Human Anatomy (with Fundamentals of Dynamic and Sports Morphology) - Ivanitsky M. F. 2008

The Study of the Heart and Blood Vessels
The Heart

The shape of The Heart is typically compared to an irregular cone, with its base directed posteriorly, to the right, and upward, and its apex pointing anteriorly, to the left, and downward.

The heart consists of four chambers: two ventricles—right and left—and two atria—right and left. The heart has an anterior, or sternocostal, surface, a posterior, or diaphragmatic, surface, and right and left borders.

The anterior surface faces forward and somewhat upward and is formed mainly by the wall of the right ventricle and, to a lesser extent, the left ventricle. The inferior surface faces backward and downward toward the Diaphragm and is formed by the wall of the left and, in part, the right ventricles, as well as the atrial walls. The left, obtuse border is formed mainly by the left ventricle, while the right, acute border is formed by the right ventricle (Fig. 91).

The heart is located in the Mediastinum. Most of it lies in the left half of the body, and a smaller part in the right. The apex of the heart lies at the level of the 5th left intercostal space, slightly medial to the vertical line passing through the nipple or the midpoint of the clavicle. The left border of the heart runs obliquely to its apex from the junction of the Cartilage and bone of the 3rd rib; the right border, appearing as a curve to the right, projects 1–2 cm beyond the right margin of the Sternum at the level of the 3rd to 5th Ribs; the upper border lies at the level of the cartilages of the third ribs, and the lower border extends from the cartilage of the 5th right rib to the apex of the heart.

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Fig. 91. The heart (anterior view):

1 — brachiocephalic trunk; 2 — left common carotid a.; 3 — left subclavian a.; 4 — transition of the Pericardium into the epicardium; 5 — ligamentum arteriosum; 6 — pulmonary trunk; 7 — left auricle; 8 — left atrium; 9 — anterior interventricular sulcus with Blood Vessels; 10 — left ventricle; 11 — apex of the heart; 12 — right ventricle; 13 — coronary sulcus; 14 — right atrium; 15 — conus arteriosus; 16 — right auricle; 17 — aorta; 18 — SUPERIOR VENA CAVA

The fibrous Skeleton of the heart, to which the fibers of the muscular layer of its wall attach, consists of the fibrous rings located between the atria and ventricles.

The wall of the heart consists of three layers. The inner layer is called the endocardium, the middle is the myocardium, and the outer is the epicardium.

The endocardium is a thin membrane of endothelial Cells situated on a Connective Tissue layer containing elastic fibers and smooth Muscle cells. The myocardium is the thickest layer and largely determines the thickness of the heart wall. It is composed of Cytology/cytology/34.html">Cardiac Muscle tissue, which is striated but differs from Skeletal Muscle in several ways (see p. 38). Functionally, this tissue is closer to smooth muscle than to Striated skeletal muscle, as its contraction is involuntary. The epicardium, or the visceral layer of the serous pericardium, is a serous membrane made of connective tissue and covered on its free surface by mesothelium. The epicardium is firmly adherent to the myocardium. In the region of the cardiac sulci, where the Blood vessels of the heart run, fat deposits can often be observed beneath the epicardium.

The walls of the ventricles are significantly thicker than those of the atria. The wall of the left ventricle is much thicker than that of the right ventricle. This feature is due to the varying thickness of the muscular layer and is closely related to the function performed by the different Chambers of the heart.

These functional features become clear when considering the direction of blood flow throughout the entire Circulatory system. Blood from the systemic Circulation enters the right atrium, from where, due to the contraction of its walls and the simultaneous relaxation of the right ventricular walls, it flows into the right ventricle. Contraction of the heart is called systole, and relaxation is diastole. During ventricular systole, blood is pumped from the right ventricle into the Pulmonary Circulation, from which it enters the left atrium. When the left atrium contracts, blood passes into the left ventricle, and during left ventricular systole, it is ejected into the systemic circulation. Since the left ventricle has to overcome high resistance, its walls are thicker than those of the other heart chambers.

The muscular layer of the ventricular walls differs from that of the atrial walls not only in thickness but also in the arrangement of the muscle fibers. The ventricular wall has three layers of muscle fibers. The superficial (outer) layer of one ventricle runs downward from the fibrous rings and somewhat obliquely toward the apex of the heart, where it forms a vortex and transitions into the Deep Layer of the other ventricle, which ascends to its fibrous ring. Between the superficial and deep layers lies a middle circular layer, which is separate for each ventricle.

The muscular layer of the atrial walls is simpler in Structure. The atrial wall consists of two layers of fibers: a deeper layer, separate for each atrium, which forms circular bundles around the orifices of the Veins, and a superficial, transverse layer that encompasses both atria.

Between the right and left ventricles lies a massive septum composed of muscular tissue. Only a small area in its upper portion is made of connective tissue, which is why the entire interventricular septum is divided into muscular and membranous (tendinous) parts. The interatrial septum is composed of connective tissue (Fig. 92).

At the level of the bases of the great vessels, the epicardium reflects to become the pericardial sac, known as the parietal layer of the serous pericardium or simply the parietal pericardium. Between the pericardium and epicardium lies a slit-like space called the pericardial cavity.

The structure of the parietal pericardium and the epicardium is identical. On the outside, the parietal pericardium is tightly covered by fibrous tissue, which forms the fibrous pericardium. Together, the fibrous and serous pericardia form the pericardial sac that encloses the heart.

On the surface of the heart are sulci (grooves) through which blood vessels, Lymphatic vessels, and nerves pass. It is customary to distinguish two interventricular (longitudinal) sulci (anterior and posterior) and one coronary sulcus, which runs at the level of the fibrous rings of the heart (see Fig. 91).

The right atrium serves as the entry point for the venae cavae and the VEINS OF THE Heart itself. It has an additional space formed by the right auricle. Within the wall of the auricle, The cardiac muscle forms roughly parallel muscular ridges called pectinate Muscles (Fig. 92). Near the opening of the INFERIOR VENA CAVA, There is a small valve, which is its leaflet. On the inner wall of the right atrium, there is the fossa ovalis (in the fetus, this is an opening); arising from the ascending aorta are the right and left coronary Arteries, which provide the Blood supply to the heart.

Fig. 92. The heart (section through the ventricles and atria):

1 - ascending aorta; 2 - left atrium; 3 - aortic valve; 4 - anterior cusp of the left atrioventricular valve; 3 - posterior cusp of the left atrioventricular valve; 6 - papillary mm. of the left ventricle; 7 - trabeculae carneae; 8 - muscular part of the interventricular septum; 9 - papillary m. of the right ventricle; 10 - endocardium of the right ventricle; 11 - cusps of the right atrioventricular valve; 12 - right coronary a. in section; 13 - opening of the small cardiac v.; 14 - pectinate mm.; 15 - valve of the inferior vena cava; 16 - inferior vena cava; 17 - membranous part of the interventricular septum; 18 - chordae tendineae

Fig. 93. Arteries of the human body:

1 - superficial temporal a.; 2 - facial a.; 3 - left common carotid a.; 4 - left subclavian a.; 5 - axillary a.; 6 - brachial a.; 7 - deep artery of the arm; 8 - renal a.; 9 - Abdominal Aorta; 10 - testicular or ovarian a.; 11 - common iliac a.; 12 - external iliac a.; 13 - femoral a.; 14 - anterior tibial a.; 15 - dorsalis pedis a.; 16 - posterior tibial a.; 17 - fibular a.; 18 - popliteal a.; 19 - deep artery of the thigh; 20 - superficial palmar arch; 21 - deep palmar arch; 22 - ulnar a.; 23 - interosseous a.; 24 - radial a.; 25 - right subclavian a.; 26 - aortic arch; 27 - brachiocephalic trunk

The aortic arch lies behind the manubrium of the sternum and arches over the left bronchus. Anterior to it are the Thymus gland and adipose tissue. Three large arteries arise from the upper aspect of the aortic arch: the brachiocephalic trunk, the left common carotid, and the left subclavian, while branches to the Trachea and Bronchi arise from its lower aspect.

The brachiocephalic trunk lies anterior to the trachea and, ascending upward and to the right, divides at the level of the right sternoclavicular joint into the right common carotid and right subclavian arteries.

The right and left common carotid arteries differ in their initial course, with the left artery being longer than the right. Emerging through the superior thoracic aperture, they pass posterior to the sternocleidomastoid muscles. Lateral to each artery lie the Internal jugular vein and the Vagus nerve, while medial to them are the trachea, Esophagus, and Thyroid Gland. The common carotid arteries lie on the Deep Muscles of the Neck, adjacent to the anterior tubercles of the transverse processes of the 5th and 6th cervical vertebrae. In the event of injury to the common carotid artery or its branches, it can be compressed against these tubercles to control bleeding. The common carotid arteries do not give off any branches along their course. At the level of the superior border of the thyroid cartilage within the carotid triangle, each artery divides into the external and internal carotid arteries, forming dilations at this site known as the carotid sinuses.

In its initial segment, the External Carotid Artery lies relatively superficially within the carotid triangle and is covered by the Skin, platysma, and fascia. Its pulsation can be easily felt here. Ascending upward, the artery reaches the level of the neck of the Mandible, where it divides into its terminal branches: the superficial temporal and maxillary arteries (Fig. 94). Along its course, the external carotid artery gives off numerous branches, the largest of which are listed below.

The superior thyroid artery descends and supplies branches to the thyroid and Parathyroid glands, the Larynx, and the cricothyroid and sternocleidomastoid muscles.

The lingual artery courses into the substance of the Tongue, contributing to its blood supply.

The facial artery passes anteriorly beneath the digastric muscle and, curving around the mandible anterior to the masseter muscle, courses toward the medial angle of the eye. Along its path, it supplies branches to the soft Tissues of the face, including the upper and lower Lips and the Muscles of facial expression, anastomosing at the medial angle of the eye with Branches of the ophthalmic artery. The facial artery is easily palpable where it arches over the inferior border of the mandible.

Fig. 94. Main branches of the external carotid artery:

1 - branches of the superficial temporal a. to the frontal and parietal regions; 2 - superficial temporal a.; 3 - occipital a.; 4 - external carotid a.; 5 - internal carotid a.; 6 - common carotid a.; 7 - maxillary a.; 8 - facial a.

The ascending pharyngeal artery contributes to the blood supply of the Pharynx.

The occipital artery courses to the occipital region, ascending along the Occipital bone, where its pulsation can be felt, and reaches the parietal bones.

The superficial temporal artery is located anterior to the external acoustic meatus, where it is easily palpable. It supplies branches to the parotid gland, the muscles and skin of the face, and the auricle. In the temporal region, this artery, in turn, divides into branches supplying the frontal and parietal Regions of the HEAD. The course of these branches (especially the frontal branch) is often clearly visible under the skin, and their pulsation is easily felt.

The maxillary artery, arising from the external carotid artery and winding around the medial side of the neck of the mandible, lies on the belly of the lateral pterygoid muscle and courses toward the pterygopalatine fossa, where it divides into terminal branches that reach the mucosa of the Nose and Mouth. Along its course, the maxillary artery gives off branches to the external acoustic meatus, the temporomandibular joint, the Middle ear, as well as to the mandibular Teeth and the mylohyoid muscle. Its largest branches include the following.

The inferior alveolar artery. It runs within the mandibular canal, giving off branches to the teeth, and emerges through the mental foramen to supply the muscles and skin of the chin and lower lip.

The middle meningeal artery. It enters the cranial cavity through the foramen spinosum of the Sphenoid bone, runs along the arterial grooves on the inner surface of the cranial vault bones, and supplies branches to the dura mater.

Arteries supplying the Muscles of Mastication (masseter, pterygoid, and temporal muscles), as well as the buccinator muscle, which belongs to the muscles of facial expression.

The posterior superior alveolar artery. It supplies the posterior maxillary teeth (the middle and anterior teeth receive blood from another branch of the maxillary artery, the infraorbital artery).

The infraorbital artery. It enters the Orbit through the inferior orbital fissure and, passing through the infraorbital canal, emerges onto the anterior surface of the face, giving off branches to the maxillary teeth along its course.

The Internal Carotid Artery courses toward the external carotid opening, lying lateral to the pharynx and medial to the internal jugular vein. It has no branches in the neck. After passing through the carotid canal, this artery runs lateral to the sella turcica along the carotid sulcus of the sphenoid bone, passes through the cavernous sinus of the dura mater, and upon exiting gives off the ophthalmic artery (which enters the orbital cavity through the optic canal), the posterior communicating artery (with which it anastomoses with the posterior cerebral artery, a branch of the Subclavian Artery via the vertebral and basilar arteries) (Fig. 95), a branch to the choroid plexus of the ventricles, and the anterior and middle cerebral arteries.

The anterior cerebral artery curves around the anterior aspect of the corpus callosum, while the middle cerebral artery runs deep within the lateral sulcus of the cerebrum.

Fig. 95. Arteries of the Base of the Brain:

1 - anterior communicating a.; 2 - branches to the Pons; 3 - abducens n.; 4 - facial n.; 5 - posterior cerebellar a.; 6 - posterior spinal a.; 7 - Cerebellum; 8 - anterior spinal a.; 9 - vertebral a.; 10 - anterior inferior cerebellar a.; 11 - occipital lobe of the cerebral hemispheres; 12 - basilar a.; 13 - posterior cerebral a.; 14 - superior cerebellar a.; 15 - oculomotor n.; 16 - posterior communicating a.; 17 - internal carotid a.; 18 - middle cerebral a.; 14 - frontal lobe; 20 - anterior cerebral a. (after Spalteholz)

The internal carotid artery forms numerous anastomoses.

On the right, the subclavian artery arises from the brachiocephalic trunk, and on the left, from the arch of the aorta. It arches over the 1st rib, against which it can be compressed if necessary. The subclavian artery passes through the interscalene space along with the Brachial Plexus, lying posterior to the anterior scalene muscle.

The following branches arise from the subclavian artery.

The internal thoracic artery runs downward along the margin of the sternum behind the costal cartilages. It anastomoses with the intercostal arteries, gives off branches to the mammary gland, pericardium, and diaphragm, and continues along the rectus abdominis muscle as the superior epigastric artery, which anastomoses with the inferior epigastric artery arising from the external iliac artery.

The vertebral artery arises near the medial border of the anterior scalene muscle and runs through the foramina of the transverse processes of the upper six cervical vertebrae. Piercing the atlanto-occipital membrane, it enters the cranial cavity through the foramen magnum. Resting on the clivus of the occipital bone, the right and left vertebral arteries unite to form a single vessel, the Basilar artery, which ascends and divides into its terminal branches, the posterior cerebral arteries.

The posterior cerebral artery, both right and left, anastomoses with the internal carotid artery, and its branch, the anterior cerebral artery, anastomoses with the corresponding artery of the opposite side via the unpaired anterior communicating artery (see Fig. 95). Thus, the cerebral arterial circle (circle of Willis) is formed at the base of the brain, providing a well-developed anastomosis between the internal carotid and vertebral arteries within the cranial cavity.

Along its course, the vertebral artery gives off branches to the Spinal Cord and Medulla Oblongata, while the basilar artery additionally supplies the cerebellum.

The thyrocervical trunk is a short, thick branch that divides into four arteries. Among these, the inferior thyroid artery passes posterior to the common carotid artery to The Thyroid Gland, the ascending cervical artery ascends along the deep Muscles of the neck, the superficial cervical artery runs laterally, and the transverse cervical artery goes to the scapular muscles.

The costocervical trunk gives off branches to the deep muscles of the neck and to the 1st and 2nd intercostal spaces.

Thus, the subclavian artery participates in the blood supply to the spinal cord and partly the brain, the muscles of the first two intercostal spaces, the rectus abdominis muscle, and partly the muscles of the suboccipital region, larynx, trachea, esophagus, thyroid and thymus glands, as well as the scapula, chest, back, and diaphragm.

The axillary artery is the continuation of the subclavian artery. It passes through the axilla, lying between the pectoralis minor and major muscles on one side and the scapular muscles on the other. This artery is surrounded by the brachial plexus. Along its course, it gives off branches to the shoulder girdle and the shoulder joint. Its continuation is the brachial artery.

The brachial artery gives off branches to the muscles and skin of the arm. It lies in the groove on the medial side of the biceps brachii muscle, where its pulsation can be easily felt, especially in the lower third of the arm. Blood pressure is most commonly measured by the pressure in the brachial artery. Entering the cubital fossa, this artery divides into its terminal branches: the ulnar and radial arteries (Fig. 96). It is accompanied by two brachial veins and the median nerve. Along its course, it gives off several muscular branches, the deep artery of the arm (profunda brachii), which runs with the radial nerve in the humeromuscular canal, and two ulnar collateral arteries (superior and inferior). The profunda brachii artery participates in the blood supply of the triceps brachii muscle and, through its terminal branches, in The formation of the anastomotic network of the elbow joint.

Fig. 96. Arteries of the right upper limb (in the left diagram, the forearm and hand are shown from the dorsal side; in the right, from the palmar side):

1 — common carotid a.; 2 — brachiocephalic trunk; 3 — subclavian a.; 4 — axillary a.; 5 — brachial a.; 6 — deep a. of the arm; 6a — arterial network of the elbow joint; 7 and 8 — radial a.; 9 — interosseous a.; 10 — ulnar a.; 11 — deep palmar arch; 12 — superficial palmar arch

The superior and inferior ulnar collateral arteries descend to give off branches to the adjacent muscles and the elbow joint.

The radial artery runs anterior to the radius. In its lower part, it lies superficially in the radial groove, lateral to the flexor carpi radialis, where it is easily palpable and can be compressed against the radius. Below the styloid process of the radius, the radial artery winds around the lateral aspect of the wrist to the dorsum of the hand, and, piercing the first intermetacarpal space, enters the palm, where it continues as the deep palmar arch lying on the Metacarpal bones and interosseous muscles. Along its course, the radial artery gives off numerous muscular branches, PALMAR AND DORSAL carpal branches, and the artery to the 1st digit (thumb).

The ulnar artery runs along the medial side of the anterior surface of the forearm. It courses in the ulnar groove and, upon reaching the wrist joint, lies medial to the pisiform bone. This artery gives off a deep branch that contributes to the deep palmar arch. Its main trunk continues as the superficial palmar arch, which lies directly beneath the palmar aponeurosis (see Fig. 96).

Both the ulnar and radial arteries have recurrent branches that participate in forming the anastomotic network of the elbow joint. Along its course, the ulnar artery gives off numerous muscular branches, the common interosseous artery (whose branches run anterior and posterior to the interosseous membrane), and the common palmar digital arteries arising from the superficial arch. These common digital arteries divide into the proper palmar digital arteries and anastomose with the metacarpal arteries, which are branches of the deep palmar arch.

The proper palmar digital arteries run along the lateral and medial sides of each digit and anastomose with each other, particularly in the region of the distal Phalanges.

The descending aorta extends from the level of the 4th thoracic to the level of the 4th lumbar vertebra and is, in turn, divided into two parts: the thoracic and the abdominal.

The Thoracic Aorta runs along THE Vertebral Column in the thoracic cavity, located in the posterior mediastinum. On the left, it is covered by the Pleura; to its right is the azygos vein, and to its right and posterior is the Thoracic duct. At the level of the 8th–9th vertebrae, the esophagus lies adjacent to its anterior surface, accompanying the aorta along almost its entire course. The thoracic aorta gives off visceral and parietal branches. The visceral branches supply the bronchi, esophagus, Lymph Nodes, and adipose tissue.

The parietal branches include the intercostal arteries, which consist of ten pairs running in the intercostal spaces along the lower borders of the 3rd to 12th ribs. Since the aorta is located slightly to the left of the median plane, the right intercostal arteries are longer than the left ones. At the level of the rib head, each artery divides into anterior and posterior branches, which supply blood to the intercostal muscles, back muscles, spinal cord, its Meninges, and the skin of the trunk.

After passing through the aortic hiatus of the diaphragm, the thoracic aorta becomes the abdominal aorta, which lies anterior and slightly to the left of the median plane of the lumbar vertebral bodies (Fig. 93).

The abdominal aorta begins at the level of the 12th thoracic vertebra. Its terminal branches are the right and left common iliac arteries. To its right lies the inferior vena cava, and anteriorly are the Internal Organs of the Abdominal cavity. The abdominal aorta gives off parietal branches to the walls of the ABDOMINAL CAVITY AND visceral branches to the internal organs.

The parietal Branches of the Abdominal Aorta are the inferior phrenic artery, the lumbar arteries, and the median sacral artery. The inferior phrenic artery is paired; it arises from the aorta at the level of the 12th thoracic vertebra, runs along the Inferior surface of the diaphragm, participating in its blood supply, and additionally gives off branches to the Adrenal gland and adipose tissue.

The lumbar arteries, numbering four pairs, run to the muscles of the posterior and lateral abdominal walls, corresponding to the intercostal arteries.

The median sacral artery is a continuation of the aorta and descends along the anterior surface of the sacrum to the coccyx, giving off branches to the muscles, bones, and partially to the pelvic viscera.

The arteries supplying the abdominal viscera—visceral branches—are divided into paired and unpaired. The paired arteries include the middle suprarenal, renal, and testicular (or ovarian) arteries.

The middle suprarenal artery runs to the adrenal gland.

The renal artery arises from the aorta at the level of the 1st lumbar vertebra, enters the renal hilum, and there divides into second-order arteries. The right renal artery passes behind the inferior vena cava and is longer than the left. A branch to the adrenal gland arises from each renal artery.

The testicular artery (or ovarian) arises from the aorta at the level of the 2nd lumbar vertebra and descends. In males, the testicular artery enters the Inguinal Canal and, as part of the Spermatic Cord, reaches the Testis and its Epididymis. In females, the ovarian artery gives off branches not only to the Ovary but also to the Uterus.

The Unpaired Visceral Branches of the abdominal aorta include (Fig. 97): the celiac trunk, the superior mesenteric artery, and the inferior mesenteric artery.

The celiac trunk arises from the aorta as a short, thick vessel at the level of the 12th thoracic or 1st lumbar vertebra and divides into three large arteries: the left gastric, common hepatic, and splenic arteries.

The left gastric artery runs upward and to the left toward the lesser curvature of The Stomach, giving off branches to the esophagus, stomach, and lesser omentum, and anastomoses with the right gastric artery.

The common hepatic artery, in turn, divides into three branches: the right gastric artery, which anastomoses with the corresponding artery of the left side and runs along the lesser curvature of the stomach; the hepatic artery proper, which runs to the porta hepatis, where it divides into right and left branches that supply The Liver and Gallbladder; and the gastroduodenal artery, which gives off branches to the Pancreas and duodenum. A branch of this artery, the right gastro-omental artery, runs along the greater curvature of the stomach, anastomosing with the corresponding artery of the left side.

Fig. 97. Diagram of anastomoses of the unpaired branches of the abdominal aorta:

1 — abdominal aorta; 2 — celiac trunk; 3 — left gastric a.; 4 — splenic a.; 5 — common hepatic a.; 6 — right gastric a.; 7 — right branch of hepatic a. proper; 8 — left branch of hepatic a. proper; 9 — cystic a.; 10 — gastroduodenal a.; 11 — right gastro-omental a.; 12 — left gastro-omental a.; 13 and 14 — anastomosis between the celiac trunk and the superior mesenteric a.; 15 — superior mesenteric a.; 16 — middle colic a.; 17 — right colic a.; 18 — ileocolic a.; 19 — appendicular a.; 20 — anastomosis between the right and left colic aa.; 21 — inferior mesenteric a.; 22 — left colic a.; 23 — sigmoid a.; 24 — superior rectal a.; 25 — common iliac a.; 26 — external iliac a.; 27 — internal iliac a.; 28 — middle rectal a. (after V. N. Tonkov)

The splenic artery runs to the Spleen. In addition, it gives off branches to the pancreas, stomach, and greater omentum, as well as the left gastro-omental artery.

The superior mesenteric artery arises at the level of the 1st lumbar vertebra, passes beneath the head of the pancreas, crosses anteriorly to the inferior part of the duodenum, and gives off numerous branches (see Fig. 97). Its branches supply the pancreas and duodenum, anastomosing with the corresponding arteries that arise from the gastroduodenal artery.

The following arteries arise from the superior mesenteric artery. The jejunal and ileal arteries, numbering about 20, run to their respective organs. They form numerous anastomoses in the form of arches with their convex sides facing the Small Intestine. Small branches arise from these arches to supply the intestinal walls.

The ileocolic artery gives off branches to the terminal ileum, the cecum, and the Appendix.

The right colic artery runs to the ascending colon.

The middle colic artery runs within the mesentery of the transverse colon, which it supplies with blood.

All of these arteries form well-defined anastomoses with one another.

The inferior mesenteric artery arises to the left from the abdominal aorta at the level of the 3rd lumbar vertebra. It gives off the following branches: the left colic artery to the descending colon, the sigmoid arteries to the sigmoid colon, and the superior rectal artery to the rectum.

At the level of the 4th lumbar vertebra, the abdominal aorta divides into its terminal branches: the right and left common iliac arteries, which run laterally and downward. In turn, each of these divides into the internal and external iliac arteries.

The internal iliac artery descends into the pelvic cavity and divides into numerous branches supplying the walls and viscera of the pelvis. It gives off the following parietal branches:

- the superior gluteal artery, which leaves the pelvic cavity above the piriformis muscle to supply the gluteus medius and minimus muscles;

- the inferior gluteal artery, which leaves the pelvic cavity below the piriformis muscle to supply the gluteus maximus muscle and the sciatic nerve.

In addition, the internal iliac artery gives rise to the iliolumbar artery supplying the muscles and spinal cord, the lateral sacral artery running along the pelvic surface of the sacrum, and the obturator artery. The latter passes through the obturator canal to the adductor muscles of the thigh and the hip joint.

The Visceral Branches of the internal iliac artery include the arteries supplying the Urinary Bladder, rectum, and, in females, the uterus (uterine artery) and external genitalia.

The latter also receive branches from the internal pudendal artery, which, after passing through the opening below the piriformis muscle, enters the perineal region through the lesser sciatic foramen. In addition, the umbilical artery branches off from the internal iliac artery, functioning only during fetal life (after birth, it obliterates into a ligament). However, the lumen in the proximal part of the umbilical artery does not obliterate and gives off branches to the superior part of the urinary bladder.

The uterine artery has a tortuous course. It runs toward the cervix and, ascending along the lateral margin of the uterus to its fundus, gives off branches not only to the uterus itself, but also to the Vagina, fallopian tube, and ovary.

The external iliac artery is located at the boundary between the greater and lesser pelvis. It runs along the Medial surface of the psoas muscle and passes beneath the inguinal ligament. A branch of this artery is the inferior epigastric artery, which ascends along the posterior surface of the rectus abdominis muscle and anastomoses with the superior epigastric artery—a branch of the internal thoracic artery arising from the subclavian artery (see Fig. 93). In addition, the external iliac artery gives off the deep circumflex iliac artery, which runs laterally toward the iliac crest. This artery passes posterior to the inguinal ligament and gives off branches to the transversus abdominis and iliacus muscles.

After passing beneath the inguinal ligament, the external iliac artery continues as the femoral artery (Fig. 98), which lies in the groove between the iliopsoas and pectineus muscles within the femoral triangle. It runs downward and slightly backward along the anterior femoral groove and, after passing through the adductor canal, becomes the popliteal artery located in the popliteal fossa. The branches of the femoral artery are: the superficial epigastric artery, supplying the skin and the external oblique muscle of the abdomen; the superficial circumflex iliac artery, also supplying the skin and the external oblique muscle of the abdomen; and the external pudendal arteries, supplying the external genitalia.

Fig. 98. Arteries of the right lower limb:

1 — abdominal aorta; 2 — testicular a.; 3 — inferior mesenteric a.; 4 — common iliac a.; 5 — median sacral a.; 6 and 30 — external iliac a.; 7— internal iliac a.; 8 — lateral sacral a.; 9 — obturator a.; 10 — inferior epigastric a.;      11 — medial circumflex femoral a.; 12 — external pudendal a.; 13 — femoral a.; 14 — deep femoral a.; 15 — first perforating a.; 16 — entrance to the adductor canal; 17 — descending genicular a.; 18 — popliteal a.; 19 — medial superior genicular a.; 20 — anterior tibial a.; 21 and 24 — posterior tibial a.; 22 — fibular a.; 23 — perforating branch of the fibular a.; 25 — deep plantar branch; 26 — dorsal metatarsal a.; 27 — lateral tarsal a.; 28 — dorsalis pedis a.; 29 — iliac crest; 31 — 4th lumbar a. (after G. F. Ivanov)

The largest branch of the femoral artery is the deep artery of the thigh. It divides into the medial and lateral circumflex femoral arteries, the perforating arteries, and the descending genicular artery. The medial circumflex femoral artery gives branches to the hip joint and the adductor muscles of the thigh; the lateral circumflex femoral artery supplies the quadriceps femoris muscle; the perforating arteries supply the muscles of the posterior compartment of the thigh; the descending genicular artery participates in forming the arterial network of the knee joint.

The popliteal artery (see Fig. 98) is the direct continuation of the femoral artery. It runs downward along the posterior surface of the knee joint and gives off five branches: the lateral and medial superior, the lateral and medial inferior, and the middle genicular arteries. The popliteal artery also gives branches to the triceps surae muscle. The terminal branches of the popliteal artery are the posterior and anterior tibial arteries.

The posterior tibial artery passes anterior to the soleus muscle and descends within the cruropopliteal canal. It courses around the medial malleolus, where its pulsation is easily palpable, and passes onto the SOLE OF THE FOOT, dividing into the medial and lateral plantar arteries.

The posterior tibial artery gives off branches to the muscles of the posterior compartment of the leg and partly to the fibular muscles, as well as to the knee joint, participating in the formation of its arterial network.

The medial plantar artery runs toward the great toe and gives branches to the Medial Group of muscles on the plantar surface of the foot.

The lateral plantar artery runs obliquely in the lateral direction, then, turning toward the medial margin of the foot, continues into the plantar arch. The latter gives off four plantar metatarsal arteries, which run in the interosseous spaces and, at the base of the toes, divide first into common and then into proper plantar digital arteries, running to the distal phalanges along the medial and lateral sides of each toe.

The anterior tibial artery (see Fig. 98) passes through the interosseous membrane in the upper part of the space between the Tibia and Fibula and runs deep within the muscles of the anterior compartment of the leg. In the upper third of the leg, it lies between the tibialis anterior muscle and the extensor digitorum longus, and lower down, between the tibialis anterior muscle and the extensor hallucis longus. This artery gives branches to the knee joint, to the medial and lateral malleoli, and continues as the dorsalis pedis artery. The dorsalis pedis artery runs between the extensor hallucis longus and brevis muscles and gives off the deep plantar artery, which perforates the space between the 1st and 2nd Metatarsal Bones to anastomose with the plantar arch. In addition, along its course, the dorsalis pedis artery gives off the medial and lateral tarsal arteries and the arcuate artery, which runs along the dorsal aspect of the bases of the metatarsal bones. The pulsation of the dorsalis pedis artery is easily palpable.

Fig. 99. Veins of The Human Body (veins are shown with double-contour lines, arteries in black):

1 — facial v.; 2 — retromandibular v.; 3 — left internal jugular v.; 4 — left brachiocephalic v.; 5 — left subclavian v.; 6 — left axillary v.; 7 — cephalic v.; 8 — basilic v.; 9 — superior mesenteric v.; 10 — inferior vena cava; 11 — left common iliac v.; 12 — femoral v.; 13 — great saphenous v.; 14 — femoral a.; 15 — median cubital v.; 16 — brachial v.; 17 — superior vena cava; 18 — right

Three dorsal metatarsal arteries branch off from the arcuate artery, passing along the three middle dorsal interosseous muscles, and at the brachiocephalic v.; 19 — right subclavian v.; 20 — right internal jugular v. (after B. N. Uskov) bases of the toes, they divide into dorsal digital arteries.

There are several arterial networks in the lower limb: in the region of the greater trochanter, the hip joint, the knee joint, the lateral and medial malleoli, the calcaneus, and the dorsum of the foot. All the arteries passing near these structures participate in forming these networks.

Concluding the Overview of the Arterial System, it should be added that performing any Physical Exercise is associated with an increase in its activity. During exercise, the pulsation of the arteries becomes much more pronounced. The volume of blood entering the aorta from the heart with each contraction of its left ventricle increases, the lumen of the blood vessels, mainly capillaries, expands, and the blood supply to the organs improves. In addition, the blood supply to the walls of the blood vessels themselves, which supply these organs, is also enhanced. This is of positive significance for maintaining the Elastic properties of blood vessels, which typically decline with age.

Veins

All veins can be divided into three groups (Fig. 99):

— veins of the heart wall,

— veins of the superior vena cava system,

— veins of the inferior vena cava system, which also includes the PORTAL VEIN SYSTEM.

The veins of the heart wall collect blood distributed by the coronary artery system and drain into the right atrium either via the coronary sinus or independently.

The superior vena cava drains blood from the upper limbs, head, neck, and the walls of the thoracic and, partially, abdominal cavities. It is located in the thoracic cavity and is formed by the union of the right and left brachiocephalic veins, each of which, in turn, is formed by the union of the subclavian and internal jugular veins.

The superior vena cava runs from the level of the 1st rib (from its junction with the sternum) and drains into the right atrium at the level of the 3rd rib. The azygos vein and several mediastinal veins drain into the superior vena cava.

The azygos vein is the continuation of the right ascending lumbar vein and, in its lower portion, anastomoses with the inferior vena cava system (Fig. 100). The azygos vein receives the right intercostal veins, veins of the mediastinal organs, particularly the esophagus and bronchi, as well as the hemiazygos vein running on the left side, which is a continuation of the left ascending lumbar vein. The hemiazygos vein receives the left intercostal veins from the lower intercostal spaces (those from the upper spaces drain into the accessory hemiazygos vein). The anterior ends of the intercostal veins anastomose with the internal thoracic vein.

Several veins drain into the brachiocephalic veins, collecting blood from the thyroid gland, vertebral column, and intercostal spaces.

The junction of the internal jugular and subclavian veins is called the venous angle.

The internal jugular vein drains blood from the Organs of the Head and Neck. This vein begins at the jugular foramen and is a direct continuation of the transverse and sigmoid Dural Venous Sinuses. Along its course, it has two dilations—the superior and inferior bulbs, the superior being located in the region of the jugular foramen, and the inferior near its junction with the brachiocephalic vein. One to three Valves are located in the region of the inferior bulb. The internal and common carotid arteries, along with the accompanying internal jugular vein and vagus nerve, form the neurovascular bundle of the neck, which is enclosed in a common fascial sheath.

All veins draining into the internal jugular vein can be divided into two groups: intracranial and extracranial.

Intracranial veins include the dural venous sinuses and the veins of the brain, cranial bones, orbit, dura mater, and Inner ear that drain into them.    

The dural venous sinuses differ significantly from ordinary veins. Their walls are formed by the dura mater and contain elastic and fibrous fibers. Since there is no muscular layer, the lumen of the sinuses remains virtually constant. They are lined internally with endothelium but do not have valves. The most important sinuses are the superior and inferior sagittal, transverse, sigmoid, straight, and cavernous sinuses. Their Location and Structure are determined by the course of the dural folds (see p. 358).

Fig. 100. Diagram of anastomoses between the portal vein and the venae cavae:

1 — superior vena cava; 2 — right brachiocephalic v.; 3 — left brachiocephalic v.; 4 — subclavian v.; 5 — internal jugular v.; 6 — intercostal vv.; 7 — azygos v.; 8 — hemiazygos v.; 9 — esophageal venous plexus; 10 — liver; 11 — gastric vv. (left and right); 12 — portal v.; 13 — splenic v.; 14 — inferior mesenteric v.; 15 — superior mesenteric v.; 16 — renal v.; 17 — testicular (ovarian) v.; 18 — inferior vena cava; 19 — common iliac v.; 20 — superior rectal v.; 21 — left internal iliac v.; 22 — middle rectal v.; 23 — thoracoepigastric v.; 24 — internal thoracic v.; 25 — superior epigastric v.; 26 — superficial epigastric v.; 27 — inferior epigastric v.; 28 — paraumbilical v. (after V. N. Tonkov)

Diploic veins run through the cancellous bone of the cranial vault, communicating with both superficial veins and the dural venous sinuses. There are several direct connections between extracranial and intracranial veins—emissary veins, which pass through specific foramina in the cranial bones.

Most of the blood flowing through the dural venous sinuses is delivered by the cerebral veins, which run independently of the arteries and are divided into deep and superficial groups. The deep veins include, in particular, the great cerebral vein, which drains into the straight sinus. It collects blood mainly from the choroid plexuses of the Lateral ventricles, the thalamus, and the corpus striatum, and, like all cerebral veins, lacks valves. The superficial veins drain blood from the Cerebral Cortex AND empty primarily into the superior sagittal sinus.

Extracranial veins draining into the internal jugular vein include the pharyngeal, lingual, and thyroid veins, as well as the facial vein. The pharyngeal veins form a venous plexus located on its muscular layer. This plexus communicates with the veins of the vertebral column, palate, and deep Neck Muscles. The lingual veins accompany the lingual artery, and the superior thyroid veins accompany the superior thyroid arteries. The facial vein collects blood from the medial angle of the eye, forehead, orbital region, nose, as well as the upper and lower lips, cheek, and chin. In addition, it anastomoses with the veins of the orbit, soft palate, pharynx, muscles of mastication, upper and lower jaws, and the floor of the mouth.

The retromandibular vein (see Fig. 99) drains into the facial vein, collecting blood from the auricle, parietal and temporal regions, muscles of mastication, mandible, dura mater, and cranial bones.

Among the other veins of the neck, the largest are the external and anterior jugular veins.

The External Jugular Vein anastomoses with the retromandibular vein, runs down and slightly backward along the lateral side of the neck from the angle of the mandible, and drains into the venous angle, i.e., at the junction of the subclavian and internal jugular veins. The external jugular vein collects blood from the auricle, occiput, neck, nuchal region, and the superior aspect of the scapula. It is clearly visible under the skin over the contour of the sternocleidomastoid muscle, especially when venous return from the head is impeded (for example, during straining or when performing exercises such as a handstand).

The Anterior jugular vein begins in the submental region, runs vertically downward, and drains into the subclavian vein posterior to the Water/144.html">Origin of the sternocleidomastoid muscle. The right and left anterior jugular veins frequently anastomose with each other, forming the jugular venous arch.    

The subclavian vein passes anterior to the anterior scalene muscle, forming an upward-facing arch. It receives several small veins of the neck and scapula and, as a continuation of the axillary vein, drains venous blood from the shoulder girdle and the free upper limb.

The veins of the upper limb are divided into deep and superficial. They possess A large number of well-developed valves and form numerous anastomoses.

The deep veins accompany the arteries and share their names. Each artery is accompanied by two veins. The only exceptions are the digital veins and the axillary vein. The axillary vein is formed by the union of the two brachial veins and runs from the lower border of the pectoralis major muscle to the clavicle, where it becomes the subclavian vein. All deep veins of the upper limb receive numerous tributaries in the form of small veins that drain blood from the areas through which they pass.

The superficial veins of the upper limb include the cephalic and basilic veins (see Fig. 99). They arise from the venous plexuses of the hand and run along the lateral and medial aspects of the arm. The cephalic vein drains into the axillary vein, while the basilic vein drains into the brachial vein. The median cubital vein, which connects the cephalic and basilic veins, is located in the cubital fossa.

In many individuals, the superficial veins of the upper limb dilate significantly during muscular exertion. Small bulges corresponding to the locations of the valves are often visible along their course.

The inferior vena cava drains blood from the lower limbs, the pelvic walls, and partly from the abdomen, as well as from the internal organs located within the abdominal cavity. Blood from the unpaired abdominal organs first drains into the portal vein and passes through the liver.

The inferior vena cava is the largest vein in the human body. It is formed by the confluence of the right and left common iliac veins at the level of the 4th and 5th lumbar vertebrae. It lies to the right of the abdominal aorta and is covered anteriorly by the Peritoneum along almost its entire length. Passing through the caval opening in the central tendon of the diaphragm, the inferior vena cava enters the thoracic cavity and, after traversing the pericardial cavity, opens into the right atrium.

Numerous veins drain into the inferior vena cava, which can be divided into two groups: visceral tributaries (draining the internal organs) and parietal tributaries (draining the walls of the abdominal cavity, pelvis, and the lower limbs).

The parietal veins include the lumbar and phrenic veins.

Four pairs of lumbar veins accompany the corresponding arteries, draining blood from the vertebral column, skin, and Muscles of the Trunk. They anastomose with each other to form two vertical channels—the ascending lumbar veins—located on either side of the vertebral column. The right ascending lumbar vein continues as the azygos vein, while the left continues as the hemiazygos vein. The inferior phrenic vein follows the course of the corresponding artery. Unlike the veins of the limbs, these veins have poorly developed valves. The inferior vena cava itself has no valves.

The visceral tributaries that drain into the inferior vena cava include the testicular (ovarian in females), renal, suprarenal, and hepatic veins.

The testicular vein drains blood from the testis. It forms a dense plexus (the pampiniform plexus) within the spermatic cord. It has a very long course, passing through the inguinal canal and ascending to the level of the 1st and 2nd lumbar vertebrae, where the right testicular vein drains into the inferior vena cava, and the left drains into the left renal vein. In females, the ovarian vein drains blood from the ovary. It also forms a venous plexus located within the broad ligament of the uterus. The valves of these veins are poorly developed.

The renal vein drains blood from the Kidney. It empties into the inferior vena cava at approximately the same level as the aforementioned veins. The renal vein anastomoses with several parietal veins, particularly the lumbar, azygos, and hemiazygos veins.

The right suprarenal vein drains into the inferior vena cava, while the left drains into the left renal vein.

The hepatic veins drain into the inferior vena cava as two or three large trunks at the point where the inferior vena cava closely adheres to the liver. The hepatic veins drain blood from the liver that has entered it via the portal vein and the hepatic artery.

The portal vein (see Fig. 100) drains blood from the abdominal viscera: the spleen, stomach, pancreas, gallbladder, and the small and large intestines. Only from the proximal part of the stomach and the lower rectum does blood drain not into the portal vein, but into the superior and inferior vena cava systems, respectively.

The portal vein is a thick, short venous trunk. Running within the hepatoduodenal ligament, it enters the liver, where it divides into branches. Its terminal branches run between the hepatic lobules as interlobular veins, adjacent to the interlobular arteries. From these veins, blood flows through the intralobular capillaries (sinusoids) into the central veins located at the center of each lobule.

Merging together, the central veins form the hepatic veins. Thus, blood from these abdominal organs passes through a capillary bed twice: first within the organs themselves, where it transitions from arteries to veins, and second within the liver, as it passes from the portal vein system to the inferior vena cava system.

Anastomoses between the portal vein and the caval system (portocaval anastomoses) exist in the retroperitoneal adipose tissue, the pelvic cavity, along the esophagus, and along the round ligament of the liver (see Fig. 100).

The largest tributaries of the portal vein are the superior mesenteric, inferior mesenteric, and splenic veins.

The superior mesenteric vein lies within the mesentery of the small intestine and drains blood from the jejunum, ileum, cecum, ascending colon, and transverse colon, as well as partly from the stomach, duodenum, pancreas, and greater omentum.

The inferior mesenteric vein drains blood from the descending colon, sigmoid colon, and the upper part of the rectum.

The splenic vein drains blood from the spleen and partially from the stomach, pancreas, duodenum, and greater omentum.

The portal Venous system is generally devoid of valves.

The common iliac vein is formed by the union of the internal and external iliac veins at the level of the sacroiliac joint. The left common iliac vein is longer than the right, because THE ORIGIN OF the inferior vena cava lies slightly to the right of the midline. The right common iliac vein lies posterior and slightly lateral to the corresponding artery, whereas the left common iliac vein runs initially medial and then posterior to the common iliac artery. The median sacral vein, which accompanies the corresponding artery, drains into the left common iliac vein.

The internal iliac vein lies posterior to the corresponding artery and drains blood from both the pelvic organs and the pelvic walls. The visceral tributaries of this vein include those from the rectum, genitalia, and urinary bladder. Well-developed venous plexuses are located around the rectal wall, internal genitalia, and urinary bladder. In the rectum, two plexuses are distinguished: one located in the submucosa and the other superficial to the muscular layer. In males, the venous plexuses of the internal genitalia drain blood from the Prostate Gland, Seminal Vesicles, and the proximal Urethra; in females, they drain the uterus, vagina, and external genitalia.

The external iliac vein is the second major tributary of the common iliac vein, serving as its direct upward continuation. The external iliac vein, in turn, is the continuation of the femoral vein, which drains blood from the lower limb. The boundary between the femoral and external iliac veins is defined by the level of the inguinal ligament, beneath which the femoral vein passes through an opening called the vascular lacuna. The external iliac vein receives the inferior epigastric vein, which runs alongside the corresponding artery, and the deep circumflex iliac vein. The former has numerous anastomoses with the superior vena cava system.

The veins of the lower limb follow the same general anatomical pattern as those of the upper limb. They are divided into deep and superficial veins. The deep veins accompany the arteries and share their names. In the foot and leg, they are paired (venae comitantes) for each artery.

The superficial veins of the foot run along the dorsum of the toes, interconnecting at the level of the metatarsophalangeal joints to form the dorsal digital veins of the foot, which drain into a well-developed dorsal venous arch. The dorsum of the foot gives rise to the two major superficial veins of the lower limb: the great and small saphenous veins.

Originating near the great toe, the great saphenous vein ascends along the medial margin of the foot, the medial aspect of the leg, and the thigh, ultimately reaching the saphenous opening (fossa ovalis) of the fascia lata. Curving over the margin of this fossa, it empties into the femoral vein.

The small saphenous vein begins on the lateral side of the foot, courses along the posterior aspect of the leg, and drains into the popliteal vein. The superficial veins form numerous anastomoses with one another as well as with the deep veins. Like all veins of the lower extremity, they feature well-developed valves that direct blood flow from the superficial veins into the deep system. Just inferior to the junction where the great saphenous vein empties into the femoral vein, there is also a valve that prevents the backflow of blood from the femoral vein into the saphenous vein.