medial and lateral plantar arteries.

The medial plantar artery runs in the medial plantar sulcus and gives off muscular branches and proper digital arteries to the First and Second toes. The lateral plantar artery is the terminal branch of the posterior tibial artery. It courses through the lateral plantar sulcus, then curves medially to form the plantar arch. The plantar arch gives off muscular and cutaneous branches, as well as plantar metatarsal and plantar digital arteries to the second through fifth toes.

Age-Related Features of Arteries and the Microcirculatory Bed

After birth, as a child grows, the circumference, diameter, wall thickness, and length of the arteries increase. The level at which arterial branches originate from the main arteries, and even their branching pattern, also change. The diameter of the left coronary artery is larger than that of the right coronary artery in people of all age groups. The most significant differences in the diameter of these arteries are observed in newborns and children aged 10—14 years. In individuals over 75 years of age, the diameter of the right coronary artery is slightly larger than that of the left. The diameter of the common carotid artery in young children is 3—6 mm, whereas in adults it is 9—14 mm; the diameter of the subclavian artery increases most rapidly from birth to 4 years of age. During the first 10 years of life, the middle cerebral artery has the largest diameter of all cerebral arteries.

In early childhood, the intestinal arteries are almost all of equal size. The difference between the diameter of the main arteries and the diameter of their second- and third-order branches is initially small; however, as the child grows, this difference also increases. The diameter of the main arteries grows faster than that of their branches. During the first 5 years of a child's life, the diameter of the ulnar artery increases more rapidly than that of the radial artery, but subsequently, the diameter of the radial artery predominates. The circumference of the arteries also increases. For instance, the circumference of the ascending aorta is 17—23 mm in newborns, 39 mm at 4 years of age, 49 mm at 15 years, and 60 mm in adults.

The wall thickness of the ascending aorta increases very rapidly up to 13 years of age, while that of the common carotid artery stabilizes after 7 years. The luminal area of the ascending aorta increases dramatically—from 23 mm² in newborns to 107 mm² in 12-year-olds, which is consistent with the increase in heart size and Cardiac Output.

The length of the arteries increases proportionally to the growth of the body and limbs. For example, the length of the descending aorta increases fourfold by age 50, with the thoracic part growing faster than the abdominal part. The arteries supplying the brain develop most intensively up to

3—4 years of age, outstripping other vessels in growth rate. The anterior cerebral artery increases in length most rapidly. With age, the arteries supplying the Internal Organs, as well as the arteries of the upper and lower limbs, also elongate. For example, in newborns and infants, the inferior mesenteric artery is 5—6 cm long, whereas in adults it is 16—17 cm.

The levels at which branches originate from the main arteries in newborns and children are generally located more proximally, and the branching angles of these vessels are wider in children than in adults. The radius of curvature of the arches formed by the vessels also changes. For example, in newborns and children under 12 years of age, the aortic arch has a larger radius of curvature than in adults.

In proportion to the growth of the body and limbs, and the corresponding increase in arterial length, partial Changes in the topography of these vessels occur. The older a person is, the lower the aortic arch is situated. In newborns, the aortic arch lies above the level of the first thoracic vertebra (I); at 17—20 years, it is at the level of II; at 25—30 years, at the level of III; at 40—45 years, at the level of IV; and in elderly and senile individuals, it is at the level of the intervertebral disc between the IV and V thoracic vertebrae.

The Topography of the limb arteries also changes. For example, in a newborn, the PROJECTION OF THE ulnar artery corresponds to the anteromedial border of the ulna, and that of the radial artery to the anteromedial border of the radius. With age, the ulnar and radial arteries shift laterally relative to the midline of the forearm. In children over 10 years of age, these arteries are situated and projected in the same way as in adults. The projection of the femoral and popliteal arteries during the first years of a child's life also shifts laterally from the midline of the thigh. Consequently, the projection of the femoral artery approaches the medial border of the Femur, while the projection of the popliteal artery approaches the midline of the popliteal fossa. A change in the topography of the palmar arches is also observed. In newborns and young children, the superficial palmar arch is located proximal to the middle of the II and III Metacarpal bones, whereas in adults it projects at the level of the middle of the III metacarpal bone.

As age increases, the branching pattern of the arteries also changes. For instance, in newborns, the coronary arteries exhibit a distributive branching pattern, but by 6—10 years of age, a main-trunk pattern is established, which persists throughout life.

The formation, growth, and tissue Differentiation of the intraorgan vascular bed (small arteries and veins) in various human organs proceed unevenly during ontogeny. By the time of birth, the walls of the arterial segment of intraorgan vessels, unlike the venous segment, possess three tunics: the tunica externa (adventitia), media, and intima. After birth, the length and diameter of intraorgan vessels increase, as do the number of intervascular anastomoses and the vascular density per unit of organ volume. This process occurs most intensively during the first year of life and between the ages of 8 and 12.

By the time of birth, the Blood vessels of the microcirculatory bed are equipped with specialized mechanisms that regulate blood flow. One such mechanism is the precapillary sphincters, which are accumulations of smooth muscle Cells at the Water/144.html">Origin of the capillaries. Age-related changes in the human microcirculatory bed in different organs and tissues proceed depending on the timing of the functional maturation of these organs' structures.

Review and Self-Assessment Questions:

1. List the blood vessels that form the pulmonary (lesser) circulation and state its Functions.

2. Name the Branches of the aortic arch and their functions. To which parts of the body do the major branches of the aorta course?

3. Name the branches of the external and internal carotid arteries. Which organs do these branches supply with blood?

4. Name the arteries that form the cerebral arterial circle (circle of Willis) at the base of the brain.

5. Name the arteries of the upper limb and their areas of distribution. Which arteries participate in the Formation of the palmar arterial arches?

6. List the branches of the thoracic and abdominal aorta. To which organs do these arteries run?

7. Name the branches of the internal and external iliac arteries and the organs they supply.

8. List the arteries of the lower limb and the regions they supply.

9. Name the arteries located on the dorsal and plantar surfaces of the foot. What branches do these arteries give off?