Datasets:

MedRAG
/

textbooks

Dataset card Viewer Files Files and versions Community

Split (1)

train · 126k rows

id stringlengths 14 28	title stringclasses 18 values	content stringlengths 2 999	contents stringlengths 19 1.02k
Anatomy_Gray_700	Anatomy_Gray	The gallbladder is a pear-shaped sac lying on the visceral surface of the right lobe of the liver in a fossa between the right and quadrate lobes (Fig. 4.104). It has: a rounded end (fundus of the gallbladder), which may project from the inferior border of the liver; a major part in the fossa (body of the gallbladder), which may be against the transverse colon and the superior part of the duodenum; and a narrow part (neck of the gallbladder) with mucosal folds forming the spiral fold. The arterial supply to the gallbladder (Fig. 4.106) is the cystic artery from the right hepatic artery (a branch of the hepatic artery proper). The gallbladder receives, concentrates, and stores bile from the liver. The pancreas lies mostly posterior to the stomach (Figs. 4.107 and 4.108). It extends across the posterior abdominal wall from the duodenum, on the right, to the spleen, on the left.	Anatomy_Gray. The gallbladder is a pear-shaped sac lying on the visceral surface of the right lobe of the liver in a fossa between the right and quadrate lobes (Fig. 4.104). It has: a rounded end (fundus of the gallbladder), which may project from the inferior border of the liver; a major part in the fossa (body of the gallbladder), which may be against the transverse colon and the superior part of the duodenum; and a narrow part (neck of the gallbladder) with mucosal folds forming the spiral fold. The arterial supply to the gallbladder (Fig. 4.106) is the cystic artery from the right hepatic artery (a branch of the hepatic artery proper). The gallbladder receives, concentrates, and stores bile from the liver. The pancreas lies mostly posterior to the stomach (Figs. 4.107 and 4.108). It extends across the posterior abdominal wall from the duodenum, on the right, to the spleen, on the left.
Anatomy_Gray_701	Anatomy_Gray	The pancreas lies mostly posterior to the stomach (Figs. 4.107 and 4.108). It extends across the posterior abdominal wall from the duodenum, on the right, to the spleen, on the left. The pancreas is (secondarily) retroperitoneal except for a small part of its tail and consists of a head, uncinate process, neck, body, and tail. The head of the pancreas lies within the C-shaped concavity of the duodenum. Projecting from the lower part of the head is the uncinate process, which passes posterior to the superior mesenteric vessels. The neck of the pancreas is anterior to the superior mesenteric vessels. Posterior to the neck of the pancreas, the superior mesenteric and splenic veins join to form the portal vein. The body of the pancreas is elongate and extends from the neck to the tail of the pancreas. The tail of the pancreas passes between layers of the splenorenal ligament.	Anatomy_Gray. The pancreas lies mostly posterior to the stomach (Figs. 4.107 and 4.108). It extends across the posterior abdominal wall from the duodenum, on the right, to the spleen, on the left. The pancreas is (secondarily) retroperitoneal except for a small part of its tail and consists of a head, uncinate process, neck, body, and tail. The head of the pancreas lies within the C-shaped concavity of the duodenum. Projecting from the lower part of the head is the uncinate process, which passes posterior to the superior mesenteric vessels. The neck of the pancreas is anterior to the superior mesenteric vessels. Posterior to the neck of the pancreas, the superior mesenteric and splenic veins join to form the portal vein. The body of the pancreas is elongate and extends from the neck to the tail of the pancreas. The tail of the pancreas passes between layers of the splenorenal ligament.
Anatomy_Gray_702	Anatomy_Gray	The body of the pancreas is elongate and extends from the neck to the tail of the pancreas. The tail of the pancreas passes between layers of the splenorenal ligament. The pancreatic duct begins in the tail of the pancreas (Fig. 4.109). It passes to the right through the body of the pancreas and, after entering the head of the pancreas, turns inferiorly. In the lower part of the head of the pancreas, the pancreatic duct joins the bile duct. The joining of these two structures forms the hepatopancreatic ampulla (ampulla of Vater), which enters the descending (second) part of the duodenum at the major duodenal papilla. Surrounding the ampulla is the sphincter of ampulla (sphincter of Oddi), which is a collection of smooth muscles. The accessory pancreatic duct empties into the duodenum just above the major duodenal papilla at the minor duodenal papilla (Fig. 4.109). If the accessory duct is followed from the minor papilla into the head of the pancreas, a branch point is discovered:	Anatomy_Gray. The body of the pancreas is elongate and extends from the neck to the tail of the pancreas. The tail of the pancreas passes between layers of the splenorenal ligament. The pancreatic duct begins in the tail of the pancreas (Fig. 4.109). It passes to the right through the body of the pancreas and, after entering the head of the pancreas, turns inferiorly. In the lower part of the head of the pancreas, the pancreatic duct joins the bile duct. The joining of these two structures forms the hepatopancreatic ampulla (ampulla of Vater), which enters the descending (second) part of the duodenum at the major duodenal papilla. Surrounding the ampulla is the sphincter of ampulla (sphincter of Oddi), which is a collection of smooth muscles. The accessory pancreatic duct empties into the duodenum just above the major duodenal papilla at the minor duodenal papilla (Fig. 4.109). If the accessory duct is followed from the minor papilla into the head of the pancreas, a branch point is discovered:
Anatomy_Gray_703	Anatomy_Gray	One branch continues to the left, through the head of the pancreas, and may connect with the pancreatic duct at the point where it turns inferiorly. A second branch descends into the lower part of the head of the pancreas, anterior to the pancreatic duct, and ends in the uncinate process. The main and accessory pancreatic ducts usually communicate with each other. The presence of these two ducts reflects the embryological origin of the pancreas from dorsal and ventral buds from the foregut.	Anatomy_Gray. One branch continues to the left, through the head of the pancreas, and may connect with the pancreatic duct at the point where it turns inferiorly. A second branch descends into the lower part of the head of the pancreas, anterior to the pancreatic duct, and ends in the uncinate process. The main and accessory pancreatic ducts usually communicate with each other. The presence of these two ducts reflects the embryological origin of the pancreas from dorsal and ventral buds from the foregut.
Anatomy_Gray_704	Anatomy_Gray	The arterial supply to the pancreas (Fig. 4.110) includes the: gastroduodenal artery from the common hepatic artery (a branch of the celiac trunk), anterior superior pancreaticoduodenal artery from the gastroduodenal artery, posterior superior pancreaticoduodenal artery from the gastroduodenal artery, dorsal pancreatic artery from the inferior pancreatic artery (a branch of the splenic artery), great pancreatic artery from the inferior pancreatic artery (a branch of the splenic artery), anterior inferior pancreaticoduodenal artery from the inferior pancreaticoduodenal artery (a branch of the superior mesenteric artery), and posterior inferior pancreaticoduodenal artery from the inferior pancreaticoduodenal artery (a branch of the superior mesenteric artery).	Anatomy_Gray. The arterial supply to the pancreas (Fig. 4.110) includes the: gastroduodenal artery from the common hepatic artery (a branch of the celiac trunk), anterior superior pancreaticoduodenal artery from the gastroduodenal artery, posterior superior pancreaticoduodenal artery from the gastroduodenal artery, dorsal pancreatic artery from the inferior pancreatic artery (a branch of the splenic artery), great pancreatic artery from the inferior pancreatic artery (a branch of the splenic artery), anterior inferior pancreaticoduodenal artery from the inferior pancreaticoduodenal artery (a branch of the superior mesenteric artery), and posterior inferior pancreaticoduodenal artery from the inferior pancreaticoduodenal artery (a branch of the superior mesenteric artery).
Anatomy_Gray_705	Anatomy_Gray	The duct system for the passage of bile extends from the liver, connects with the gallbladder, and empties into the descending part of the duodenum (Fig. 4.111). The coalescence of ducts begins in the liver parenchyma and continues until the right and left hepatic ducts are formed. These drain the respective lobes of the liver. The two hepatic ducts combine to form the common hepatic duct, which runs near the liver, with the hepatic artery proper and portal vein in the free margin of the lesser omentum. As the common hepatic duct continues to descend, it is joined by the cystic duct from the gallbladder. This completes the formation of the bile duct. At this point, the bile duct lies to the right of the hepatic artery proper and usually to the right of, and anterior to, the portal vein in the free margin of the lesser omentum. The omental foramen is posterior to these structures at this point.	Anatomy_Gray. The duct system for the passage of bile extends from the liver, connects with the gallbladder, and empties into the descending part of the duodenum (Fig. 4.111). The coalescence of ducts begins in the liver parenchyma and continues until the right and left hepatic ducts are formed. These drain the respective lobes of the liver. The two hepatic ducts combine to form the common hepatic duct, which runs near the liver, with the hepatic artery proper and portal vein in the free margin of the lesser omentum. As the common hepatic duct continues to descend, it is joined by the cystic duct from the gallbladder. This completes the formation of the bile duct. At this point, the bile duct lies to the right of the hepatic artery proper and usually to the right of, and anterior to, the portal vein in the free margin of the lesser omentum. The omental foramen is posterior to these structures at this point.
Anatomy_Gray_706	Anatomy_Gray	The omental foramen is posterior to these structures at this point. The bile duct continues to descend, passing posteriorly to the superior part of the duodenum before joining with the pancreatic duct to enter the descending part of the duodenum at the major duodenal papilla (Fig. 4.111). The spleen develops as part of the vascular system in the part of the dorsal mesentery that suspends the developing stomach from the body wall. In the adult, the spleen lies against the diaphragm, in the area of rib IX to rib X (Fig. 4.112). It is therefore in the left upper quadrant, or left hypochondrium, of the abdomen. The spleen is connected to the: greater curvature of the stomach by the gastrosplenic ligament, which contains the short gastric and gastro-omental vessels; and left kidney by the splenorenal ligament (Fig. 4.113), which contains the splenic vessels. Both these ligaments are parts of the greater omentum.	Anatomy_Gray. The omental foramen is posterior to these structures at this point. The bile duct continues to descend, passing posteriorly to the superior part of the duodenum before joining with the pancreatic duct to enter the descending part of the duodenum at the major duodenal papilla (Fig. 4.111). The spleen develops as part of the vascular system in the part of the dorsal mesentery that suspends the developing stomach from the body wall. In the adult, the spleen lies against the diaphragm, in the area of rib IX to rib X (Fig. 4.112). It is therefore in the left upper quadrant, or left hypochondrium, of the abdomen. The spleen is connected to the: greater curvature of the stomach by the gastrosplenic ligament, which contains the short gastric and gastro-omental vessels; and left kidney by the splenorenal ligament (Fig. 4.113), which contains the splenic vessels. Both these ligaments are parts of the greater omentum.
Anatomy_Gray_707	Anatomy_Gray	Both these ligaments are parts of the greater omentum. The spleen is surrounded by visceral peritoneum except in the area of the hilum on the medial surface of the spleen (Fig. 4.114). The splenic hilum is the entry point for the splenic vessels, and occasionally the tail of the pancreas reaches this area. The arterial supply to the spleen (Fig. 4.115) is the splenic artery from the celiac trunk. The abdominal aorta begins at the aortic hiatus of the diaphragm, anterior to the lower border of vertebra TXII (Fig. 4.121). It descends through the abdomen, anterior to the vertebral bodies, and by the time it ends at the level of vertebra LIV it is slightly to the left of midline. The terminal branches of the abdominal aorta are the two common iliac arteries. Anterior branches of the abdominal aorta The abdominal aorta has anterior, lateral, and posterior branches as it passes through the abdominal cavity.	Anatomy_Gray. Both these ligaments are parts of the greater omentum. The spleen is surrounded by visceral peritoneum except in the area of the hilum on the medial surface of the spleen (Fig. 4.114). The splenic hilum is the entry point for the splenic vessels, and occasionally the tail of the pancreas reaches this area. The arterial supply to the spleen (Fig. 4.115) is the splenic artery from the celiac trunk. The abdominal aorta begins at the aortic hiatus of the diaphragm, anterior to the lower border of vertebra TXII (Fig. 4.121). It descends through the abdomen, anterior to the vertebral bodies, and by the time it ends at the level of vertebra LIV it is slightly to the left of midline. The terminal branches of the abdominal aorta are the two common iliac arteries. Anterior branches of the abdominal aorta The abdominal aorta has anterior, lateral, and posterior branches as it passes through the abdominal cavity.
Anatomy_Gray_708	Anatomy_Gray	Anterior branches of the abdominal aorta The abdominal aorta has anterior, lateral, and posterior branches as it passes through the abdominal cavity. The three anterior branches supply the gastrointestinal viscera: the celiac trunk and the superior mesenteric and inferior mesenteric arteries (Fig. 4.121). The primitive gut tube can be divided into foregut, midgut, and hindgut regions. The boundaries of these regions are directly related to the areas of distribution of the three anterior branches of the abdominal aorta (Fig. 4.122). The foregut begins with the abdominal esophagus and ends just inferior to the major duodenal papilla, midway along the descending part of the duodenum. It includes the abdominal esophagus, stomach, duodenum (superior to the major papilla), liver, pancreas, and gallbladder. The spleen also develops in relation to the foregut region. The foregut is supplied by the celiac trunk.	Anatomy_Gray. Anterior branches of the abdominal aorta The abdominal aorta has anterior, lateral, and posterior branches as it passes through the abdominal cavity. The three anterior branches supply the gastrointestinal viscera: the celiac trunk and the superior mesenteric and inferior mesenteric arteries (Fig. 4.121). The primitive gut tube can be divided into foregut, midgut, and hindgut regions. The boundaries of these regions are directly related to the areas of distribution of the three anterior branches of the abdominal aorta (Fig. 4.122). The foregut begins with the abdominal esophagus and ends just inferior to the major duodenal papilla, midway along the descending part of the duodenum. It includes the abdominal esophagus, stomach, duodenum (superior to the major papilla), liver, pancreas, and gallbladder. The spleen also develops in relation to the foregut region. The foregut is supplied by the celiac trunk.
Anatomy_Gray_709	Anatomy_Gray	The midgut begins just inferior to the major duodenal papilla, in the descending part of the duodenum, and ends at the junction between the proximal two-thirds and distal one-third of the transverse colon. It includes the duodenum (inferior to the major duodenal papilla), jejunum, ileum, cecum, appendix, ascending colon, and right two-thirds of the transverse colon. The midgut is supplied by the superior mesenteric artery (Fig. 4.122). The hindgut begins just before the left colic flexure (the junction between the proximal two-thirds and distal one-third of the transverse colon) and ends midway through the anal canal. It includes the left one-third of the transverse colon, descending colon, sigmoid colon, rectum, and upper part of the anal canal. The hindgut is supplied by the inferior mesenteric artery (Fig. 4.122).	Anatomy_Gray. The midgut begins just inferior to the major duodenal papilla, in the descending part of the duodenum, and ends at the junction between the proximal two-thirds and distal one-third of the transverse colon. It includes the duodenum (inferior to the major duodenal papilla), jejunum, ileum, cecum, appendix, ascending colon, and right two-thirds of the transverse colon. The midgut is supplied by the superior mesenteric artery (Fig. 4.122). The hindgut begins just before the left colic flexure (the junction between the proximal two-thirds and distal one-third of the transverse colon) and ends midway through the anal canal. It includes the left one-third of the transverse colon, descending colon, sigmoid colon, rectum, and upper part of the anal canal. The hindgut is supplied by the inferior mesenteric artery (Fig. 4.122).
Anatomy_Gray_710	Anatomy_Gray	The celiac trunk is the anterior branch of the abdominal aorta supplying the foregut. It arises from the abdominal aorta immediately below the aortic hiatus of the diaphragm (Fig. 4.123), anterior to the upper part of vertebra LI. It immediately divides into the left gastric, splenic, and common hepatic arteries. The left gastric artery is the smallest branch of the celiac trunk. It ascends to the cardioesophageal junction and sends esophageal branches upward to the abdominal part of the esophagus (Fig. 4.123). Some of these branches continue through the esophageal hiatus of the diaphragm and anastomose with esophageal branches from the thoracic aorta. The left gastric artery itself turns to the right and descends along the lesser curvature of the stomach in the lesser omentum. It supplies both surfaces of the stomach in this area and anastomoses with the right gastric artery.	Anatomy_Gray. The celiac trunk is the anterior branch of the abdominal aorta supplying the foregut. It arises from the abdominal aorta immediately below the aortic hiatus of the diaphragm (Fig. 4.123), anterior to the upper part of vertebra LI. It immediately divides into the left gastric, splenic, and common hepatic arteries. The left gastric artery is the smallest branch of the celiac trunk. It ascends to the cardioesophageal junction and sends esophageal branches upward to the abdominal part of the esophagus (Fig. 4.123). Some of these branches continue through the esophageal hiatus of the diaphragm and anastomose with esophageal branches from the thoracic aorta. The left gastric artery itself turns to the right and descends along the lesser curvature of the stomach in the lesser omentum. It supplies both surfaces of the stomach in this area and anastomoses with the right gastric artery.
Anatomy_Gray_711	Anatomy_Gray	The splenic artery, the largest branch of the celiac trunk, takes a tortuous course to the left along the superior border of the pancreas (Fig. 4.123). It travels in the splenorenal ligament and divides into numerous branches, which enter the hilum of the spleen. As the splenic artery passes along the superior border of the pancreas, it gives off numerous small branches to supply the neck, body, and tail of the pancreas (Fig. 4.124). Approaching the spleen, the splenic artery gives off short gastric arteries, which pass through the gastrosplenic ligament to supply the fundus of the stomach. It also gives off the left gastro-omental artery, which runs to the right along the greater curvature of the stomach, and anastomoses with the right gastro-omental artery. The common hepatic artery is a medium-sized branch of the celiac trunk that runs to the right and divides into its two terminal branches, the hepatic artery proper and the gastroduodenal artery (Figs. 4.123 and 4.124).	Anatomy_Gray. The splenic artery, the largest branch of the celiac trunk, takes a tortuous course to the left along the superior border of the pancreas (Fig. 4.123). It travels in the splenorenal ligament and divides into numerous branches, which enter the hilum of the spleen. As the splenic artery passes along the superior border of the pancreas, it gives off numerous small branches to supply the neck, body, and tail of the pancreas (Fig. 4.124). Approaching the spleen, the splenic artery gives off short gastric arteries, which pass through the gastrosplenic ligament to supply the fundus of the stomach. It also gives off the left gastro-omental artery, which runs to the right along the greater curvature of the stomach, and anastomoses with the right gastro-omental artery. The common hepatic artery is a medium-sized branch of the celiac trunk that runs to the right and divides into its two terminal branches, the hepatic artery proper and the gastroduodenal artery (Figs. 4.123 and 4.124).
Anatomy_Gray_712	Anatomy_Gray	The hepatic artery proper ascends toward the liver in the free edge of the lesser omentum. It runs to the left of the bile duct and anterior to the portal vein, and divides into the right and left hepatic arteries near the porta hepatis (Fig. 4.125). As the right hepatic artery nears the liver, it gives off the cystic artery to the gallbladder. The right gastric artery often originates from the hepatic artery proper but it can also arise from the common hepatic artery or from the left hepatic, gastroduodenal, or supraduodenal arteries. It courses to the left and ascends along the lesser curvature of the stomach in the lesser omentum, supplies adjacent areas of the stomach, and anastomoses with the left gastric artery.	Anatomy_Gray. The hepatic artery proper ascends toward the liver in the free edge of the lesser omentum. It runs to the left of the bile duct and anterior to the portal vein, and divides into the right and left hepatic arteries near the porta hepatis (Fig. 4.125). As the right hepatic artery nears the liver, it gives off the cystic artery to the gallbladder. The right gastric artery often originates from the hepatic artery proper but it can also arise from the common hepatic artery or from the left hepatic, gastroduodenal, or supraduodenal arteries. It courses to the left and ascends along the lesser curvature of the stomach in the lesser omentum, supplies adjacent areas of the stomach, and anastomoses with the left gastric artery.
Anatomy_Gray_713	Anatomy_Gray	The gastroduodenal artery may give off the supraduodenal artery and does give off the posterior superior pancreaticoduodenal artery near the upper border of the superior part of the duodenum. After these branch the gastroduodenal artery continues descending posterior to the superior part of the duodenum. Reaching the lower border of the superior part of the duodenum, the gastroduodenal artery divides into its terminal branches, the right gastro-omental artery and the anterior superior pancreaticoduodenal artery (Fig. 4.124). The right gastro-omental artery passes to the left, along the greater curvature of the stomach, eventually anastomosing with the left gastro-omental artery from the splenic artery. The right gastro-omental artery sends branches to both surfaces of the stomach and additional branches descend into the greater omentum.	Anatomy_Gray. The gastroduodenal artery may give off the supraduodenal artery and does give off the posterior superior pancreaticoduodenal artery near the upper border of the superior part of the duodenum. After these branch the gastroduodenal artery continues descending posterior to the superior part of the duodenum. Reaching the lower border of the superior part of the duodenum, the gastroduodenal artery divides into its terminal branches, the right gastro-omental artery and the anterior superior pancreaticoduodenal artery (Fig. 4.124). The right gastro-omental artery passes to the left, along the greater curvature of the stomach, eventually anastomosing with the left gastro-omental artery from the splenic artery. The right gastro-omental artery sends branches to both surfaces of the stomach and additional branches descend into the greater omentum.
Anatomy_Gray_714	Anatomy_Gray	The anterior superior pancreaticoduodenal artery descends and, along with the posterior superior pancreaticoduodenal artery, supplies the head of the pancreas and the duodenum (Fig. 4.124). These vessels eventually anastomose with the anterior and posterior branches of the inferior pancreaticoduodenal artery. The superior mesenteric artery is the anterior branch of the abdominal aorta supplying the midgut. It arises from the abdominal aorta immediately below the celiac artery (Fig. 4.126), anterior to the lower part of vertebra LI.	Anatomy_Gray. The anterior superior pancreaticoduodenal artery descends and, along with the posterior superior pancreaticoduodenal artery, supplies the head of the pancreas and the duodenum (Fig. 4.124). These vessels eventually anastomose with the anterior and posterior branches of the inferior pancreaticoduodenal artery. The superior mesenteric artery is the anterior branch of the abdominal aorta supplying the midgut. It arises from the abdominal aorta immediately below the celiac artery (Fig. 4.126), anterior to the lower part of vertebra LI.
Anatomy_Gray_715	Anatomy_Gray	The superior mesenteric artery is crossed anteriorly by the splenic vein and the neck of the pancreas. Posterior to the artery are the left renal vein, the uncinate process of the pancreas, and the inferior part of the duodenum. After giving off its first branch (the inferior pancreaticoduodenal artery), the superior mesenteric artery gives off jejunal and ileal arteries on its left (Fig. 4.126). Branching from the right side of the main trunk of the superior mesenteric artery are three vessels—the middle colic, right colic, and ileocolic arteries—which supply the terminal ileum, cecum, ascending colon, and two-thirds of the transverse colon.	Anatomy_Gray. The superior mesenteric artery is crossed anteriorly by the splenic vein and the neck of the pancreas. Posterior to the artery are the left renal vein, the uncinate process of the pancreas, and the inferior part of the duodenum. After giving off its first branch (the inferior pancreaticoduodenal artery), the superior mesenteric artery gives off jejunal and ileal arteries on its left (Fig. 4.126). Branching from the right side of the main trunk of the superior mesenteric artery are three vessels—the middle colic, right colic, and ileocolic arteries—which supply the terminal ileum, cecum, ascending colon, and two-thirds of the transverse colon.
Anatomy_Gray_716	Anatomy_Gray	The inferior pancreaticoduodenal artery is the first branch of the superior mesenteric artery. It divides immediately into anterior and posterior branches, which ascend on the corresponding sides of the head of the pancreas. Superiorly, these arteries anastomose with anterior and posterior superior pancreaticoduodenal arteries (see Figs. 4.125 and 4.126). This arterial network supplies the head and uncinate process of the pancreas and the duodenum. Distal to the inferior pancreaticoduodenal artery, the superior mesenteric artery gives off numerous branches. Arising on the left is a large number of jejunal and ileal arteries supplying the jejunum and most of the ileum (Fig. 4.127). These branches leave the main trunk of the artery, pass between two layers of the mesentery, and form anastomosing arches or arcades as they pass outward to supply the small intestine. The number of arterial arcades increases distally along the gut.	Anatomy_Gray. The inferior pancreaticoduodenal artery is the first branch of the superior mesenteric artery. It divides immediately into anterior and posterior branches, which ascend on the corresponding sides of the head of the pancreas. Superiorly, these arteries anastomose with anterior and posterior superior pancreaticoduodenal arteries (see Figs. 4.125 and 4.126). This arterial network supplies the head and uncinate process of the pancreas and the duodenum. Distal to the inferior pancreaticoduodenal artery, the superior mesenteric artery gives off numerous branches. Arising on the left is a large number of jejunal and ileal arteries supplying the jejunum and most of the ileum (Fig. 4.127). These branches leave the main trunk of the artery, pass between two layers of the mesentery, and form anastomosing arches or arcades as they pass outward to supply the small intestine. The number of arterial arcades increases distally along the gut.
Anatomy_Gray_717	Anatomy_Gray	There may be single and then double arcades in the area of the jejunum, with a continued increase in the number of arcades moving into and through the area of the ileum. Extending from the terminal arcade are vasa recta (straight arteries), which provide the final direct vascular supply to the walls of the small intestine. The vasa recta supplying the jejunum are usually long and close together, forming narrow windows visible in the mesentery. The vasa recta supplying the ileum are generally short and far apart, forming low broad windows.	Anatomy_Gray. There may be single and then double arcades in the area of the jejunum, with a continued increase in the number of arcades moving into and through the area of the ileum. Extending from the terminal arcade are vasa recta (straight arteries), which provide the final direct vascular supply to the walls of the small intestine. The vasa recta supplying the jejunum are usually long and close together, forming narrow windows visible in the mesentery. The vasa recta supplying the ileum are generally short and far apart, forming low broad windows.
Anatomy_Gray_718	Anatomy_Gray	The middle colic artery is the first of the three branches from the right side of the main trunk of the superior mesenteric artery (Fig. 4.127). Arising as the superior mesenteric artery emerges from beneath the pancreas, the middle colic artery enters the transverse mesocolon and divides into right and left branches. The right branch anastomoses with the right colic artery while the left branch anastomoses with the left colic artery, which is a branch of the inferior mesenteric artery.	Anatomy_Gray. The middle colic artery is the first of the three branches from the right side of the main trunk of the superior mesenteric artery (Fig. 4.127). Arising as the superior mesenteric artery emerges from beneath the pancreas, the middle colic artery enters the transverse mesocolon and divides into right and left branches. The right branch anastomoses with the right colic artery while the left branch anastomoses with the left colic artery, which is a branch of the inferior mesenteric artery.
Anatomy_Gray_719	Anatomy_Gray	Continuing distally along the main trunk of the superior mesenteric artery, the right colic artery is the second of the three branches from the right side of the main trunk of the superior mesenteric artery (Fig. 4.126). It is an inconsistent branch, and passes to the right in a retroperitoneal position to supply the ascending colon. Nearing the colon, it divides into a descending branch, which anastomoses with the ileocolic artery, and an ascending branch, which anastomoses with the middle colic artery. The final branch arising from the right side of the superior mesenteric artery is the ileocolic artery (Fig. 4.127). This passes downward and to the right toward the right iliac fossa where it divides into superior and inferior branches: The superior branch passes upward along the ascending colon to anastomose with the right colic artery. The inferior branch continues toward the ileocolic junction, dividing into colic, cecal, appendicular, and ileal branches (Fig. 4.127).	Anatomy_Gray. Continuing distally along the main trunk of the superior mesenteric artery, the right colic artery is the second of the three branches from the right side of the main trunk of the superior mesenteric artery (Fig. 4.126). It is an inconsistent branch, and passes to the right in a retroperitoneal position to supply the ascending colon. Nearing the colon, it divides into a descending branch, which anastomoses with the ileocolic artery, and an ascending branch, which anastomoses with the middle colic artery. The final branch arising from the right side of the superior mesenteric artery is the ileocolic artery (Fig. 4.127). This passes downward and to the right toward the right iliac fossa where it divides into superior and inferior branches: The superior branch passes upward along the ascending colon to anastomose with the right colic artery. The inferior branch continues toward the ileocolic junction, dividing into colic, cecal, appendicular, and ileal branches (Fig. 4.127).
Anatomy_Gray_720	Anatomy_Gray	The inferior branch continues toward the ileocolic junction, dividing into colic, cecal, appendicular, and ileal branches (Fig. 4.127). The specific pattern of distribution and origin of these branches is variable: The colic branch crosses to the ascending colon and passes upward to supply the first part of the ascending colon. Anterior and posterior cecal branches, arising either as a common trunk or as separate branches, supply corresponding sides of the cecum. The appendicular branch enters the free margin of and supplies the mesoappendix and the appendix. The ileal branch passes to the left and ascends to supply the final part of the ileum before anastomosing with the superior mesenteric artery.	Anatomy_Gray. The inferior branch continues toward the ileocolic junction, dividing into colic, cecal, appendicular, and ileal branches (Fig. 4.127). The specific pattern of distribution and origin of these branches is variable: The colic branch crosses to the ascending colon and passes upward to supply the first part of the ascending colon. Anterior and posterior cecal branches, arising either as a common trunk or as separate branches, supply corresponding sides of the cecum. The appendicular branch enters the free margin of and supplies the mesoappendix and the appendix. The ileal branch passes to the left and ascends to supply the final part of the ileum before anastomosing with the superior mesenteric artery.
Anatomy_Gray_721	Anatomy_Gray	The ileal branch passes to the left and ascends to supply the final part of the ileum before anastomosing with the superior mesenteric artery. The inferior mesenteric artery is the anterior branch of the abdominal aorta that supplies the hindgut. It is the smallest of the three anterior branches of the abdominal aorta and arises anterior to the body of vertebra LIII. Initially, the inferior mesenteric artery descends anteriorly to the aorta and then passes to the left as it continues inferiorly (Fig. 4.128). Its branches include the left colic artery, several sigmoid arteries, and the superior rectal artery. The left colic artery is the first branch of the inferior mesenteric artery (Fig. 4.128). It ascends retroperitoneally, dividing into ascending and descending branches:	Anatomy_Gray. The ileal branch passes to the left and ascends to supply the final part of the ileum before anastomosing with the superior mesenteric artery. The inferior mesenteric artery is the anterior branch of the abdominal aorta that supplies the hindgut. It is the smallest of the three anterior branches of the abdominal aorta and arises anterior to the body of vertebra LIII. Initially, the inferior mesenteric artery descends anteriorly to the aorta and then passes to the left as it continues inferiorly (Fig. 4.128). Its branches include the left colic artery, several sigmoid arteries, and the superior rectal artery. The left colic artery is the first branch of the inferior mesenteric artery (Fig. 4.128). It ascends retroperitoneally, dividing into ascending and descending branches:
Anatomy_Gray_722	Anatomy_Gray	The left colic artery is the first branch of the inferior mesenteric artery (Fig. 4.128). It ascends retroperitoneally, dividing into ascending and descending branches: The ascending branch passes anteriorly to the left kidney, then enters the transverse mesocolon, and passes superiorly to supply the upper part of the descending colon and the distal part of the transverse colon; it anastomoses with branches of the middle colic artery. The descending branch passes inferiorly, supplying the lower part of the descending colon, and anastomoses with the first sigmoid artery. The sigmoid arteries consist of two to four branches, which descend to the left, in the sigmoid mesocolon, to supply the lowest part of the descending colon and the sigmoid colon (Fig. 4.128). These branches anastomose superiorly with branches from the left colic artery and inferiorly with branches from the superior rectal artery.	Anatomy_Gray. The left colic artery is the first branch of the inferior mesenteric artery (Fig. 4.128). It ascends retroperitoneally, dividing into ascending and descending branches: The ascending branch passes anteriorly to the left kidney, then enters the transverse mesocolon, and passes superiorly to supply the upper part of the descending colon and the distal part of the transverse colon; it anastomoses with branches of the middle colic artery. The descending branch passes inferiorly, supplying the lower part of the descending colon, and anastomoses with the first sigmoid artery. The sigmoid arteries consist of two to four branches, which descend to the left, in the sigmoid mesocolon, to supply the lowest part of the descending colon and the sigmoid colon (Fig. 4.128). These branches anastomose superiorly with branches from the left colic artery and inferiorly with branches from the superior rectal artery.
Anatomy_Gray_723	Anatomy_Gray	The terminal branch of the inferior mesenteric artery is the superior rectal artery (Fig. 4.128). This vessel descends into the pelvic cavity in the sigmoid mesocolon, crossing the left common iliac vessels. Opposite vertebra SIII, the superior rectal artery divides. The two terminal branches descend on each side of the rectum, dividing into smaller branches in the wall of the rectum. These smaller branches continue inferiorly to the level of the internal anal sphincter, anastomosing along the way with branches from the middle rectal arteries (from the internal iliac artery) and the inferior rectal arteries (from the internal pudendal artery).	Anatomy_Gray. The terminal branch of the inferior mesenteric artery is the superior rectal artery (Fig. 4.128). This vessel descends into the pelvic cavity in the sigmoid mesocolon, crossing the left common iliac vessels. Opposite vertebra SIII, the superior rectal artery divides. The two terminal branches descend on each side of the rectum, dividing into smaller branches in the wall of the rectum. These smaller branches continue inferiorly to the level of the internal anal sphincter, anastomosing along the way with branches from the middle rectal arteries (from the internal iliac artery) and the inferior rectal arteries (from the internal pudendal artery).
Anatomy_Gray_724	Anatomy_Gray	Venous drainage of the spleen, pancreas, gallbladder, and abdominal part of the gastrointestinal tract, except for the inferior part of the rectum, is through the portal system of veins, which deliver blood from these structures to the liver. Once blood passes through the hepatic sinusoids, it passes through progressively larger veins until it enters the hepatic veins, which return the venous blood to the inferior vena cava just inferior to the diaphragm. The portal vein is the final common pathway for the transport of venous blood from the spleen, pancreas, gallbladder, and abdominal part of the gastrointestinal tract. It is formed by the union of the splenic vein and the superior mesenteric vein posterior to the neck of the pancreas at the level of vertebra LII (Fig. 4.131).	Anatomy_Gray. Venous drainage of the spleen, pancreas, gallbladder, and abdominal part of the gastrointestinal tract, except for the inferior part of the rectum, is through the portal system of veins, which deliver blood from these structures to the liver. Once blood passes through the hepatic sinusoids, it passes through progressively larger veins until it enters the hepatic veins, which return the venous blood to the inferior vena cava just inferior to the diaphragm. The portal vein is the final common pathway for the transport of venous blood from the spleen, pancreas, gallbladder, and abdominal part of the gastrointestinal tract. It is formed by the union of the splenic vein and the superior mesenteric vein posterior to the neck of the pancreas at the level of vertebra LII (Fig. 4.131).
Anatomy_Gray_725	Anatomy_Gray	Ascending toward the liver, the portal vein passes posterior to the superior part of the duodenum and enters the right margin of the lesser omentum. As it passes through this part of the lesser omentum, it is anterior to the omental foramen and posterior to both the bile duct, which is slightly to its right, and the hepatic artery proper, which is slightly to its left (see Fig. 4.125, p. 347). On approaching the liver, the portal vein divides into right and left branches, which enter the liver parenchyma. Tributaries to the portal vein include: right and left gastric veins draining the lesser curvature of the stomach and abdominal esophagus, cystic veins from the gallbladder, and the para-umbilical veins, which are associated with the obliterated umbilical vein and connect to veins on the anterior abdominal wall (Fig. 4.133 on p. 357).	Anatomy_Gray. Ascending toward the liver, the portal vein passes posterior to the superior part of the duodenum and enters the right margin of the lesser omentum. As it passes through this part of the lesser omentum, it is anterior to the omental foramen and posterior to both the bile duct, which is slightly to its right, and the hepatic artery proper, which is slightly to its left (see Fig. 4.125, p. 347). On approaching the liver, the portal vein divides into right and left branches, which enter the liver parenchyma. Tributaries to the portal vein include: right and left gastric veins draining the lesser curvature of the stomach and abdominal esophagus, cystic veins from the gallbladder, and the para-umbilical veins, which are associated with the obliterated umbilical vein and connect to veins on the anterior abdominal wall (Fig. 4.133 on p. 357).
Anatomy_Gray_726	Anatomy_Gray	The splenic vein forms from numerous smaller vessels leaving the hilum of the spleen (Fig. 4.132). It passes to the right, passing through the splenorenal ligament with the splenic artery and the tail of the pancreas. Continuing to the right, the large, straight splenic vein is in contact with the body of the pancreas as it crosses the posterior abdominal wall. Posterior to the neck of the pancreas, the splenic vein joins the superior mesenteric vein to form the portal vein. Tributaries to the splenic vein include: short gastric veins from the fundus and left part of the greater curvature of the stomach, the left gastro-omental vein from the greater curvature of the stomach, pancreatic veins draining the body and tail of the pancreas, and usually the inferior mesenteric vein.	Anatomy_Gray. The splenic vein forms from numerous smaller vessels leaving the hilum of the spleen (Fig. 4.132). It passes to the right, passing through the splenorenal ligament with the splenic artery and the tail of the pancreas. Continuing to the right, the large, straight splenic vein is in contact with the body of the pancreas as it crosses the posterior abdominal wall. Posterior to the neck of the pancreas, the splenic vein joins the superior mesenteric vein to form the portal vein. Tributaries to the splenic vein include: short gastric veins from the fundus and left part of the greater curvature of the stomach, the left gastro-omental vein from the greater curvature of the stomach, pancreatic veins draining the body and tail of the pancreas, and usually the inferior mesenteric vein.
Anatomy_Gray_727	Anatomy_Gray	The superior mesenteric vein drains blood from the small intestine, cecum, ascending colon, and transverse colon (Fig. 4.132). It begins in the right iliac fossa as veins draining the terminal ileum, cecum, and appendix join, and ascends in the mesentery to the right of the superior mesenteric artery. Posterior to the neck of the pancreas, the superior mesenteric vein joins the splenic vein to form the portal vein.	Anatomy_Gray. The superior mesenteric vein drains blood from the small intestine, cecum, ascending colon, and transverse colon (Fig. 4.132). It begins in the right iliac fossa as veins draining the terminal ileum, cecum, and appendix join, and ascends in the mesentery to the right of the superior mesenteric artery. Posterior to the neck of the pancreas, the superior mesenteric vein joins the splenic vein to form the portal vein.
Anatomy_Gray_728	Anatomy_Gray	Posterior to the neck of the pancreas, the superior mesenteric vein joins the splenic vein to form the portal vein. As a corresponding vein accompanies each branch of the superior mesenteric artery, tributaries to the superior mesenteric vein include jejunal, ileal, ileocolic, right colic, and middle colic veins. Additional tributaries include: the right gastro-omental vein, draining the right part of the greater curvature of the stomach, and the anterior and posterior inferior pancreaticoduodenal veins, which pass alongside the arteries of the same name; the anterior superior pancreaticoduodenal vein usually empties into the right gastro-omental vein, and the posterior superior pancreaticoduodenal vein usually empties directly into the portal vein.	Anatomy_Gray. Posterior to the neck of the pancreas, the superior mesenteric vein joins the splenic vein to form the portal vein. As a corresponding vein accompanies each branch of the superior mesenteric artery, tributaries to the superior mesenteric vein include jejunal, ileal, ileocolic, right colic, and middle colic veins. Additional tributaries include: the right gastro-omental vein, draining the right part of the greater curvature of the stomach, and the anterior and posterior inferior pancreaticoduodenal veins, which pass alongside the arteries of the same name; the anterior superior pancreaticoduodenal vein usually empties into the right gastro-omental vein, and the posterior superior pancreaticoduodenal vein usually empties directly into the portal vein.
Anatomy_Gray_729	Anatomy_Gray	The inferior mesenteric vein drains blood from the rectum, sigmoid colon, descending colon, and splenic flexure (Fig. 4.132). It begins as the superior rectal vein and ascends, receiving tributaries from the sigmoid veins and the left colic vein. All these veins accompany arteries of the same name. Continuing to ascend, the inferior mesenteric vein passes posterior to the body of the pancreas and usually joins the splenic vein. Occasionally, it ends at the junction of the splenic and superior mesenteric veins or joins the superior mesenteric vein.	Anatomy_Gray. The inferior mesenteric vein drains blood from the rectum, sigmoid colon, descending colon, and splenic flexure (Fig. 4.132). It begins as the superior rectal vein and ascends, receiving tributaries from the sigmoid veins and the left colic vein. All these veins accompany arteries of the same name. Continuing to ascend, the inferior mesenteric vein passes posterior to the body of the pancreas and usually joins the splenic vein. Occasionally, it ends at the junction of the splenic and superior mesenteric veins or joins the superior mesenteric vein.
Anatomy_Gray_730	Anatomy_Gray	Lymphatic drainage of the abdominal part of the gastrointestinal tract, as low as the inferior part of the rectum, as well as the spleen, pancreas, gallbladder, and liver, is through vessels and nodes that eventually end in large collections of pre-aortic lymph nodes at the origins of the three anterior branches of the abdominal aorta, which supply these structures. These collections are therefore referred to as the celiac, superior mesenteric, and inferior mesenteric groups of pre-aortic lymph nodes. Lymph from viscera is supplied by three routes: The celiac trunk (i.e., structures that are part of the abdominal foregut) drains to pre-aortic nodes near the origin of the celiac trunk (Fig. 4.134)—these celiac nodes also receive lymph from the superior mesenteric and inferior mesenteric groups of pre-aortic nodes, and lymph from the celiac nodes enters the cisterna chyli.	Anatomy_Gray. Lymphatic drainage of the abdominal part of the gastrointestinal tract, as low as the inferior part of the rectum, as well as the spleen, pancreas, gallbladder, and liver, is through vessels and nodes that eventually end in large collections of pre-aortic lymph nodes at the origins of the three anterior branches of the abdominal aorta, which supply these structures. These collections are therefore referred to as the celiac, superior mesenteric, and inferior mesenteric groups of pre-aortic lymph nodes. Lymph from viscera is supplied by three routes: The celiac trunk (i.e., structures that are part of the abdominal foregut) drains to pre-aortic nodes near the origin of the celiac trunk (Fig. 4.134)—these celiac nodes also receive lymph from the superior mesenteric and inferior mesenteric groups of pre-aortic nodes, and lymph from the celiac nodes enters the cisterna chyli.
Anatomy_Gray_731	Anatomy_Gray	The superior mesenteric artery (i.e., structures that are part of the abdominal midgut) drains to pre-aortic nodes near the origin of the superior mesenteric artery (Fig. 4.134)—these superior mesenteric nodes also receive lymph from the inferior mesenteric groups of pre-aortic nodes, and lymph from the superior mesenteric nodes drains to the celiac nodes. The inferior mesenteric artery (i.e., structures that are part of the abdominal hindgut) drains to pre-aortic nodes near the origin of the inferior mesenteric artery (Fig. 4.134), and lymph from the inferior mesenteric nodes drains to the superior mesenteric nodes. Abdominal viscera are innervated by both extrinsic and intrinsic components of the nervous system: Extrinsic innervation involves receiving motor impulses from, and sending sensory information to, the central nervous system.	Anatomy_Gray. The superior mesenteric artery (i.e., structures that are part of the abdominal midgut) drains to pre-aortic nodes near the origin of the superior mesenteric artery (Fig. 4.134)—these superior mesenteric nodes also receive lymph from the inferior mesenteric groups of pre-aortic nodes, and lymph from the superior mesenteric nodes drains to the celiac nodes. The inferior mesenteric artery (i.e., structures that are part of the abdominal hindgut) drains to pre-aortic nodes near the origin of the inferior mesenteric artery (Fig. 4.134), and lymph from the inferior mesenteric nodes drains to the superior mesenteric nodes. Abdominal viscera are innervated by both extrinsic and intrinsic components of the nervous system: Extrinsic innervation involves receiving motor impulses from, and sending sensory information to, the central nervous system.
Anatomy_Gray_732	Anatomy_Gray	Extrinsic innervation involves receiving motor impulses from, and sending sensory information to, the central nervous system. Intrinsic innervation involves the regulation of digestive tract activities by a generally self-sufficient network of sensory and motor neurons (the enteric nervous system). Abdominal viscera receiving extrinsic innervation include the abdominal part of the gastrointestinal tract, the spleen, the pancreas, the gallbladder, and the liver. These viscera send sensory information back to the central nervous system through visceral afferent fibers and receive motor impulses from the central nervous system through visceral efferent fibers. The visceral efferent fibers are part of the sympathetic and parasympathetic parts of the autonomic division of the peripheral nervous system.	Anatomy_Gray. Extrinsic innervation involves receiving motor impulses from, and sending sensory information to, the central nervous system. Intrinsic innervation involves the regulation of digestive tract activities by a generally self-sufficient network of sensory and motor neurons (the enteric nervous system). Abdominal viscera receiving extrinsic innervation include the abdominal part of the gastrointestinal tract, the spleen, the pancreas, the gallbladder, and the liver. These viscera send sensory information back to the central nervous system through visceral afferent fibers and receive motor impulses from the central nervous system through visceral efferent fibers. The visceral efferent fibers are part of the sympathetic and parasympathetic parts of the autonomic division of the peripheral nervous system.
Anatomy_Gray_733	Anatomy_Gray	The visceral efferent fibers are part of the sympathetic and parasympathetic parts of the autonomic division of the peripheral nervous system. Structural components serving as conduits for these afferent and efferent fibers include posterior and anterior roots of the spinal cord, respectively, spinal nerves, anterior rami, white and gray rami communicantes, the sympathetic trunks, splanchnic nerves carrying sympathetic fibers (thoracic, lumbar, and sacral), parasympathetic fibers (pelvic), the prevertebral plexus and related ganglia, and the vagus nerves [X]. The enteric nervous system consists of motor and sensory neurons in two interconnected plexuses in the walls of the gastrointestinal tract. These neurons control the coordinated contraction and relaxation of intestinal smooth muscle and regulate gastric secretion and blood flow.	Anatomy_Gray. The visceral efferent fibers are part of the sympathetic and parasympathetic parts of the autonomic division of the peripheral nervous system. Structural components serving as conduits for these afferent and efferent fibers include posterior and anterior roots of the spinal cord, respectively, spinal nerves, anterior rami, white and gray rami communicantes, the sympathetic trunks, splanchnic nerves carrying sympathetic fibers (thoracic, lumbar, and sacral), parasympathetic fibers (pelvic), the prevertebral plexus and related ganglia, and the vagus nerves [X]. The enteric nervous system consists of motor and sensory neurons in two interconnected plexuses in the walls of the gastrointestinal tract. These neurons control the coordinated contraction and relaxation of intestinal smooth muscle and regulate gastric secretion and blood flow.
Anatomy_Gray_734	Anatomy_Gray	The sympathetic trunks are two parallel nerve cords extending on either side of the vertebral column from the base of the skull to the coccyx (Fig. 4.135). As they pass through the neck, they lie posterior to the carotid sheath. In the upper thorax, they are anterior to the necks of the ribs, while in the lower thorax they are on the lateral aspect of the vertebral bodies. In the abdomen, they are anterolateral to the lumbar vertebral bodies and, continuing into the pelvis, they are anterior to the sacrum. The two sympathetic trunks come together anterior to the coccyx to form the ganglion impar.	Anatomy_Gray. The sympathetic trunks are two parallel nerve cords extending on either side of the vertebral column from the base of the skull to the coccyx (Fig. 4.135). As they pass through the neck, they lie posterior to the carotid sheath. In the upper thorax, they are anterior to the necks of the ribs, while in the lower thorax they are on the lateral aspect of the vertebral bodies. In the abdomen, they are anterolateral to the lumbar vertebral bodies and, continuing into the pelvis, they are anterior to the sacrum. The two sympathetic trunks come together anterior to the coccyx to form the ganglion impar.
Anatomy_Gray_735	Anatomy_Gray	Throughout the extent of the sympathetic trunks, small raised areas are visible. These collections of neuronal cell bodies outside the CNS are the paravertebral sympathetic ganglia. There are usually: three ganglia in the cervical region, eleven or twelve ganglia in the thoracic region, four ganglia in the lumbar region, four or five ganglia in the sacral region, and the ganglion impar anterior to the coccyx (Fig. 4.135). The ganglia and trunks are connected to adjacent spinal nerves by gray rami communicantes throughout the length of the sympathetic trunk and by white rami communicantes in the thoracic and upper lumbar parts of the trunk (T1 to L2). Neuronal fibers found in the sympathetic trunks include preganglionic and postganglionic sympathetic fibers and visceral afferent fibers.	Anatomy_Gray. Throughout the extent of the sympathetic trunks, small raised areas are visible. These collections of neuronal cell bodies outside the CNS are the paravertebral sympathetic ganglia. There are usually: three ganglia in the cervical region, eleven or twelve ganglia in the thoracic region, four ganglia in the lumbar region, four or five ganglia in the sacral region, and the ganglion impar anterior to the coccyx (Fig. 4.135). The ganglia and trunks are connected to adjacent spinal nerves by gray rami communicantes throughout the length of the sympathetic trunk and by white rami communicantes in the thoracic and upper lumbar parts of the trunk (T1 to L2). Neuronal fibers found in the sympathetic trunks include preganglionic and postganglionic sympathetic fibers and visceral afferent fibers.
Anatomy_Gray_736	Anatomy_Gray	The splanchnic nerves are important components in the innervation of the abdominal viscera. They pass from the sympathetic trunk or sympathetic ganglia associated with the trunk, to the prevertebral plexus and ganglia anterior to the abdominal aorta. There are two different types of splanchnic nerves, depending on the type of visceral efferent fiber they are carrying: The thoracic, lumbar, and sacral splanchnic nerves carry preganglionic sympathetic fibers from the sympathetic trunk to ganglia in the prevertebral plexus, and also visceral afferent fibers. The pelvic splanchnic nerves carry preganglionic parasympathetic fibers from anterior rami of S2, S3, and S4 spinal nerves to an extension of the prevertebral plexus in the pelvis (the inferior hypogastric plexus or pelvic plexus).	Anatomy_Gray. The splanchnic nerves are important components in the innervation of the abdominal viscera. They pass from the sympathetic trunk or sympathetic ganglia associated with the trunk, to the prevertebral plexus and ganglia anterior to the abdominal aorta. There are two different types of splanchnic nerves, depending on the type of visceral efferent fiber they are carrying: The thoracic, lumbar, and sacral splanchnic nerves carry preganglionic sympathetic fibers from the sympathetic trunk to ganglia in the prevertebral plexus, and also visceral afferent fibers. The pelvic splanchnic nerves carry preganglionic parasympathetic fibers from anterior rami of S2, S3, and S4 spinal nerves to an extension of the prevertebral plexus in the pelvis (the inferior hypogastric plexus or pelvic plexus).
Anatomy_Gray_737	Anatomy_Gray	Three thoracic splanchnic nerves pass from sympathetic ganglia along the sympathetic trunk in the thorax to the prevertebral plexus and ganglia associated with the abdominal aorta in the abdomen (Fig. 4.136): The greater splanchnic nerve arises from the fifth to the ninth (or tenth) thoracic ganglia and travels to the celiac ganglion in the abdomen (a prevertebral ganglion associated with the celiac trunk). The lesser splanchnic nerve arises from the ninth and tenth (or tenth and eleventh) thoracic ganglia and travels to the aorticorenal ganglion. The least splanchnic nerve, when present, arises from the twelfth thoracic ganglion and travels to the renal plexus. There are usually two to four lumbar splanchnic nerves, which pass from the lumbar part of the sympathetic trunk or associated ganglia and enter the prevertebral plexus (Fig. 4.136).	Anatomy_Gray. Three thoracic splanchnic nerves pass from sympathetic ganglia along the sympathetic trunk in the thorax to the prevertebral plexus and ganglia associated with the abdominal aorta in the abdomen (Fig. 4.136): The greater splanchnic nerve arises from the fifth to the ninth (or tenth) thoracic ganglia and travels to the celiac ganglion in the abdomen (a prevertebral ganglion associated with the celiac trunk). The lesser splanchnic nerve arises from the ninth and tenth (or tenth and eleventh) thoracic ganglia and travels to the aorticorenal ganglion. The least splanchnic nerve, when present, arises from the twelfth thoracic ganglion and travels to the renal plexus. There are usually two to four lumbar splanchnic nerves, which pass from the lumbar part of the sympathetic trunk or associated ganglia and enter the prevertebral plexus (Fig. 4.136).
Anatomy_Gray_738	Anatomy_Gray	There are usually two to four lumbar splanchnic nerves, which pass from the lumbar part of the sympathetic trunk or associated ganglia and enter the prevertebral plexus (Fig. 4.136). Similarly, the sacral splanchnic nerves pass from the sacral part of the sympathetic trunk or associated ganglia and enter the inferior hypogastric plexus, which is an extension of the prevertebral plexus into the pelvis.	Anatomy_Gray. There are usually two to four lumbar splanchnic nerves, which pass from the lumbar part of the sympathetic trunk or associated ganglia and enter the prevertebral plexus (Fig. 4.136). Similarly, the sacral splanchnic nerves pass from the sacral part of the sympathetic trunk or associated ganglia and enter the inferior hypogastric plexus, which is an extension of the prevertebral plexus into the pelvis.
Anatomy_Gray_739	Anatomy_Gray	The pelvic splanchnic nerves (parasympathetic root) are unique. They are the only splanchnic nerves that carry parasympathetic fibers. In other words, they do not originate from the sympathetic trunks. Rather, they originate directly from the anterior rami of S2 to S4. Preganglionic parasympathetic fibers originating in the sacral spinal cord pass from the S2 to S4 spinal nerves to the inferior hypogastric plexus (Fig. 4.136). Once in this plexus, some of these fibers pass upward, enter the abdominal prevertebral plexus, and distribute with the arteries supplying the hindgut. This provides the pathway for innervation of the distal one-third of the transverse colon, the descending colon, and the sigmoid colon by preganglionic parasympathetic fibers.	Anatomy_Gray. The pelvic splanchnic nerves (parasympathetic root) are unique. They are the only splanchnic nerves that carry parasympathetic fibers. In other words, they do not originate from the sympathetic trunks. Rather, they originate directly from the anterior rami of S2 to S4. Preganglionic parasympathetic fibers originating in the sacral spinal cord pass from the S2 to S4 spinal nerves to the inferior hypogastric plexus (Fig. 4.136). Once in this plexus, some of these fibers pass upward, enter the abdominal prevertebral plexus, and distribute with the arteries supplying the hindgut. This provides the pathway for innervation of the distal one-third of the transverse colon, the descending colon, and the sigmoid colon by preganglionic parasympathetic fibers.