Human Anatomy_部分3

580 PA RT FO UR MaintenanceTABLE 21.3 Veins of the Head and Neck (continued)Superiorsagittal sinusConfluence ofsinusesSigmoid sinusTransversesinus(a) Dural venous sinuses, medial view (b) Dural venous sinuses, inferior view(c) Superficial veins of the head and neckGreat cerebral v.Straight sinusInferiorsagittal sinusCorpus callosumSuperior thyroid v.Superiorophthalmic v.Facial v.Internaljugular v.Brachiocephalic v. Axillary v.Subclavian v.Externaljugular v.Vertebral v.Occipital v.Superficialtemporal v.Straight sinusTo internaljugular v.Confluence ofsinusesTransversesinusInternal jugular v.SigmoidsinusCavernoussinusSuperiorophthalmic v.Superficialmiddle cerebral v.Thyroid glandFigure 21.19 Veins of the Head and Neck. (a) Dural venous sinuses seen in a median section of the cerebrum. (b) Dural venous sinuses seen in an inferior view of the cerebrum. (c) Superficial (extracranial) veins of the head and neck. the cerebrum. (c) Superficial (extracranial) sal03709_ch21_563-608.indd 580 06/11/15 10:51 AM CH A P T E R T W E N T Y- O N E The Circulatory System III: Blood Vessels 581TABLE 21.4 Arteries of the ThoraxThe thorax is supplied by several arteries arising directly from the aorta (parts I and II of this table) and from the subclavian and axillary arteries (part III). The thoracic aorta begins distal to the aortic arch and ends at the aortic hiatus (hy-AY-tus), a passage through the diaphragm. Along the way, it sends off numerous small branches to the thoracic viscera and the body wall (fig. 21.20).I. Visceral Branches of the Thoracic AortaThese supply the viscera of the thoracic cavity: 1. Bronchial arteries. Although variable in number and arrangement, there are usually two of these on the left and one on the right. The right bronchial artery usually arises from one of the left bronchial arteries or from a posterior intercostal artery (see part II.1). The bronchial arteries supply the bronchi, bronchioles, and larger blood vessels of the lungs, the visceral pleura, the pericardium, and the esophagus. 2. Esophageal arteries. Four or five unpaired esophageal arteries arise from the anterior surface of the aorta and supply the esophagus. 3. Mediastinal arteries. Many small mediastinal arteries (not illustrated) supply structures of the posterior mediastinum.R. subclavian a.Costocervical trunkThoracoacromial trunkLateral thoracic a.Subscapular a.Internal thoracic a.Thyrocervical trunkR. common carotid a.L. common carotid a.L. subclavian a.Bronchial aa.Posterior intercostal aa.Esophageal aa.Pericardiophrenic a.Vertebral a.Anterior intercostal aa.Subcostal a.(a) Major arteries(b) Blood-flow schematicCostocervical trunkThoracoacromialtrunkLateral thoracic a.Subscapular a.Internal thoracic a.Thyrocervical trunkCommon carotid aa.Brachiocephalic trunkL. subclavian a.Aortic archBronchial aa.Descending aortaPosterior intercostal aa.Esophageal aa.Pericardiophrenic a.Vertebral a.Anteriorintercostal aa.Subcostal a.Figure 21.20 Arteries of the Thorax. sal03709_ch21_563-608.indd 581 06/11/15 10:51 AM TABLE 21.4 Arteries of the Thorax (continued)II. Parietal Branches of the Thoracic AortaThe following branches supply chiefly the muscles, bones, and skin of the chest wall; only the first are illustrated:1. Posterior intercostal arteries. Nine pairs of these arise from the posterior surface of the aorta and course around the posterior side of the rib cage between ribs 3 through 12, then anastomose with the anterior intercostal arteries (see part III.1 in this table). They supply the intercostal, pectoralis, serratus anterior, and some abdominal muscles, as well as the vertebrae, spinal cord, meninges, breasts, skin, and subcutaneous tissue. They are enlarged in lactating women.2. Subcostal arteries. A pair of these arise from the aorta inferior to the twelfth rib. They supply the posterior intercostal tissues, vertebrae, spinal cord, and deep muscles of the back.3. Superior phrenic 11 (FREN-ic) arteries (not illustrated). These arteries, variable in number, arise at the aortic hiatus and supply the superior and posterior regions of the diaphragm.III. Branches of the Subclavian and Axillary ArteriesThe thoracic wall is also supplied by the following arteries, which arise in the shoulder region—the first one from the subclavian artery and the other three from its continuation, the axillary artery:1. The internal thoracic (mammary) artery supplies the breast and anterior thoracic wall and issues the following branches:a. The pericardiophrenic artery supplies the pericardium and diaphragm.b. The anterior intercostal arteries arise from the thoracic artery as it descends alongside the sternum. They travel between the ribs, supply the ribs and intercostal muscles, and anastomose with the posterior intercostal arteries. Each of these sends one branch along the lower margin of the rib above and another branch along the upper margin of the rib below.2. The thoracoacromial 12 (THOR-uh-co-uh-CRO-me-ul) trunk provides branches to the superior shoulder and pectoral regions.3. The lateral thoracic artery supplies the pectoral, serratus anterior, and subscapularis muscles. It also issues branches to the breast and is larger in females than in males.4. The subscapular artery is the largest branch of the axillary artery. It supplies the scapula and the latissimus dorsi, serratus anterior, teres major, deltoid, triceps brachii, and intercostal muscles.TABLE 21.5 Veins of the ThoraxI. Tributaries of the Superior Vena CavaThe most prominent veins of the upper thorax are as follows. They carry blood from the shoulder region to the heart (fig. 21.21).1. The subclavian vein drains the upper limb (see table 21.9). It begins at the lateral margin of the first rib and travels posterior to the clavicle. It receives the external jugular and vertebral veins, then ends where it receives the internal jugular vein.2. The brachiocephalic vein is formed by union of the subclavian and internal jugular veins. The right brachiocephalic is very short, about 2.5 cm, and the left is about 6 cm long. They receive tributaries from the vertebrae, thyroid gland, and upper thoracic wall and breast, then converge to form the next vein. 3. The superior vena cava is formed by the union of the right and left brachiocephalic veins. It travels inferiorly for about 7 cm and empties into the right atrium of the heart. Its main tributary is the azygos vein. It drains all structures superior to the diaphragm except the pulmonary circuit and coronary circulation. It also receives drainage from the abdominal cavity by way of the azygos system, described next.II. The Azygos SystemThe principal venous drainage of the thoracic organs is by way of the azygos (AZ-ih-goss) system (fig. 21.21). The most prominent vein of this system is the azygos 13 vein, which ascends the right side of the posterior thoracic wall and is named for the lack of a mate on the left. It receives the following tributaries, then empties into the superior vena cava at the level of vertebra T4.1. The right ascending lumbar vein drains the right abdominal wall, then penetrates the diaphragm and enters the thoracic cavity. The azygos vein begins where the ascending lumbar vein meets the right subcostal vein beneath rib 12.2. The right posterior intercostal veins drain the intercostal spaces. The first (superior) one empties into the right brachiocephalic vein; intercostals 2 and 3 join to form a right superior intercostal vein before emptying into the azygos; and intercostals 4 through 11 each enter the azygos vein separately. 3. The right esophageal, mediastinal, pericardial, and bronchial veins (not illustrated) drain their respective organs into the azygos.4. The hemiazygos 14 vein ascends the posterior thoracic wall on the left. It begins where the left ascending lumbar vein, having just penetrated the diaphragm, joins the subcostal vein below rib 12. The hemiazygos then receives the lower three posterior intercostal veins, esophageal veins, and mediastinal veins. At the level of vertebra T9, it crosses to the right and empties into the azygos. 5. The accessory hemiazygos vein descends the posterior thoracic wall on the left. It receives drainage from posterior intercostal veins 4 through 8 and sometimes the left bronchial veins. It crosses to the right at the level of vertebra T8 and empties into the azygos vein. The left posterior intercostal veins 1 through 3 are the only ones on this side that do not ultimately drain into the azygos vein. The first one usually drains directly into the left brachiocephalic vein. The second and third unite to form the left superior intercostal vein, which empties into the left brachiocephalic vein.11 phren = diaphragm12 thoraco = chest; acr = tip; om = shoulder13 unpaired; from a = without; zygo = union, mate14 hemi = halfsal03709_ch21_563-608.indd 582 06/11/15 10:51 AM CH A P T E R T W E N T Y- O N E The Circulatory System III: Blood Vessels 583TABLE 21.5 Veins of the Thorax (continued)L. posteriorintercostal vv.R. posteriorintercostal vv.R. superiorintercostal v.Brachiocephalic vv.Azygos v.R. subcostal v.DiaphragmR. lumbar vv.Superior vena cavaInferior vena cavaL. iliolumbar v.Renal vv.Accessory hemiazygos v.L. subcostal v.L. ascending lumbar v. R. ascending lumbar v.R. iliolumbar v.R. common iliac v.(b)(a)L. common iliac v.L. lumbar vv.Hemiazygos v.L. superiorintercostal v.123123445678 91011123234145678 91011Internal jugular v.Subclavian v.Brachiocephalic v.Superior intercostal v.Superior vena cavaAccessory hemiazygos v.Posterior intercostal vv.Hemiazygos v.Rib 12L. ascending lumbar v.Lumbar vv.R. ascending lumbar v.Azygos v.Superior intercostal v.Posterior intercostal v.Subcostal v.T12T8T4T9Figure 21.21 Venous Drainage of the Posterior Wall of the Thorax and Abdomen. (a) The azygos system of the thoracic wall. This system provides venous drainage from the wall and viscera of the thorax, but the visceral tributaries are not illustrated. (b) Blood-flow schematic of thoracic and abdominal drainage. The components above the diaphragm constitute the azygos system. There is a great deal of individual variation in this pattern. the azygos system. There is a great deal of sal03709_ch21_563-608.indd 583 06/11/15 10:51 AM TABLE 21.6 Arteries of the Abdomen and Pelvic RegionAfter passing through the aortic hiatus, the aorta descends through the abdominal cavity and ends at the level of vertebra L4, where it branches into right and left common iliac arteries. The abdominal aorta is retroperitoneal. I. Major Branches of the Abdominal AortaThe abdominal aorta gives off arteries in the order listed here (fig. 21.22). Those indicated in the plural are paired right and left, and those indicated in the singular are solitary median arteries.1. The inferior phrenic arteries supply the inferior surface of the diaphragm. They may arise from the aorta, celiac trunk, or renal artery. Each issues two or three small superior suprarenal arteries to the ipsilateral adrenal (suprarenal) gland.2. The celiac 15 (SEE-lee-ac) trunk supplies the upper abdominal viscera (see part II of this table).3. The superior mesenteric artery supplies the intestines (see part III). 4. The middle suprarenal arteries arise laterally from the aorta, usually at the same level as the superior mesenteric artery; they supply the adrenal glands.5. The renal arteries supply the kidneys and issue a small inferior suprarenal artery to each adrenal gland.6. The gonadal arteries (ovarian arteries in the female and testicular arteries in the male) are long, slender arteries that arise from the midabdominal aorta and descend along the posterior body wall to the female pelvic cavity or male scrotum. The gonads begin their embryonic development near the kidneys, and the gonadal arteries are then quite short. As the gonads descend to the pelvic cavity, these arteries grow and acquire their peculiar length and course.7. The inferior mesenteric artery supplies the distal end of the large intestine (see part III).8. The lumbar arteries arise from the lower aorta in four pairs. They supply the posterior abdominal wall (muscles, joints, and skin) and the spinal cord and other tissues in the vertebral canal.9. The median sacral artery, a tiny medial artery at the inferior end of the aorta, supplies the sacrum and coccyx.10. The common iliac arteries arise as the aorta forks at its inferior end. They are further traced in part IV of this table.II. Branches of the Celiac TrunkThe celiac circulation to the upper abdominal viscera is perhaps the most complex route off the abdominal aorta. Because it has numerous anastomoses, the bloodstream does not follow a simple linear path but divides and rejoins itself at several points (fig. 21.23). As you study the following description, locate these branches in the figure and identify the points of anastomosis. The short, stubby celiac trunk, barely more than 1 cm long, is a median branch of the aorta just below the diaphragm. It immediately gives rise to three branches—the common hepatic, left gastric, and splenic arteries.1. The common hepatic artery passes to the right and issues two main branches—the gastroduodenal artery and the hepatic artery proper.a. The gastroduodenal artery gives off the right gastro-omental (gastroepiploic 16 ) artery to the stomach. It then continues as the superior pancreaticoduodenal (PAN-cree-AT-ih-co-dew-ODD-eh-nul) artery, which splits into two branches that pass around the anterior and posterior sides of the head of the pancreas. These anastomose with the two branches of the inferior pancreaticoduodenal artery, discussed in part III.1.b. The hepatic artery proper ascends toward the liver. It gives off the right gastric artery, then branches into right and left hepatic arteries. The right hepatic artery issues a cystic artery to the gallbladder, then the two hepatic arteries enter the liver from below. 2. The left gastric artery supplies the stomach and lower esophagus, arcs around the lesser curvature (superomedial margin) of the stomach, and anastomoses with the right gastric artery (fig. 21.23b). Thus, the right and left gastric arteries approach from opposite directions and supply this margin of the stomach. The left gastric also has branches to the lower esophagus, and the right gastric also supplies the duodenum.3. The splenic artery supplies blood to the spleen, but gives off the following branches on the way there:a. Several small pancreatic arteries supply the pancreas.b. The left gastro-omental (gastroepiploic) artery arcs around the greater curvature (inferolateral margin) of the stomach and anastomoses with the right gastro-omental artery. These two arteries stand off about 1 cm from the stomach itself and travel through the superior margin of the greater omentum, a fatty membrane suspended from the greater curvature (see figs. A.4, p. 334, and 24.3, p. 657). They furnish blood to both the stomach and omentum.c. The short gastric arteries supply the upper portion (fundus) of the stomach.Aortic hiatusInferior phrenic a.Celiac trunkSuperiorMiddleInferiorSuperior mesenteric a.Renal a.Gonadal a.Inferior mesenteric a.Lumbar aa.Common iliac a.Median sacral a.Suprarenalaa. Internal iliac a.Figure 21.22 The Abdominal Aorta and Its Major Branches. 15 celi = belly, abdomen16 gastro = stomach; epi = upon, above; ploic = pertaining to the greater omentumsal03709_ch21_563-608.indd 584 06/11/15 10:51 AM TABLE 21.6 Arteries of the Abdomen and Pelvic Region (continued)R. gastro-omental a.L. gastro-omental a.Splenic a.(a) Branches of the celiac trunkInferiorpancreaticoduodenal a.Superiorpancreaticoduodenal a.DuodenumGastroduodenal a.R. gastric a. L. gastric a.Hepatic a. properHepatic aa.Cystic a.LiverGallbladderSpleenAortaSuperior mesenteric a.PancreasPancreatic aa.Common hepatic a.Shortgastric aa.Celiac trunk(b) Celiac circulation to the stomachGastroduodenal a.Left gastric a.Shortgastric aa.Splenic a.Left gastro-omental a.Right gastro-omental a.Right gastric a.LiverIntestinesPancreasSpleenSuperiorpancreaticoduodenal a.R. gastro-omental a.Gastroduodenal a.R. gastric a.Common hepatic a.Hepatic a. properAortaStomachCeliac trunkSplenic a.Inferior pancreaticoduodenal a.Shortgastric aa.L. gastro-omental a.Superior mesenteric a.L. gastric a.(c) Blood-flow schematicHepatic aa.Cystic a.Figure 21.23 Branches of the Celiac Trunk. (a) Anatomy of the celiac system with the stomach removed to expose the more posterior arteries. (b) Arterial supply to the stomach. (c) Blood-flow schematic of the celiac system. sal03709_ch21_563-608.indd 585 06/11/15 10:51 AM 586 PA RT FO UR MaintenanceTABLE 21.6 Arteries of the Abdomen and Pelvic Region (continued)III. Mesenteric CirculationThe mesentery is a translucent sheet that suspends the intestines and other abdominal viscera from the posterior body wall (see figs. 1.15, p. 19, and 24.3, p. 657). It contains numerous arteries, veins, and lymphatic vessels that supply and drain the intestines. The arterial supply arises from the superior and inferior mesenteric arteries; numerous anastomoses between these ensure adequate collateral circulation to the intestines even if one route is temporarily obstructed. The superior mesenteric artery (fig. 21.24a) is the most significant intestinal blood supply, serving nearly all of the small intestine and the proximal half of the large intestine. It arises medially from the upper abdominal aorta and gives off the following branches:1. The inferior pancreaticoduodenal artery, already mentioned, branches to pass around the anterior and superior sides of the pancreas and anastomose with the two branches of the superior pancreaticoduodenal artery.2. Twelve to 15 jejunal and ileal arteries form a fanlike array that supplies nearly all of the small intestine (portions called the jejunum and ileum).3. The ileocolic (ILL-ee-oh-CO-lic) artery supplies the ileum, appendix, and parts of the large intestine (cecum and ascending colon).4. The right colic artery also supplies the ascending colon.5. The middle colic artery supplies most of the transverse colon.The inferior mesenteric artery arises from the lower abdominal aorta and serves the distal part of the large intestine (fig. 21.24b):1. The left colic artery supplies the transverse and descending colon.2. The sigmoid arteries supply the descending and sigmoid colon.3. The superior rectal artery supplies the rectum.Middlecolic a.R. colic a.Ileocolic a.Ascending colonCecumIleumIleal aa.Jejunal aa.JejunumTransverse colonSuperior mesenteric a.AppendixInferiorpancreaticoduodenal a.(a) Distribution of superior mesenteric arteryAortaLeft colic a.AortaInferior mesenteric a.RectumSigmoid colonTransverse colonSuperior rectal a.Descending colonSigmoid aa.(b) Distribution of inferior mesenteric arteryFigure 21.24 The Mesenteric Arteries. sal03709_ch21_563-608.indd 586 06/11/15 10:51 AM CH A P T E R T W E N T Y- O N E The Circulatory System III: Blood Vessels 58717 vesic = bladder18 pudend = literally “shameful parts”; the external genitalsTABLE 21.6 Arteries of the Abdomen and Pelvic Region (continued)IV. Arteries of the Pelvic RegionThe two common iliac arteries arise by branching of the aorta, descend for another 5 cm, and then, at the level of the sacroiliac joint, each divides into an external and internal iliac artery. The external iliac supplies mainly the lower limb (see table 21.10). The internal iliac artery supplies mainly the pelvic wall and viscera. Its branches are shown only in schematic form in figure 21.30.Shortly after its origin, the internal iliac divides into anterior and posterior trunks. The anterior trunk produces the following branches: 1. The superior vesical 17 artery supplies the urinary bladder and distal end of the ureter. It arises indirectly from the anterior trunk by way of a short umbilical artery, a remnant of the artery that supplies the fetal umbilical cord. The rest of the umbilical artery becomes a closed fibrous cord after birth. 2. In men, the inferior vesical artery supplies the bladder, ureter, prostate gland, and seminal vesicle. In women, the corresponding vessel is the vaginal artery, which supplies the vagina and part of the bladder and rectum. 3. The middle rectal artery supplies the rectum. 4. The obturator artery exits the pelvic cavity through the obturator foramen and supplies the adductor muscles of the medial thigh. 5. The internal pudendal 18 (pyu-DEN-dul) artery serves the perineum and erectile tissues of the penis and clitoris; it supplies the blood for vascular engorgement during sexual arousal. 6. In women, the uterine artery is the main blood supply to the uterus and supplies some blood to the vagina. It enlarges substantially in pregnancy. It passes up the uterine margin, then turns laterally at the uterine tube and anastomoses with the ovarian artery, thus supplying blood to the ovary as well (see part I.6 of table 21.6, and fig. 26.18, p. 722). 7. The inferior gluteal artery supplies the gluteal muscles and hip joint.The posterior trunk produces the following branches: 1. The iliolumbar artery supplies the lumbar body wall and pelvic bones. 2. The lateral sacral arteries lead to tissues of the sacral canal, skin, and muscles posterior to the sacrum. There are usually two of these, superior and inferior. 3. The superior gluteal artery supplies the skin and muscles of the gluteal region and the muscle and bone tissues of the pelvic wall.sal03709_ch21_563-608.indd 587 06/11/15 10:51 AM TABLE 21.7 Veins of the Abdomen and Pelvic RegionI. Tributaries of the Inferior Vena CavaThe inferior vena cava (IVC) is the body’s largest blood vessel, having a diameter of about 3.5 cm. It forms by the union of the right and left common iliac veins at the level of vertebra L5 and drains many of the abdominal viscera as it ascends the posterior body wall. It is retroperitoneal and lies immediately to the right of the aorta. The IVC picks up blood from numerous tributaries in the following ascending order (fig. 21.25):1. The internal iliac veins drain the gluteal muscles; the medial aspect of the thigh, the urinary bladder, rectum, prostate, and ductus deferens of the male; and the uterus and vagina of the female. They unite with the external iliac veins, which drain the lower limb and are described in table 21.11. Their union forms the common iliac veins, which then converge to form the IVC. 2. Four pairs of lumbar veins empty into the IVC, as well as into the ascending lumbar veins described in part II.3. The gonadal veins (ovarian veins in the female and testicular veins in the male) drain the gonads. Like the gonadal arteries, and for the same reason (table 21.6, part I.6), these are long slender vessels that end far from their origins. The left gonadal vein empties into the left renal vein, whereas the right gonadal vein empties directly into the IVC.4. The renal veins drain the kidneys into the IVC. The left renal vein also receives blood from the left gonadal and left suprarenal veins. It is up to three times as long as the right renal vein, since the IVC lies to the right of the median plane of the body.5. The suprarenal veins drain the adrenal (suprarenal) glands. The right suprarenal empties directly into the IVC, and the left suprarenal empties into the left renal vein.6. The inferior phrenic veins drain the inferior aspect of the diaphragm.7. The hepatic veins drain the liver, extending a short distance from its superior surface to the IVC.After receiving these inputs, the IVC penetrates the diaphragm and enters the right atrium of the heart from below. It does not receive any thoracic drainage.II. Veins of the Abdominal WallA pair of ascending lumbar veins receives blood from the common iliac veins below and the aforementioned lumbar veins of the posterior body wall (see fig. 21.21b). The ascending lumbar veins give off anastomoses with the inferior vena cava beside them as they ascend to the diaphragm. The left ascending lumbar vein passes through the diaphragm via the aortic hiatus and continues as the hemiazygos vein above. The right ascending lumbar vein passes through the diaphragm to the right of the vertebral column and continues as the azygos vein. The further paths of the azygos and hemiazygos veins are described in table 21.5.Inferior phrenic v.L. suprarenal v.R. suprarenal v.Hepatic vv.L. ascending lumbar v.R. renal v.L. renal v.L. gonadal v. R. gonadal v.Lumbar vv. 1–4Common iliac v.Internal iliac v.External iliac v.R. ascending lumbar v.Lumbar v.1Lumbar vv. 2–4Median sacral v.Iliolumbar v.DiaphragmInferior vena cavaFigure 21.25 The Inferior Vena Cava and Its Tributaries. Compare the blood-flow schematic in figure 21.21b.• Why do the veins that drain the ovaries and testes terminate so far away from the gonads? 588sal03709_ch21_563-608.indd 588 06/11/15 10:51 AM CH A P T E R T W E N T Y- O N E The Circulatory System III: Blood Vessels 589TABLE 21.7 Veins of the Abdomen and Pelvic Region (continued) III. The Hepatic Portal SystemThe hepatic portal system receives all of the blood draining from the abdominal digestive tract, as well as from the pancreas, gallbladder, and spleen (fig. 21.26). It is called a portal system because it connects capillaries of the intestines and other digestive organs to modified capillaries (hepatic sinusoids) of the liver; thus, the blood passes through two capillary beds in series before it returns to the heart. Intestinal blood is richly laden with nutrients for a few hours following a meal. The hepatic portal system gives the liver first claim to these nutrients before the blood is distributed to the rest of the body. It also allows the blood to be cleansed of bacteria and toxins picked up from the intestines, an important function of the liver. Its principal veins are as follows: 1. The inferior mesenteric vein receives blood from the rectum and distal part of the colon. It converges in a fanlike array in the mesentery and empties into the splenic vein. 2. The superior mesenteric vein receives blood from the entire small intestine, ascending colon, transverse colon, and stomach. It, too, exhibits a fanlike arrangement in the mesentery and then joins the splenic vein to form the hepatic portal vein. 3. The splenic vein drains the spleen and travels across the abdominal cavity toward the liver. Along the way, it picks up pancreatic veins from the pancreas, then the inferior mesenteric vein, then ends where it meets the superior mesenteric vein. 4. The hepatic portal vein is the continuation beyond the convergence of the splenic and superior mesenteric veins. It travels about 8 cm upward and to the right, receives the cystic vein from the gallbladder, then enters the inferior surface of the liver. In the liver, it ultimately leads to the innumerable microscopic hepatic sinusoids. Blood from the sinusoids empties into the hepatic veins described earlier, and they empty into the IVC. Circulation within the liver is described in more detail in chapter 24 (p. 676). 5. The left and right gastric veins form an arc along the lesser curvature of the stomach and empty into the hepatic portal vein.Hepatic vv.LiverGallbladderHepatic portal v.Cystic v.IleumRectum(a) Tributaries of the hepatic portal systemSpleenInferior vena cavaR. gastro-omental v.Inferior mesenteric v.Superior mesenteric v.ColonSplenic v.Gastric vv. (b) Blood-flow schematicSuperiormesenteric v.R. gastro-omental v.Hepaticportal v.Cystic v.LiverSplenic v.Inferiormesenteric v.HepaticsinusoidsHepatic v.Inferior venacavaPancreasL. gastric v.R. gastric v.L. gastro-omental v.SpleenPancreatic vv.GallbladderFigure 21.26 The Hepatic Portal System. sal03709_ch21_563-608.indd 589 06/11/15 10:51 AM 590 PA RT FO UR MaintenanceBefore You Go OnAnswer the following questions to test your understanding of the preceding section:9. Concisely contrast the destinations of the external and internal carotid arteries.10. Briefly state the organs or parts of organs that are supplied with blood by (a) the cerebral arterial circle, (b) the celiac trunk, (c) the superior mesenteric artery, and (d) the internal iliac artery.11. If you were dissecting a cadaver, where would you look for the internal and external jugular veins? What muscle would help you distinguish one from the other?12. Trace a blood cell from the left lumbar body wall to the superior vena cava, naming the vessels through which it would travel.13. Explain the functional importance of having a hepatic portal system connect capillaries of the intestines to capillaries of the liver.Systemic Vessels of the Appendicular RegionExpected Learning OutcomesWhen you have completed this section, you should be able toa. identify the principal systemic arteries and veins of the limbs; andb. trace the flow of blood from the heart to any region of the upper or lower limb and back to the heart.The principal vessels of the appendicular region are detailed in tables 21.8 through 21.11. While the appendicular arteries are usually deep and well protected, the veins occur in both deep and superficial groups; you may be able to see several of the superficial ones in your arms and hands. Deep veins run parallel to the arteries and often have similar names (femoral artery and femoral vein, for example). In several cases, the deep veins occur in pairs flanking the corresponding artery (such as the two radial veins traveling alongside the radial artery).These blood vessels will be described in an order correspond-ing to the direction of blood flow. Thus, we will begin with the arteries in the shoulder and pelvic regions and progress to the hands and feet, whereas we will trace the veins beginning in the hands and feet and progressing toward the heart. Venous pathways have more anastomoses than arterial path-ways, so the route of flow is often not as clear. If all the anastomoses were illustrated, many of these venous pathways would look more like confusing networks than a clear route back to the heart. Therefore, most anastomoses—especially the highly variable and unnamed ones—are omitted from the figures to allow you to focus on the more general course of blood flow. The blood-flow sche-matics in several figures will also help to clarify these routes.21.4TABLE 21.8 Arteries of the Upper LimbThe upper limb is supplied by a prominent artery that changes name along its course from subclavian to axillary to brachial, then issues branches to the arm, forearm, and hand (fig. 21.27).I. The Shoulder and Arm (Brachium) 1. The brachiocephalic trunk arises from the aortic arch and branches into the right common carotid artery and left subclavian artery; the right subclavian artery arises directly from the aortic arch. Each subclavian arches over the respective lung, rising as high as the base of the neck slightly superior to the clavicle. It then passes posterior to the clavicle, downward over the first rib, and ends in name only at the rib’s lateral margin. In the shoulder, it gives off several small branches to the thoracic wall and viscera, described in table 21.4. 2. As the artery continues past the first rib, it is named the axillary artery. It continues through the axillary region, gives off small thoracic branches (see table 21.4), and ends, again in name only, at the neck of the humerus. Here, it gives off a pair of circumflex humeral arteries, which encircle the humerus, anastomose with each other laterally, and supply blood to the shoulder joint and deltoid muscle. Beyond this loop, the vessel is called the brachial artery. 3. The brachial (BRAY-kee-ul) artery continues down the medial and anterior sides of the humerus and ends just distal to the elbow, supplying the anterior flexor muscles of the brachium along the way. This artery is the most common site of blood pressure measurement, using an inflatable cuff that encircles the arm and compresses the artery. 4. The deep brachial artery arises from the proximal end of the brachial and supplies the humerus and triceps brachii muscle. About midway down the arm, it continues as the radial collateral artery. 5. The radial collateral artery descends in the lateral side of the arm and empties into the radial artery slightly distal to the elbow. 6. The superior ulnar collateral artery arises about midway along the brachial artery and descends in the medial side of the arm. It empties into the ulnar artery slightly distal to the elbow. II. The Forearm, Wrist, and HandJust distal to the elbow, the brachial artery forks into the radial and ulnar arteries. 1. The radial artery descends the forearm laterally, alongside the radius, nourishing the lateral forearm muscles. The most common place to take a pu...