Anatomy_Gray

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

Anatomy_Gray. The abdominal prevertebral plexus is a collection of nerve fibers that surrounds the abdominal aorta and is continuous onto its major branches. Scattered throughout the length of the abdominal prevertebral plexus are cell bodies of postganglionic sympathetic fibers. Some of these cell bodies are organized into distinct ganglia, while others are more random in their distribution. The ganglia are usually associated with specific branches of the abdominal aorta and named after these branches. The three major divisions of the abdominal prevertebral plexus and associated ganglia are the celiac, aortic, and superior hypogastric plexuses (Fig. 4.137). The celiac plexus is the large accumulation of nerve fibers and ganglia associated with the roots of the celiac trunk and superior mesenteric artery immediately below the aortic hiatus of the diaphragm. Ganglia associated with the celiac plexus include two celiac ganglia, a single superior mesenteric ganglion, and two aorticorenal ganglia.


Anatomy_Gray

Anatomy_Gray. The aortic plexus consists of nerve fibers and associated ganglia on the anterior and lateral surfaces of the abdominal aorta extending from just below the origin of the superior mesenteric artery to the bifurcation of the aorta into the two common iliac arteries. The major ganglion in this plexus is the inferior mesenteric ganglion at the root of the inferior mesenteric artery. The superior hypogastric plexus contains numerous small ganglia and is the final part of the abdominal prevertebral plexus before the prevertebral plexus continues into the pelvic cavity.


Anatomy_Gray

Anatomy_Gray. The superior hypogastric plexus contains numerous small ganglia and is the final part of the abdominal prevertebral plexus before the prevertebral plexus continues into the pelvic cavity. Each of these major plexuses gives origin to a number of secondary plexuses, which may also contain small ganglia. These plexuses are usually named after the vessels with which they are associated. For example, the celiac plexus is usually described as giving origin to the superior mesenteric plexus and the renal plexus, as well as other plexuses that extend out along the various branches of the celiac trunk. Similarly, the aortic plexus has secondary plexuses consisting of the inferior mesenteric plexus, the spermatic plexus, and the external iliac plexus. Inferiorly, the superior hypogastric plexus divides into the hypogastric nerves, which descend into the pelvis and contribute to the formation of the inferior hypogastric or pelvic plexus (Fig. 4.137).


Anatomy_Gray

Anatomy_Gray. The abdominal prevertebral plexus receives: preganglionic parasympathetic and visceral afferent fibers from the vagus nerves [X], preganglionic sympathetic and visceral afferent fibers from the thoracic and lumbar splanchnic nerves, and preganglionic parasympathetic fibers from the pelvic splanchnic nerves. Parasympathetic innervation of the abdominal part of the gastrointestinal tract and of the spleen, pancreas, gallbladder, and liver is from two sources—the vagus nerves [X] and the pelvic splanchnic nerves. The vagus nerves [X] enter the abdomen associated with the esophagus as the esophagus passes through the diaphragm (Fig. 4.138) and provide parasympathetic innervation to the foregut and midgut.


Anatomy_Gray

Anatomy_Gray. The vagus nerves [X] enter the abdomen associated with the esophagus as the esophagus passes through the diaphragm (Fig. 4.138) and provide parasympathetic innervation to the foregut and midgut. After entering the abdomen as the anterior and posterior vagal trunks, they send branches to the abdominal prevertebral plexus. These branches contain preganglionic parasympathetic fibers and visceral afferent fibers, which are distributed with the other components of the prevertebral plexus along the branches of the abdominal aorta. The pelvic splanchnic nerves, carrying preganglionic parasympathetic fibers from S2 to S4 spinal cord levels, enter the inferior hypogastric plexus in the pelvis. Some of these fibers move upward into the inferior mesenteric part of the prevertebral plexus in the abdomen (Fig. 4.138). Once there, these fibers are distributed with branches of the inferior mesenteric artery and provide parasympathetic innervation to the hindgut.


Anatomy_Gray

Anatomy_Gray. The enteric system is a division of the visceral part of the nervous system and is a local neuronal circuit in the wall of the gastrointestinal tract. It consists of motor and sensory neurons organized into two interconnected plexuses (the myenteric and submucosal plexuses) between the layers of the gastrointestinal wall, and the associated nerve fibers that pass between the plexuses and from the plexuses to the adjacent tissue (Fig. 4.139). The enteric system regulates and coordinates numerous gastrointestinal tract activities, including gastric secretory activity, gastrointestinal blood flow, and the contraction and relaxation cycles of smooth muscle (peristalsis). Although the enteric system is generally independent of the central nervous system, it does receive input from postganglionic sympathetic and preganglionic parasympathetic neurons that modifies its activities. Sympathetic innervation of the stomach The pathway of sympathetic innervation of the stomach is as follows:


Anatomy_Gray

Anatomy_Gray. Sympathetic innervation of the stomach The pathway of sympathetic innervation of the stomach is as follows: A preganglionic sympathetic fiber originating at the T6 level of the spinal cord enters an anterior root to leave the spinal cord. At the level of the intervertebral foramen, the anterior root (which contains the preganglionic fiber) and a posterior root join to form a spinal nerve. Outside the vertebral column, the preganglionic fiber leaves the anterior ramus of the spinal nerve through the white ramus communicans. The white ramus communicans, containing the preganglionic fiber, connects to the sympathetic trunk. Entering the sympathetic trunk, the preganglionic fiber does not synapse but passes through the trunk and enters the greater splanchnic nerve. The greater splanchnic nerve passes through the crura of the diaphragm and enters the celiac ganglion. In the celiac ganglion, the preganglionic fiber synapses with a postganglionic neuron.


Anatomy_Gray

Anatomy_Gray. The greater splanchnic nerve passes through the crura of the diaphragm and enters the celiac ganglion. In the celiac ganglion, the preganglionic fiber synapses with a postganglionic neuron. The postganglionic fiber joins the plexus of nerve fibers surrounding the celiac trunk and continues along its branches. The postganglionic fiber travels through the plexus of nerves accompanying the branches of the celiac trunk supplying the stomach and eventually reaches its point of distribution. This input from the sympathetic system may modify the activities of the gastrointestinal tract controlled by the enteric nervous system.


Anatomy_Gray

Anatomy_Gray. This input from the sympathetic system may modify the activities of the gastrointestinal tract controlled by the enteric nervous system. The posterior abdominal region is posterior to the abdominal part of the gastrointestinal tract, the spleen, and the pancreas (Fig. 4.140). This area, bounded by bones and muscles making up the posterior abdominal wall, contains numerous structures that not only are directly involved in the activities of the abdominal contents but also use this area as a conduit between body regions. Examples include the abdominal aorta and its associated nerve plexuses, the inferior vena cava, the sympathetic trunks, and lymphatics. There are also structures originating in this area that are critical to the normal function of other regions of the body (i.e., the lumbar plexus of nerves), and there are organs that associate with this area during development and remain in it in the adult (i.e., the kidneys and suprarenal glands). Lumbar vertebrae and the sacrum


Anatomy_Gray

Anatomy_Gray. Lumbar vertebrae and the sacrum Projecting into the midline of the posterior abdominal area are the bodies of the five lumbar vertebrae (Fig. 4.141). The prominence of these structures in this region is due to the secondary curvature (a forward convexity) of the lumbar part of the vertebral column. The lumbar vertebrae can be distinguished from cervical and thoracic vertebrae because of their size. They are much larger than any other vertebrae in any other region. The vertebral bodies are massive and progressively increase in size from vertebra LI to LV. The pedicles are short and stocky, the transverse processes are long and slender, and the spinous processes are large and stubby. The articular processes are large and oriented medially and laterally, which promotes flexion and extension in this part of the vertebral column. Between each lumbar vertebra is an intervertebral disc, which completes this part of the midline boundary of the posterior abdominal wall.


Anatomy_Gray

Anatomy_Gray. Between each lumbar vertebra is an intervertebral disc, which completes this part of the midline boundary of the posterior abdominal wall. The midline boundary of the posterior abdominal wall, inferior to the lumbar vertebrae, consists of the upper margin of the sacrum (Fig. 4.141). The sacrum is formed by the fusion of the five sacral vertebrae into a single, wedge-shaped bony structure that is broad superiorly and narrows inferiorly. Its concave anterior surface and its convex posterior surface contain anterior and posterior sacral foramina for the anterior and posterior rami of spinal nerves to pass through. The ilia, which are components of each pelvic bone, attach laterally to the sacrum at the sacro-iliac joints (Fig. 4.141). The upper part of each ilium expands outward into a thin wing-like area (the iliac fossa). The medial side of this region of each iliac bone, and the related muscles, are components of the posterior abdominal wall.


Anatomy_Gray

Anatomy_Gray. Superiorly, ribs XI and XII complete the bony framework of the posterior abdominal wall (Fig. 4.141). These ribs are unique in that they do not articulate with the sternum or other ribs, they have a single articular facet on their heads, and they do not have necks or tubercles. Rib XI is posterior to the superior part of the left kidney, and rib XII is posterior to the superior part of both kidneys. Also, rib XII serves as a point of attachment for numerous muscles and ligaments. Muscles forming the medial, lateral, inferior, and superior boundaries of the posterior abdominal region fill in the bony framework of the posterior abdominal wall (Table 4.2). Medially are the psoas major and minor muscles, laterally is the quadratus lumborum muscle, inferiorly is the iliacus muscle, and superiorly is the diaphragm (Figs. 4.142 and 4.143).


Anatomy_Gray

Anatomy_Gray. Medially, the psoas major muscles cover the anterolateral surface of the bodies of the lumbar vertebrae, filling in the space between the vertebral bodies and the transverse processes (Fig. 4.142). Each of these muscles arises from the bodies of vertebra TXII and all five lumbar vertebrae, from the intervertebral discs between each vertebra, and from the transverse processes of the lumbar vertebrae. Passing inferiorly along the pelvic brim, each muscle continues into the anterior thigh, under the inguinal ligament, to attach to the lesser trochanter of the femur. The psoas major muscle flexes the thigh at the hip joint when the trunk is stabilized and flexes the trunk against gravity when the body is supine. It is innervated by anterior rami of nerves L1 to L3.


Anatomy_Gray

Anatomy_Gray. Associated with the psoas major muscle is the psoas minor muscle, which is sometimes absent. Lying on the surface of the psoas major when present, this slender muscle arises from vertebrae TXII and LI and the intervening intervertebral disc; its long tendon inserts into the pectineal line of the pelvic brim and the iliopubic eminence. The psoas minor is a weak flexor of the lumbar vertebral column and is innervated by the anterior ramus of nerve L1. Laterally, the quadratus lumborum muscles fill the space between rib XII and the iliac crest on both sides of the vertebral column (Fig. 4.142). They are overlapped medially by the psoas major muscles; along their lateral borders are the transversus abdominis muscles.


Anatomy_Gray

Anatomy_Gray. Each quadratus lumborum muscle arises from the transverse process of vertebra LV, the iliolumbar ligament, and the adjoining part of the iliac crest. The muscle attaches superiorly to the transverse process of the first four lumbar vertebrae and the inferior border of rib XII. The quadratus lumborum muscles depress and stabilize the twelfth ribs and contribute to lateral bending of the trunk. Acting together, the muscles may extend the lumbar part of the vertebral column. They are innervated by anterior rami of T12 and L1 to L4 spinal nerves. Inferiorly, an iliacus muscle fills the iliac fossa on each side (Fig. 4.142). From this expansive origin covering the iliac fossa, the muscle passes inferiorly, joins with the psoas major muscle, and attaches to the lesser trochanter of the femur. As they pass into the thigh, these combined muscles are referred to as the iliopsoas muscle.


Anatomy_Gray

Anatomy_Gray. Like the psoas major muscle, the iliacus flexes the thigh at the hip joint when the trunk is stabilized and flexes the trunk against gravity when the body is supine. It is innervated by branches of the femoral nerve. Superiorly, the diaphragm forms the boundary of the posterior abdominal region. This musculotendinous sheet also separates the abdominal cavity from the thoracic cavity. Structurally, the diaphragm consists of a central tendinous part into which the circumferentially arranged muscle fibers attach (Fig. 4.143). The diaphragm is anchored to the lumbar vertebrae by musculotendinous crura, which blend with the anterior longitudinal ligament of the vertebral column: The right crus is the longest and broadest of the crura and is attached to the bodies of vertebrae LI to LIII and the intervening intervertebral discs (Fig. 4.144). Similarly, the left crus is attached to vertebrae LI and LII and the associated intervertebral disc.


Anatomy_Gray

Anatomy_Gray. Similarly, the left crus is attached to vertebrae LI and LII and the associated intervertebral disc. The crura are connected across the midline by a tendinous arch (the median arcuate ligament), which passes anterior to the aorta (Fig. 4.144). Lateral to the crura, a second tendinous arch is formed by the fascia covering the upper part of the psoas major muscle. This is the medial arcuate ligament, which is attached medially to the sides of vertebrae LI and LII and laterally to the transverse process of vertebra LI (Fig. 4.144). A third tendinous arch, the lateral arcuate ligament, is formed by a thickening in the fascia that covers the quadratus lumborum. It is attached medially to the transverse process of vertebra LI and laterally to rib XII (Fig. 4.144). The medial and lateral arcuate ligaments serve as points of origin for some of the muscular components of the diaphragm. Structures passing through or around the diaphragm


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Anatomy_Gray. The medial and lateral arcuate ligaments serve as points of origin for some of the muscular components of the diaphragm. Structures passing through or around the diaphragm Numerous structures pass through or around the diaphragm (Fig. 4.143): The aorta passes posterior to the diaphragm and anterior to the vertebral bodies at the lower level of vertebra TXII; it is between the two crura of the diaphragm and posterior to the median arcuate ligament, just to the left of midline. Accompanying the aorta through the aortic hiatus is the thoracic duct and, sometimes, the azygos vein. The esophagus passes through the musculature of the right crus of the diaphragm at the level of vertebra TX, just to the left of the aortic hiatus. Passing through the esophageal hiatus with the esophagus are the anterior and posterior vagal trunks, the esophageal branches of the left gastric artery and vein, and a few lymphatic vessels.


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Anatomy_Gray. Passing through the esophageal hiatus with the esophagus are the anterior and posterior vagal trunks, the esophageal branches of the left gastric artery and vein, and a few lymphatic vessels. The third large opening in the diaphragm is the caval opening, through which the inferior vena cava passes from the abdominal cavity to the thoracic cavity (Fig. 4.143) at approximately vertebra TVIII in the central tendinous part of the diaphragm. Accompanying the inferior vena cava through the caval opening is the right phrenic nerve. The left phrenic nerve passes through the muscular part of the diaphragm just anterior to the central tendon on the left side. Additional structures pass through small openings either in or just outside the diaphragm as they pass from the thoracic cavity to the abdominal cavity (Fig. 4.143): The greater, lesser, and least (when present) splanchnic nerves pass through the crura, on either side. The hemi-azygos vein passes through the left crus.


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Anatomy_Gray. The greater, lesser, and least (when present) splanchnic nerves pass through the crura, on either side. The hemi-azygos vein passes through the left crus. Passing posterior to the medial arcuate ligament, on either side, are the sympathetic trunks. Passing anterior to the diaphragm, just deep to the ribs, are the superior epigastric vessels. Other vessels and nerves (i.e., the musculophrenic vessels and intercostal nerves) also pass through the diaphragm at various points. The classic appearance of the right and left domes of the diaphragm is caused by the underlying abdominal contents pushing these lateral areas upward, and by the fibrous pericardium, which is attached centrally, causing a flattening of the diaphragm in this area (Fig. 4.145).


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Anatomy_Gray. The domes are produced by: the liver on the right, with some contribution from the right kidney and the right suprarenal gland, and the fundus of the stomach and spleen on the left, with contributions from the left kidney and the left suprarenal gland. Although the height of these domes varies during breathing, a reasonable estimate in normal expiration places the left dome at the fifth intercostal space and the right dome at rib V. This is important to remember when percussing the thorax. During inspiration, the muscular part of the diaphragm contracts, causing the central tendon of the diaphragm to be drawn inferiorly. This results in some flattening of the domes, enlargement of the thoracic cavity, and a reduction in intrathoracic pressure. The physiological effect of these changes is that air enters the lungs and venous return to the heart is enhanced. There is blood supply to the diaphragm on its superior and inferior surfaces:


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Anatomy_Gray. There is blood supply to the diaphragm on its superior and inferior surfaces: Superiorly, the musculophrenic and pericardiacophrenic arteries, both branches of the internal thoracic artery, and the superior phrenic artery, a branch of the thoracic aorta, supply the diaphragm. Inferiorly, the inferior phrenic arteries, branches of the abdominal aorta, supply the diaphragm (see Fig. 4.143). Venous drainage is through companion veins to these arteries. Innervation of the diaphragm is primarily by the phrenic nerves. These nerves, from the C3 to C5 spinal cord levels, provide all motor innervation to the diaphragm and sensory fibers to the central part. They pass through the thoracic cavity, between the mediastinal pleura and the pericardium, to the superior surface of the diaphragm. At this point, the right phrenic nerve accompanies the inferior vena cava through the diaphragm and the left phrenic nerve passes through the diaphragm by itself (see


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Anatomy_Gray. Fig. 4.143). Additional sensory fibers are supplied to the peripheral areas of the diaphragm by intercostal nerves. The bean-shaped kidneys are retroperitoneal in the posterior abdominal region (Fig. 4.149). They lie in the extraperitoneal connective tissue immediately lateral to the vertebral column. In the supine position, the kidneys extend from approximately vertebra TXII superiorly to vertebra LIII inferiorly, with the right kidney somewhat lower than the left because of its relationship with the liver. Although they are similar in size and shape, the left kidney is a longer and more slender organ than the right kidney, and nearer to the midline. Relationships to other structures The anterior surface of the right kidney is related to numerous structures, some of which are separated from the kidney by a layer of peritoneum and some of which are directly against the kidney (Fig. 4.150): A small part of the superior pole is covered by the right suprarenal gland.


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Anatomy_Gray. A small part of the superior pole is covered by the right suprarenal gland. Moving inferiorly, a large part of the rest of the upper part of the anterior surface is against the liver and is separated from it by a layer of peritoneum. Medially, the descending part of the duodenum is retroperitoneal and contacts the kidney. The inferior pole of the kidney, on its lateral side, is directly associated with the right colic flexure and, on its medial side, is covered by a segment of the intraperitoneal small intestine. The anterior surface of the left kidney is also related to numerous structures, some with an intervening layer of peritoneum and some directly against the kidney (Fig. 4.150): A small part of the superior pole, on its medial side, is covered by the left suprarenal gland. The rest of the superior pole is covered by the intraperitoneal stomach and spleen. Moving inferiorly, the retroperitoneal pancreas covers the middle part of the kidney.


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Anatomy_Gray. The rest of the superior pole is covered by the intraperitoneal stomach and spleen. Moving inferiorly, the retroperitoneal pancreas covers the middle part of the kidney. On its lateral side, the lower half of the kidney is covered by the left colic flexure and the beginning of the descending colon, and, on its medial side, by the parts of the intraperitoneal jejunum. Posteriorly, the right and left kidneys are related to similar structures (Fig. 4.151). Superiorly is the diaphragm and inferior to this, moving in a medial to lateral direction, are the psoas major, quadratus lumborum, and transversus abdominis muscles. The superior pole of the right kidney is anterior to rib XII, while the same region of the left kidney is anterior to ribs XI and XII. The pleural sacs and specifically the costodiaphragmatic recesses therefore extend posterior to the kidneys. Also passing posterior to the kidneys are the subcostal vessels and nerves and the iliohypogastric and ilio-inguinal nerves.


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Anatomy_Gray. Also passing posterior to the kidneys are the subcostal vessels and nerves and the iliohypogastric and ilio-inguinal nerves. The kidneys are enclosed in and associated with a unique arrangement of fascia and fat. Immediately outside the renal capsule, there is an accumulation of extraperitoneal fat—the perinephric fat (perirenal fat), which completely surrounds the kidney (Fig. 4.152). Enclosing the perinephric fat is a membranous condensation of the extraperitoneal fascia (the renal fascia). The suprarenal glands are also enclosed in this fascial compartment, usually separated from the kidneys by a thin septum. The renal fascia must be incised in any surgical approach to this organ. At the lateral margins of each kidney, the anterior and posterior layers of the renal fascia fuse (Fig. 4.152). This fused layer may connect with the transversalis fascia on the lateral abdominal wall.


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Anatomy_Gray. Above each suprarenal gland, the anterior and posterior layers of the renal fascia fuse and blend with the fascia that covers the diaphragm. Medially, the anterior layer of the renal fascia continues over the vessels in the hilum and fuses with the connective tissue associated with the abdominal aorta and the inferior vena cava (Fig. 4.152). In some cases, the anterior layer may cross the midline to the opposite side and blend with its companion layer. The posterior layer of the renal fascia passes medially between the kidney and the fascia covering the quadratus lumborum muscle to fuse with the fascia covering the psoas major muscle. Inferiorly, the anterior and posterior layers of the renal fascia enclose the ureters. In addition to perinephric fat and the renal fascia, a final layer of paranephric fat (pararenal fat) completes the fat and fascias associated with the kidney (Fig. 4.152). This fat accumulates posterior and posterolateral to each kidney.


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Anatomy_Gray. Each kidney has a smooth anterior and posterior surface covered by a fibrous capsule, which is easily removable except during disease. On the medial margin of each kidney is the hilum of the kidney, which is a deep vertical slit through which renal vessels, lymphatics, and nerves enter and leave the substance of the kidney (Fig. 4.153). Internally, the hilum is continuous with the renal sinus. Perinephric fat continues into the hilum and sinus and surrounds all structures. Each kidney consists of an outer renal cortex and an inner renal medulla. The renal cortex is a continuous band of pale tissue that completely surrounds the renal medulla. Extensions of the renal cortex (the renal columns) project into the inner aspect of the kidney, dividing the renal medulla into discontinuous aggregations of triangular-shaped tissue (the renal pyramids).


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Anatomy_Gray. The bases of the renal pyramids are directed outward, toward the renal cortex, while the apex of each renal pyramid projects inward, toward the renal sinus. The apical projection (renal papilla) contains the openings of the papillary ducts draining the renal tubules and is surrounded by a minor calyx. The minor calices receive urine from the papillary ducts and represent the proximal parts of the tube that will eventually form the ureter (Fig. 4.153). In the renal sinus, several minor calices unite to form a major calyx, and two or three major calices unite to form the renal pelvis, which is the funnel-shaped superior end of the ureters.


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Anatomy_Gray. A single large renal artery, a lateral branch of the abdominal aorta, supplies each kidney. These vessels usually arise just inferior to the origin of the superior mesenteric artery between vertebrae LI and LII (Fig. 4.154). The left renal artery usually arises a little higher than the right, and the right renal artery is longer and passes posterior to the inferior vena cava. As each renal artery approaches the renal hilum, it divides into anterior and posterior branches, which supply the renal parenchyma. Accessory renal arteries are common. They originate from the lateral aspect of the abdominal aorta, either above or below the primary renal arteries, enter the hilum with the primary arteries or pass directly into the kidney at some other level, and are commonly called extrahilar arteries.


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Anatomy_Gray. Multiple renal veins contribute to the formation of the left and right renal veins, both of which are anterior to the renal arteries (Fig. 4.154A). Importantly, the longer left renal vein crosses the midline anterior to the abdominal aorta and posterior to the superior mesenteric artery and can be compressed by an aneurysm in either of these two vessels (Fig. 4.154B). The lymphatic drainage of each kidney is to the lateral aortic (lumbar) nodes around the origin of the renal artery. The ureters are muscular tubes that transport urine from the kidneys to the bladder. They are continuous superiorly with the renal pelvis, which is a funnel-shaped structure in the renal sinus. The renal pelvis is formed from a condensation of two or three major calices, which in turn are formed by the condensation of several minor calices (see Fig. 4.153). The minor calices surround a renal papilla.


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Anatomy_Gray. The renal pelvis narrows as it passes inferiorly through the hilum of the kidney and becomes continuous with the ureter at the ureteropelvic junction (Fig. 4.155). Inferior to this junction, the ureters descend retroperitoneally on the medial aspect of the psoas major muscle. At the pelvic brim, the ureters cross either the end of the common iliac artery or the beginning of the external iliac artery, enter the pelvic cavity, and continue their journey to the bladder. At three points along their course the ureters are constricted (Fig. 4.155): The first point is at the ureteropelvic junction. The second point is where the ureters cross the common iliac vessels at the pelvic brim. The third point is where the ureters enter the wall of the bladder. Kidney stones can become lodged at these constrictions. The ureters receive arterial branches from adjacent vessels as they pass toward the bladder (Fig. 4.155): The renal arteries supply the upper end.


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Anatomy_Gray. The ureters receive arterial branches from adjacent vessels as they pass toward the bladder (Fig. 4.155): The renal arteries supply the upper end. The middle part may receive branches from the abdominal aorta, the testicular or ovarian arteries, and the common iliac arteries. In the pelvic cavity, the ureters are supplied by one or more arteries from branches of the internal iliac arteries. In all cases, arteries reaching the ureters divide into ascending and descending branches, which form longitudinal anastomoses. Lymphatic drainage of the ureters follows a pattern similar to that of the arterial supply. Lymph from: the upper part of each ureter drains to the lateral aortic (lumbar) nodes, the middle part of each ureter drains to lymph nodes associated with the common iliac vessels, and the inferior part of each ureter drains to lymph nodes associated with the external and internal iliac vessels.


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Anatomy_Gray. Ureteric innervation is from the renal, aortic, superior hypogastric, and inferior hypogastric plexuses through nerves that follow the blood vessels. Visceral efferent fibers come from both sympathetic and parasympathetic sources, whereas visceral afferent fibers return to T11 to L2 spinal cord levels. Ureteric pain, which is usually related to distention of the ureter, is therefore referred to cutaneous areas supplied by T11 to L2 spinal cord levels. These areas would most likely include the posterior and lateral abdominal wall below the ribs and above the iliac crest, the pubic region, the scrotum in males, the labia majora in females, and the proximal anterior aspect of the thigh. The suprarenal glands are associated with the superior pole of each kidney (Fig. 4.163). They consist of an outer cortex and an inner medulla. The right gland is shaped like a pyramid, whereas the left gland is semilunar in shape and the larger of the two.


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Anatomy_Gray. Anterior to the right suprarenal gland is part of the right lobe of the liver and the inferior vena cava, whereas anterior to the left suprarenal gland is part of the stomach, pancreas, and, on occasion, the spleen. Parts of the diaphragm are posterior to both glands. The suprarenal glands are surrounded by the perinephric fat and enclosed in the renal fascia, though a thin septum separates each gland from its associated kidney. The arterial supply to the suprarenal glands is extensive and arises from three primary sources (Fig. 4.163): As the bilateral inferior phrenic arteries pass upward from the abdominal aorta to the diaphragm, they give off multiple branches (superior suprarenal arteries) to the suprarenal glands. A middle branch (middle suprarenal artery) to the suprarenal glands usually arises directly from the abdominal aorta. Inferior branches (inferior suprarenal arteries) from the renal arteries pass upward to the suprarenal glands.


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Anatomy_Gray. Inferior branches (inferior suprarenal arteries) from the renal arteries pass upward to the suprarenal glands. In contrast to this multiple arterial supply is the venous drainage, which usually consists of a single vein leaving the hilum of each gland. On the right side, the right suprarenal vein is short and almost immediately enters the inferior vena cava, while on the left side, the left suprarenal vein passes inferiorly to enter the left renal vein. The suprarenal gland is mainly innervated by preganglionic sympathetic fibers from spinal levels T8-L1 that pass through both the sympathetic trunk and the prevertebral plexus without synapsing. These preganglionic fibers directly innervate cells of the adrenal medulla.


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Anatomy_Gray. The abdominal aorta begins at the aortic hiatus of the diaphragm as a midline structure at approximately the lower level of vertebra TXII (Fig. 4.164). It passes downward on the anterior surface of the bodies of vertebrae LI to LIV, ending just to the left of midline at the lower level of vertebra LIV. At this point, it divides into the right and left common iliac arteries. This bifurcation can be visualized on the anterior abdominal wall as a point approximately 2.5 cm below the umbilicus or even with a line extending between the highest points of the iliac crest. As the abdominal aorta passes through the posterior abdominal region, the prevertebral plexus of nerves and ganglia covers its anterior surface. It is also related to numerous other structures: Anterior to the abdominal aorta, as it descends, are the pancreas and splenic vein, the left renal vein, and the inferior part of the duodenum.


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Anatomy_Gray. Anterior to the abdominal aorta, as it descends, are the pancreas and splenic vein, the left renal vein, and the inferior part of the duodenum. Several left lumbar veins cross it posteriorly as they pass to the inferior vena cava. On its right side are the cisterna chyli, thoracic duct, azygos vein, right crus of the diaphragm, and the inferior vena cava. On its left side is the left crus of the diaphragm. Branches of the abdominal aorta (Table 4.3) can be classified as: visceral branches supplying organs, posterior branches supplying the diaphragm or body wall, or terminal branches. The visceral branches are either unpaired or paired vessels. The three unpaired visceral branches that arise from the anterior surface of the abdominal aorta (Fig. 4.164) are: the celiac trunk, which supplies the abdominal foregut, the superior mesenteric artery, which supplies the abdominal midgut, and the inferior mesenteric artery, which supplies the abdominal hindgut.


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Anatomy_Gray. The paired visceral branches of the abdominal aorta (Fig. 4.164) include: the middle suprarenal arteries—small, lateral branches of the abdominal aorta arising just above the renal arteries that are part of the multiple vascular supply to the suprarenal gland; the renal arteries—lateral branches of the abdominal aorta that arise just inferior to the origin of the superior mesenteric artery between vertebrae LI and LII, and supply the kidneys; and the testicular or ovarian arteries—anterior branches of the abdominal aorta that arise below the origin of the renal arteries, and pass downward and laterally on the anterior surface of the psoas major muscle. The posterior branches of the abdominal aorta are vessels supplying the diaphragm or body wall. They consist of the inferior phrenic arteries, the lumbar arteries, and the median sacral artery (Fig. 4.164).


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Anatomy_Gray. The inferior phrenic arteries arise immediately inferior to the aortic hiatus of the diaphragm either directly from the abdominal aorta, as a common trunk from the abdominal aorta, or from the base of the celiac trunk (Fig. 4.164). Whatever their origin, they pass upward, provide some arterial supply to the suprarenal gland, and continue onto the inferior surface of the diaphragm. There are usually four pairs of lumbar arteries arising from the posterior surface of the abdominal aorta (Fig. 4.164). They run laterally and posteriorly over the bodies of the lumbar vertebrae, continue laterally, passing posterior to the sympathetic trunks and between the transverse processes of adjacent lumbar vertebrae, and reach the abdominal wall. From this point onward, they demonstrate a branching pattern similar to a posterior intercostal artery, which includes providing segmental branches that supply the spinal cord.


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Anatomy_Gray. The final posterior branch is the median sacral artery (Fig. 4.164). This vessel arises from the posterior surface of the abdominal aorta just superior to the bifurcation and passes in an inferior direction, first over the anterior surface of the lower lumbar vertebrae and then over the anterior surface of the sacrum and coccyx. The inferior vena cava returns blood from all structures below the diaphragm to the right atrium of the heart. It is formed when the two common iliac veins come together at the level of vertebra LV, just to the right of midline. It ascends through the posterior abdominal region anterior to the vertebral column immediately to the right of the abdominal aorta (Fig. 4.166), continues in a superior direction, and leaves the abdomen by piercing the central tendon of the diaphragm at the level of vertebra TVIII.


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Anatomy_Gray. During its course, the anterior surface of the inferior vena cava is crossed by the right common iliac artery, the root of the mesentery, the right testicular or ovarian artery, the inferior part of the duodenum, the head of the pancreas, the superior part of the duodenum, the bile duct, the portal vein, and the liver, which overlaps and on occasion completely surrounds the vena cava (Fig. 4.166). Tributaries to the inferior vena cava include the: common iliac veins, lumbar veins, right testicular or ovarian vein, renal veins, right suprarenal vein, inferior phrenic veins, and hepatic veins. There are no tributaries from the abdominal part of the gastrointestinal tract, the spleen, the pancreas, or the gallbladder, because veins from these structures are components of the portal venous system, which first passes through the liver.


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Anatomy_Gray. Of the venous tributaries mentioned above, the lumbar veins are unique in their connections and deserve special attention. Not all of the lumbar veins drain directly into the inferior vena cava (Fig. 4.167): The fifth lumbar vein generally drains into the iliolumbar vein, a tributary of the common iliac vein. The third and fourth lumbar veins usually drain into the inferior vena cava. The first and second lumbar veins may empty into the ascending lumbar veins. The ascending lumbar veins are long, anastomosing venous channels that connect the common iliac, iliolumbar, and lumbar veins with the azygos and hemi-azygos veins of the thorax (Fig. 4.167). If the inferior vena cava becomes blocked, the ascending lumbar veins become important collateral channels between the lower and upper parts of the body.


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Anatomy_Gray. If the inferior vena cava becomes blocked, the ascending lumbar veins become important collateral channels between the lower and upper parts of the body. Lymphatic drainage from most deep structures and regions of the body below the diaphragm converges mainly on collections of lymph nodes and vessels associated with the major blood vessels of the posterior abdominal region (Fig. 4.168). The lymph then predominantly drains into the thoracic duct. Major lymphatic channels that drain different regions of the body as a whole are summarized in Table 4.4 (also see Chapter 1, pp. 27–28, for discussion of lymphatics in general).


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Anatomy_Gray. Table 4.4 (also see Chapter 1, pp. 27–28, for discussion of lymphatics in general). Approaching the aortic bifurcation, the collections of lymphatics associated with the two common iliac arteries and veins merge, and multiple groups of lymphatic vessels and nodes associated with the abdominal aorta and inferior vena cava pass superiorly. These collections may be subdivided into pre-aortic nodes, which are anterior to the abdominal aorta, and right and left lateral aortic or lumbar nodes (para-aortic nodes), which are positioned on either side of the abdominal aorta (Fig. 4.168). As these collections of lymphatics pass through the posterior abdominal region, they continue to collect lymph from a variety of structures. The lateral aortic or lumbar lymph nodes (para-aortic nodes) receive lymphatics from the body wall, the kidneys, the suprarenal glands, and the testes or ovaries.


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Anatomy_Gray. The pre-aortic nodes are organized around the three anterior branches of the abdominal aorta that supply the abdominal part of the gastrointestinal tract, as well as the spleen, pancreas, gallbladder, and liver. They are divided into celiac, superior mesenteric, and inferior mesenteric nodes, and receive lymph from the organs supplied by the similarly named arteries. Finally, the lateral aortic or lumbar nodes form the right and left lumbar trunks, whereas the pre-aortic nodes form the intestinal trunk (Fig. 4.168). These trunks come together and form a confluence that, at times, appears as a saccular dilation (the cisterna chyli). This confluence of lymph trunks is posterior to the right side of the abdominal aorta and anterior to the bodies of vertebrae LI and LII. It marks the beginning of the thoracic duct. Nervous system in the posterior


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Anatomy_Gray. Nervous system in the posterior Several important components of the nervous system are in the posterior abdominal region. These include the sympathetic trunks and associated splanchnic nerves, the plexus of nerves and ganglia associated with the abdominal aorta, and the lumbar plexus of nerves. The sympathetic trunks pass through the posterior abdominal region anterolateral to the lumbar vertebral bodies, before continuing across the sacral promontory and into the pelvic cavity (Fig. 4.169). Along their course, small raised areas are visible. These represent collections of neuronal cell bodies—primarily postganglionic neuronal cell bodies—which are located outside the central nervous system. They are sympathetic paravertebral ganglia. There are usually four ganglia along the sympathetic trunks in the posterior abdominal region.


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Anatomy_Gray. Also associated with the sympathetic trunks in the posterior abdominal region are the lumbar splanchnic nerves (Fig. 4.169). These components of the nervous system pass from the sympathetic trunks to the plexus of nerves and ganglia associated with the abdominal aorta. Usually two to four lumbar splanchnic nerves carry preganglionic sympathetic fibers and visceral afferent fibers. The abdominal prevertebral plexus is a network of nerve fibers surrounding the abdominal aorta. It extends from the aortic hiatus of the diaphragm to the bifurcation of the aorta into the right and left common iliac arteries. Along its route, it is subdivided into smaller, named plexuses (Fig. 4.170): Beginning at the diaphragm and moving inferiorly, the initial accumulation of nerve fibers is referred to as the celiac plexus—this subdivision includes nerve fibers associated with the roots of the celiac trunk and superior mesenteric artery.


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Anatomy_Gray. Continuing inferiorly, the plexus of nerve fibers extending from just below the superior mesenteric artery to the aortic bifurcation is the abdominal aortic plexus (Fig. 4.170). At the bifurcation of the abdominal aorta, the abdominal prevertebral plexus continues inferiorly as the superior hypogastric plexus. Throughout its length, the abdominal prevertebral plexus is a conduit for: preganglionic sympathetic and visceral afferent fibers from the thoracic and lumbar splanchnic nerves, preganglionic parasympathetic and visceral afferent fibers from the vagus nerves [X], and preganglionic parasympathetic fibers from the pelvic splanchnic nerves (Fig. 4.171).


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Anatomy_Gray. Associated with the abdominal prevertebral plexus are clumps of nervous tissue (the prevertebral ganglia), which are collections of postganglionic sympathetic neuronal cell bodies in recognizable aggregations along the abdominal prevertebral plexus; they are usually named after the nearest branch of the abdominal aorta. They are therefore referred to as celiac, superior mesenteric, aorticorenal, and inferior mesenteric ganglia (Fig. 4.172). These structures, along with the abdominal prevertebral plexus, play a critical role in the innervation of the abdominal viscera. Common sites for pain referred from the abdominal viscera and from the heart are given in Table 4.5. The lumbar plexus is formed by the anterior rami of nerves L1 to L3 and most of the anterior ramus of L4 (Fig. 4.173 and Table 4.6). It also receives a contribution from the T12 (subcostal) nerve.


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Anatomy_Gray. The lumbar plexus is formed by the anterior rami of nerves L1 to L3 and most of the anterior ramus of L4 (Fig. 4.173 and Table 4.6). It also receives a contribution from the T12 (subcostal) nerve. Branches of the lumbar plexus include the iliohypogastric, ilio-inguinal, and genitofemoral nerves, the lateral cutaneous nerve of the thigh (lateral femoral cutaneous), and femoral and obturator nerves. The lumbar plexus forms in the substance of the psoas major muscle anterior to its attachment to the transverse processes of the lumbar vertebrae (Fig. 4.174). Therefore, relative to the psoas major muscle, the various branches emerge either: anterior—genitofemoral nerve, medial—obturator nerve, or lateral—iliohypogastric, ilio-inguinal, and femoral nerves and the lateral cutaneous nerve of the thigh.


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Anatomy_Gray. The iliohypogastric and ilio-inguinal nerves arise as a single trunk from the anterior ramus of nerve L1 (Fig. 4.173). Either before or soon after emerging from the lateral border of the psoas major muscle, this single trunk divides into the iliohypogastric and the ilio-inguinal nerves. The iliohypogastric nerve passes across the anterior surface of the quadratus lumborum muscle, posterior to the kidney. It pierces the transversus abdominis muscle and continues anteriorly around the body between the transversus abdominis and internal oblique muscles. Above the iliac crest, a lateral cutaneous branch pierces the internal and external oblique muscles to supply the posterolateral gluteal skin (Fig. 4.175).


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Anatomy_Gray. The remaining part of the iliohypogastric nerve (the anterior cutaneous branch) continues in an anterior direction, piercing the internal oblique just medial to the anterior superior iliac spine as it continues in an obliquely downward and medial direction. Becoming cutaneous, just above the superficial inguinal ring, after piercing the aponeurosis of the external oblique, it distributes to the skin in the pubic region (Fig. 4.175). Throughout its course, it also supplies branches to the abdominal musculature. The ilio-inguinal nerve is smaller than, and inferior to, the iliohypogastric nerve as it crosses the quadratus lumborum muscle. Its course is more oblique than that of the iliohypogastric nerve, and it usually crosses part of the iliacus muscle on its way to the iliac crest. Near the anterior end of the iliac crest, it pierces the transversus abdominis muscle, and then pierces the internal oblique muscle and enters the inguinal canal.


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Anatomy_Gray. The ilio-inguinal nerve emerges through the superficial inguinal ring, along with the spermatic cord, and provides cutaneous innervation to the upper medial thigh, the root of the penis, and the anterior surface of the scrotum in men, or the mons pubis and labium majus in women (Fig. 4.175). Throughout its course, it also supplies branches to the abdominal musculature. The genitofemoral nerve arises from the anterior rami of nerves L1 and L2 (Fig. 4.173). It passes downward in the substance of the psoas major muscle until it emerges on the anterior surface of the psoas major. It then descends on the surface of the muscle, in a retroperitoneal position, passing posterior to the ureter. It eventually divides into genital and femoral branches.


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Anatomy_Gray. The genital branch continues downward and enters the inguinal canal through the deep inguinal ring. It continues through the canal and: in men, innervates the cremasteric muscle and terminates on the skin in the upper anterior part of the scrotum, and in women, accompanies the round ligament of the uterus and terminates on the skin of the mons pubis and labium majus. The femoral branch descends on the lateral side of the external iliac artery and passes posterior to the inguinal ligament, entering the femoral sheath lateral to the femoral artery. It pierces the anterior layer of the femoral sheath and the fascia lata to supply the skin of the upper anterior thigh (Fig. 4.175). Lateral cutaneous nerve of thigh (L2 and L3)


Anatomy_Gray

Anatomy_Gray. Lateral cutaneous nerve of thigh (L2 and L3) The lateral cutaneous nerve of the thigh arises from the anterior rami of nerves L2 and L3 (Fig. 4.173). It emerges from the lateral border of the psoas major muscle, passing obliquely downward across the iliacus muscle toward the anterior superior iliac spine (Fig. 4.175). It passes posterior to the inguinal ligament and enters the thigh. The lateral cutaneous nerve of the thigh supplies the skin on the anterior and lateral thigh to the level of the knee (Fig. 4.175). Obturator nerve (L2 to L4) The obturator nerve arises from the anterior rami of nerves L2 to L4 (Fig. 4.173). It descends in the psoas major muscle, emerging from its medial side near the pelvic brim (Fig. 4.174). The obturator nerve continues posterior to the common iliac vessels, passes across the lateral wall of the pelvic cavity, and enters the obturator canal, through which the obturator nerve gains access to the medial compartment of the thigh.


Anatomy_Gray

Anatomy_Gray. In the area of the obturator canal, the obturator nerve divides into anterior and posterior branches. On entering the medial compartment of the thigh, the two branches are separated by the obturator externus and adductor brevis muscles. Throughout their course through the medial compartment, these two branches supply: articular branches to the hip joint, muscular branches to the obturator externus, pectineus, adductor longus, gracilis, adductor brevis, and adductor magnus muscles, cutaneous branches to the medial aspect of the thigh, and in association with the saphenous nerve, cutaneous branches to the medial aspect of the upper part of the leg and articular branches to the knee joint (Fig. 4.175). Femoral nerve (L2 to L4)


Anatomy_Gray

Anatomy_Gray. Femoral nerve (L2 to L4) The femoral nerve arises from the anterior rami of nerves L2 to L4 (Fig. 4.173). It descends through the substance of the psoas major muscle, emerging from the lower lateral border of the psoas major (Fig. 4.174). Continuing its descent, the femoral nerve lies between the lateral border of the psoas major and the anterior surface of the iliacus muscle. It is deep to the iliacus fascia and lateral to the femoral artery as it passes posterior to the inguinal ligament and enters the anterior compartment of the thigh. Upon entering the thigh, it immediately divides into multiple branches. Cutaneous branches of the femoral nerve include: medial and intermediate cutaneous nerves supplying the skin on the anterior surface of the thigh, and the saphenous nerve supplying the skin on the medial surface of the leg (Fig. 4.175).


Anatomy_Gray

Anatomy_Gray. Muscular branches innervate the iliacus, pectineus, sartorius, rectus femoris, vastus medialis, vastus intermedius, and vastus lateralis muscles. Articular branches supply the hip and knee joints. Visualization of the position of abdominal viscera is fundamental to a physical examination. Some of these viscera or their parts can be felt by palpating through the abdominal wall. Surface features can be used to establish the positions of deep structures. Defining the surface projection of the abdomen Palpable landmarks can be used to delineate the extent of the abdomen on the surface of the body. These landmarks are: the costal margin above and the pubic tubercle, anterior superior iliac spine, and iliac crest below (Fig. 4.176). The costal margin is readily palpable and separates the abdominal wall from the thoracic wall.


Anatomy_Gray

Anatomy_Gray. The costal margin is readily palpable and separates the abdominal wall from the thoracic wall. A line between the anterior superior iliac spine and the pubic tubercle marks the position of the inguinal ligament, which separates the anterior abdominal wall above from the thigh of the lower limb below. The iliac crest separates the posterolateral abdominal wall from the gluteal region of the lower limb. The upper part of the abdominal cavity projects above the costal margin to the diaphragm, and therefore abdominal viscera in this region of the abdomen are protected by the thoracic wall. The level of the diaphragm varies during the breathing cycle. The dome of the diaphragm on the right can reach as high as the fourth costal cartilage during forced expiration. How to find the superficial inguinal ring


Anatomy_Gray

Anatomy_Gray. How to find the superficial inguinal ring The superficial inguinal ring is an elongate triangular defect in the aponeurosis of the external oblique (Fig. 4.177). It lies in the lower medial aspect of the anterior abdominal wall and is the external opening of the inguinal canal. The inguinal canal and superficial ring are larger in men than in women: In men, structures that pass between the abdomen and the testis pass through the inguinal canal and superficial inguinal ring. In women, the round ligament of the uterus passes through the inguinal canal and superficial inguinal ring to merge with connective tissue of the labium majus. The superficial inguinal ring is superior to the pubic crest and tubercle and to the medial end of the inguinal ligament:


Anatomy_Gray

Anatomy_Gray. The superficial inguinal ring is superior to the pubic crest and tubercle and to the medial end of the inguinal ligament: In men, the superficial inguinal ring can be easily located by following the spermatic cord superiorly to the lower abdominal wall—the external spermatic fascia of the spermatic cord is continuous with the margins of the superficial inguinal ring. In women, the pubic tubercle can be palpated and the ring is superior and lateral to it. The deep inguinal ring, which is the internal opening to the inguinal canal, lies superior to the inguinal ligament, midway between the anterior superior iliac spine and pubic symphysis. The pulse of the femoral artery can be felt in the same position but below the inguinal ligament. Because the superficial inguinal ring is the site where inguinal hernias appear, particularly in men, the ring and related parts of the inguinal canal are often evaluated during physical examination. How to determine lumbar vertebral levels


Anatomy_Gray

Anatomy_Gray. How to determine lumbar vertebral levels Lumbar vertebral levels are useful for visualizing the positions of viscera and major blood vessels. The approximate positions of the lumbar vertebrae can be established using palpable or visible landmarks (Fig. 4.178): A horizontal plane passes through the medial ends of the ninth costal cartilages and the body of the LI vertebra—this transpyloric plane cuts through the body midway between the suprasternal (jugular) notch and the pubic symphysis. A horizontal plane passes through the lower edge of the costal margin (tenth costal cartilage) and the body of the LIII vertebra—the umbilicus is normally on a horizontal plane that passes through the disc between the LIII and LIV vertebrae. A horizontal plane (supracristal plane) through the highest point on the iliac crest passes through the spine and body of the LIV vertebra; A plane through the tubercles of the crest of the ilium passes through the body of the LV vertebra.


Anatomy_Gray

Anatomy_Gray. A plane through the tubercles of the crest of the ilium passes through the body of the LV vertebra. Visualizing structures at the LI The LI vertebral level is marked by the transpyloric plane, which cuts transversely through the body midway between the jugular notch and pubic symphysis, and through the ends of the ninth costal cartilages (Fig. 4.179). At this level are: the beginning and upper limit of the end of the duodenum, the hila of the kidneys, the neck of the pancreas, and the origin of the superior mesenteric artery from the aorta. The left and right colic flexures also are close to this level. Visualizing the position of major Each of the vertebral levels in the abdomen is related to the origin of major blood vessels (Fig. 4.180): The celiac trunk originates from the aorta at the upper border of the LI vertebra. The superior mesenteric artery originates at the lower border of the LI vertebra. The renal arteries originate at approximately the LII vertebra.


Anatomy_Gray

Anatomy_Gray. The superior mesenteric artery originates at the lower border of the LI vertebra. The renal arteries originate at approximately the LII vertebra. The inferior mesenteric artery originates at the LIII vertebra. The aorta bifurcates into the right and left common iliac arteries at the level of the LIV vertebra. The left and right common iliac veins join to form the inferior vena cava at the LV vertebral level. Using abdominal quadrants to locate The abdomen can be divided into quadrants by a vertical median plane and a horizontal transumbilical plane, which passes through the umbilicus (Fig. 4.181): The liver and gallbladder are in the right upper quadrant. The stomach and spleen are in the left upper quadrant. The cecum and appendix are in the right lower quadrant. The end of the descending colon and sigmoid colon are in the left lower quadrant.


Anatomy_Gray

Anatomy_Gray. The stomach and spleen are in the left upper quadrant. The cecum and appendix are in the right lower quadrant. The end of the descending colon and sigmoid colon are in the left lower quadrant. Most of the liver is under the right dome of the diaphragm and is deep to the lower thoracic wall. The inferior margin of the liver can be palpated descending below the right costal margin when a patient is asked to inhale deeply. On deep inspiration, the edge of the liver can be felt “slipping” under the palpating fingers placed under the costal margin. A common surface projection of the appendix is McBurney’s point, which is one-third of the way up along a line from the right anterior superior iliac spine to the umbilicus. Defining surface regions to which pain from the gut is referred


Anatomy_Gray

Anatomy_Gray. McBurney’s point, which is one-third of the way up along a line from the right anterior superior iliac spine to the umbilicus. Defining surface regions to which pain from the gut is referred The abdomen can be divided into nine regions by a midclavicular sagittal plane on each side and by the subcostal and intertubercular planes, which pass through the body transversely (Fig. 4.182). These planes separate the abdomen into: three central regions (epigastric, umbilical, pubic), and three regions on each side (hypochondrium, flank, groin). Pain from the abdominal part of the foregut is referred to the epigastric region, pain from the midgut is referred to the umbilical region, and pain from the hindgut is referred to the pubic region. Where to find the kidneys The kidneys project onto the back on either side of the midline and are related to the lower ribs (Fig. 4.183): The left kidney is a little higher than the right and reaches as high as rib XI.


Anatomy_Gray

Anatomy_Gray. The kidneys project onto the back on either side of the midline and are related to the lower ribs (Fig. 4.183): The left kidney is a little higher than the right and reaches as high as rib XI. The superior pole of the right kidney reaches only as high as rib XII. The lower poles of the kidneys occur around the level of the disc between the LIII and LIV vertebrae. The hila of the kidneys and the beginnings of the ureters are at approximately the LI vertebra. The ureters descend vertically anterior to the tips of the transverse processes of the lower lumbar vertebrae and enter the pelvis. Where to find the spleen The spleen projects onto the left side and back in the area of ribs IX to XI (Fig. 4.184). The spleen follows the contour of rib X and extends from the superior pole of the left kidney to just posterior to the midaxillary line. Fig. 4.1 Abdomen. A. Boundaries. B. Arrangement of abdominal contents. Inferior view.


Anatomy_Gray

Anatomy_Gray. Fig. 4.1 Abdomen. A. Boundaries. B. Arrangement of abdominal contents. Inferior view. Fig. 4.2 The abdomen contains and protects the abdominal viscera. Fig. 4.3 The abdomen assists in breathing. InspirationExpirationDiaphragmRelaxation of diaphragmContraction ofdiaphragmContraction of abdominal musclesRelaxation ofabdominalmuscles Fig. 4.4 Increasing intraabdominal pressure to assist in micturition, defecation, and childbirth. Laryngeal cavity closedAir retained in thoraxFixed diaphragmContraction of abdominal wallIncrease inintraabdominalpressureMicturitionChild birthDefecation Fig. 4.5 Abdominal wall. A. Skeletal elements. B. Muscles. Fig. 4.6 The gut tube is suspended by mesenteries. Branch of aortaGastrointestinal tractAortaDorsal mesenteryVentral mesenteryKidney—posterior toperitoneumVisceral peritoneumParietal peritoneum Fig. 4.7 A series showing the progression (A to C) from an intraperitoneal organ to a secondarily retroperitoneal organ.


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Anatomy_Gray. Fig. 4.7 A series showing the progression (A to C) from an intraperitoneal organ to a secondarily retroperitoneal organ. MesenteryVisceral peritoneumGastrointestinal tractGastrointestinal tractGastrointestinal tractParietal peritoneumArtery to gastrointestinal tractRetroperitoneal structuresMesentery before fusion with wallIntraperitoneal part of gastrointestinal tractSecondary retroperitoneal part of gastrointestinal tract ABC Fig. 4.8 Inferior thoracic aperture and the diaphragm. Fig. 4.9 Pelvic inlet. Ala of sacrumS IL VPelvic inletInguinal ligamentPelvic bone Fig. 4.10 Orientation of abdominal and pelvic cavities. Thoracic wallAxis of abdominal cavityAbdominal cavityPelvic cavityPelvic inletAxis of pelvic cavity Fig. 4.11 The abdominal cavity is continuous with the pelvic cavity. RectumPeritoneumPelvic inletBladderUterusShadow of ureterShadow of internal iliac vessels Fig. 4.12 Structures passing between the abdomen and thigh.


Anatomy_Gray

Anatomy_Gray. RectumPeritoneumPelvic inletBladderUterusShadow of ureterShadow of internal iliac vessels Fig. 4.12 Structures passing between the abdomen and thigh. Fig. 4.13 A series (A to H) showing the development of the gut and mesenteries. Fig. 4.14 Innervation of the anterior abdominal wall. Fig. 4.15 Inguinal region. A. Development. B. In men. C. In women. Inferior vena cavaRight testicular arteryLeft testicular arteryRight testicular veinLeft testicular veinAortaPelvic brimLeft ductus deferensDuctus deferensInguinal canalSuperficial inguinal ringDeep inguinal ringSpermatic cordRemnant ofgubernaculumEpididymisTestisTunica vaginalisTesticularartery and veinBInferior vena cavaAortaLeft renal arteryLeft ovarian arteryLeft renal veinLeft ovarian veinPelvic inletUterine tubeRound ligament of uterus (remnantsof gubernaculum)UterusSuperficialinguinal ringC Fig. 4.16 Vertebral level LI.


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Anatomy_Gray. Fig. 4.16 Vertebral level LI. Jugular notchRightkidneyLI (transpyloric)planePubic symphysisCostal marginPyloric orifice betweenstomach and duodenumPosition of umbilicus Fig. 4.17 Blood supply of the gut. A. Relationship of vessels to the gut and mesenteries. B. Anterior view. Fig. 4.18 Left-to-right venous shunts. Fig. 4.19 Hepatic portal system. Fig. 4.20 Prevertebral plexus. Sympathetic inputParasympathetic inputPrevertebral plexusLumbar splanchnicnerves (L1, L2)Pelvic splanchnic nerves (S2 to S4)Anterior and posterior vagus trunks (cranial)Greater, lesser, and least splanchnic nerves(T5 to T12) Fig. 4.21 Boundaries of the abdominal cavity. Fig. 4.22 Four-quadrant topographical pattern. Fig. 4.23 Nine-region organizational pattern. Fig. 4.24 Layers of the abdominal wall. Fig. 4.25 Superficial fascia.


Anatomy_Gray

Anatomy_Gray. Fig. 4.22 Four-quadrant topographical pattern. Fig. 4.23 Nine-region organizational pattern. Fig. 4.24 Layers of the abdominal wall. Fig. 4.25 Superficial fascia. Superficial fasciaFatty layer(Camper's fascia)Membranous layer(Scarpa's fascia)SkinPubic symphysisPenisDartos fasciaScrotumInguinal ligamentAponeurosis of external obliqueFascia lata of thigh Fig. 4.26 Continuity of membranous layer of superficial fascia into other areas. Continuity with superficialpenile fasciaContinuity withdartos fasciaExternal oblique muscleand aponeurosisMembranous layer ofsuperficial fascia (Scarpa's fascia)Attachment to fascia lataSuperficial perinealfascia (Colles' fascia)Attachment toischiopubic rami Fig. 4.27 External oblique muscle and its aponeurosis. Linea albaLatissimus dorsi muscleExternal oblique muscleAbdominal part ofpectoralis major muscleAponeurosis of external obliqueInguinal ligamentAnterior superior iliac spine Fig. 4.28 Ligaments formed from the external oblique aponeurosis.


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Anatomy_Gray. Fig. 4.28 Ligaments formed from the external oblique aponeurosis. Fig. 4.29 Ligaments of the inguinal region. Fig. 4.30 Internal oblique muscle and its aponeurosis. External oblique muscleRib XInternal oblique muscleand aponeurosisLinea albaExternal oblique muscleAponeurosis of external obliqueAnterior superior iliac spine Fig. 4.31 Transversus abdominis muscle and its aponeurosis. External oblique muscleRib XTransversus abdominismuscle and aponeurosisLinea albaExternal oblique muscleAponeurosis of internal obliqueAponeurosis of external obliqueAnterior superior iliac spine Fig. 4.32 Rectus abdominis and pyramidalis muscles. External oblique musclePosterior wall of rectus sheathRectus abdominis muscleTendinous intersectionInternal oblique muscle Arcuate lineTransversalis fasciaLinea albaPyramidalis muscle


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Anatomy_Gray. External oblique musclePosterior wall of rectus sheathRectus abdominis muscleTendinous intersectionInternal oblique muscle Arcuate lineTransversalis fasciaLinea albaPyramidalis muscle Fig. 4.33 Organization of the rectus sheath. A. Transverse section through the upper three-quarters of the rectus sheath. B. Transverse section through the lower one-quarter of the rectus sheath. Fig. 4.34 Transverse section showing the layers of the abdominal wall. Fig. 4.35 Subdivisions of the extraperitoneal fascia. Fig. 4.36 Innervation of the anterolateral abdominal wall. External oblique muscleand aponeurosisIliohypogastric nerve (L1)Xiphoid processIlio-inguinal nerve (L1)Iliac crestAnterior cutaneousbranches T7 to T12Lateral cutaneousbranches T7 to T12 Fig. 4.37 Path taken by the nerves innervating the anterolateral abdominal wall. Fig. 4.38 Dermatomes of the anterolateral abdominal wall. Fig. 4.39 Arterial supply to the anterolateral abdominal wall.


Anatomy_Gray

Anatomy_Gray. Fig. 4.38 Dermatomes of the anterolateral abdominal wall. Fig. 4.39 Arterial supply to the anterolateral abdominal wall. Fig. 4.40 Superior and inferior epigastric arteries. Fig. 4.41 Descent of the testis from week 7 (postfertilization) to birth. Fig. 4.42 Inguinal canal. Linea albaSuperficialinguinal ringDeep inguinal ringExternal oblique muscleAponeurosis of external obliqueInguinal ligamentSpermatic cordAnterior superioriliac spine Fig. 4.43 Deep inguinal ring and the transversalis fascia. Fig. 4.44 Superficial inguinal ring and the aponeurosis of the external oblique. Inguinal ligamentFemoral artery and veinExternal oblique muscleAponeurosis of external oblique Spermatic cordSuperficial inguinal ringAnterior superior iliac spine Fig. 4.45 Internal oblique muscle and the inguinal canal. Inguinal ligamentFemoral artery and veinInternal oblique muscleAponeurosis of internal oblique Spermatic cordConjoint tendonAnterior superior iliac spine


Anatomy_Gray

Anatomy_Gray. Inguinal ligamentFemoral artery and veinInternal oblique muscleAponeurosis of internal oblique Spermatic cordConjoint tendonAnterior superior iliac spine Fig. 4.46 Transversus abdominis muscle and the inguinal canal. Fig. 4.47 A. Spermatic cord (men). B. Round ligament of uterus (women). Internal spermatic fasciaParietal layer of the tunica vaginalisAVisceral layer of the tunica vaginalisCavity of the tunica vaginalisExternal spermatic fasciaCremasteric fasciaDeep inguinal ringInternaloblique muscleSuperficial inguinal ringTesticular artery andpampiniform plexus of veinsParietal peritoneumArtery to ductus deferensCremasteric vesselsGenital branch of genitofemoral nerveInferior epigastric vesselsDuctus deferensExternal obliqueaponeurosisTransversusabdominis muscleConjoint tendonExternal obliqueaponeurosisTransversalisfasciaIlioinguinalnerveIlioinguinal nerveExtraperitoneal fascia


Anatomy_Gray

Anatomy_Gray. Internaloblique muscleParietal peritoneumGenital branch ofgenitofemoral nerveGenital branch ofgenitofemoral nerveInferior epigastric vesselsRound ligament of uterusExternal obliqueaponeurosisTransversusabdominis muscleMembranous layerof superficial fasciaSuperficial fascia(fatty layers) Fine connectivetissue strandsBConjoint tendonExternal obliqueaponeurosisSkin of mons pubisIlioinguinalnerveIlioinguinal nerveExtraperitoneal fascia Fig. 4.48 Indirect inguinal hernia. Fig. 4.49 Direct inguinal hernia. Fig. 4.50 Right inguinal triangle. A. Internal view. B. Laparoscopic view showing the parietal peritoneum still covering the area. Inferior epigastricvesselsDirect herniaTesticular vesselsPosition of deepinguinal ringBLateralMedialExternal iliac vesselsDuctus deferens Fig. 4.51 Coronal CT shows a large inguinal hernia containing loops of large and small bowel (arrow) on the left side of a male patient.


Anatomy_Gray

Anatomy_Gray. Fig. 4.51 Coronal CT shows a large inguinal hernia containing loops of large and small bowel (arrow) on the left side of a male patient. Fig. 4.52 Right indirect inguinal hernia. T2, fat saturated, weighted magnetic resonance image in the coronal plane of a male groin. Fig. 4.53 A. Intraperitoneal. B. Retroperitoneal. Fig. 4.54 Greater and lesser sacs of the peritoneal cavity. Fig. 4.55 Transverse section illustrating the continuity between the greater and lesser sacs through the omental (epiploic) foramen. Fig. 4.56 Coronal CT shows ascites fluid in abdominal cavity. Fig. 4.57 Peritoneal metastasis on the surface of the liver. Computed tomogram in the axial plane of the upper abdomen. Peritoneal metastasison surface of liverAortaInferior vena cavaLiverSpleenLeft kidney Fig. 4.58 Radiograph of subdiaphragmatic gas. Fig. 4.59 Greater omentum. Fig. 4.60 Lesser omentum.


Anatomy_Gray

Anatomy_Gray. Peritoneal metastasison surface of liverAortaInferior vena cavaLiverSpleenLeft kidney Fig. 4.58 Radiograph of subdiaphragmatic gas. Fig. 4.59 Greater omentum. Fig. 4.60 Lesser omentum. Liver (retracted )GallbladderStomachLesser omentumDuodenumDescending colonAscending colonOmental foramenLesser curvature of the stomachHepatogastric ligamentHepatoduodenal ligament Fig. 4.61 Peritoneal reflections, forming mesenteries, outlined on the posterior abdominal wall. Root of the transverse mesocolonRoot of the sigmoid mesocolonRoot of the mesentery Fig. 4.62 Abdominal esophagus. RightvagusnerveTracheaArch of aortaAortaThoracicesophagusAbdominal esophagusRight crus ofdiaphragmLeft vagus nerve Fig. 4.63 Arterial supply to the abdominal esophagus and stomach. Fig. 4.64 Stomach. Fig. 4.65 Radiograph, using barium, showing the stomach and duodenum. A. Double-contrast radiograph of the stomach. B. Double-contrast radiograph showing the duodenal cap.


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Anatomy_Gray. Fig. 4.64 Stomach. Fig. 4.65 Radiograph, using barium, showing the stomach and duodenum. A. Double-contrast radiograph of the stomach. B. Double-contrast radiograph showing the duodenal cap. Fundus of stomachPyloric orificeSuperior part of duodenumABPyloric antrumEsophagusNormal duodenal capPyloric antrum of stomachInferior duodenumDuodenal jejunal flexureBody of stomachDescending part of duodenumPyloric canalPyloric sphincter Fig. 4.66 Duodenum. PancreasDuodenum—superior partDuodenum—descending partDuodenum —ascending partDuodenum—inferior partDescending colonAscending colonSpleenAbdominal aortaEsophagusL1L2L3Bile ductRight suprarenal glandRight kidneyGallbladderPosition of majorduodenal papillaPosition of minorduodenal papillaLeft kidneySuperior mesenteric vein and arteryPortal veinInferior vena cava Fig. 4.67 Arterial supply to the duodenum. Fig. 4.68 Radiograph, using barium, showing the jejunum and ileum.


Anatomy_Gray

Anatomy_Gray. Fig. 4.67 Arterial supply to the duodenum. Fig. 4.68 Radiograph, using barium, showing the jejunum and ileum. Fig. 4.69 Differences in the arterial supply to the small intestine. A. Jejunum. B. Ileum. Fig. 4.70 Ileocecal junction. A. Radiograph showing ileocecal junction. B. Illustration showing ileocecal junction and the ileocecal fold. C. Endoscopic image of the ileocecal fold. Fig. 4.71 Arterial supply to the ileum. Fig. 4.72 The endoscope is a flexible plastic tube that can be controlled from the proximal end. Through a side portal various devices can be inserted, which run through the endoscope and can be used to obtain biopsies and to perform minor endoluminal surgical procedures (e.g., excision of polyps). Fig. 4.73 Endoscopic images of the gastroesophageal junction. A. Normal. B. Esophageal cancer at esophageal junction. Fig. 4.74 Endoscopic image of the pyloric antrum of the stomach looking toward the pylorus.


Anatomy_Gray

Anatomy_Gray. Fig. 4.74 Endoscopic image of the pyloric antrum of the stomach looking toward the pylorus. Fig. 4.75 Endoscopic image showing normal appearance of the second part of the duodenum. Fig. 4.76 Small bowel visualization using MRI in coronal plane. Fig. 4.77 Axial CT shows sigmoid colon wall thickening caused by tumor. Fig. 4.78 Vasculature associated with a Meckel’s diverticulum. A. Surgical image of Meckel’s diverticulum. B. Digital subtraction angiography. Fig. 4.79 Large intestine. Transverse colonSigmoid colonAscending colonRight colic flexureAppendixCecumHaustra of colonOmental appendicesLeft colic flexureAnal canalRectumIleumTaeniae coli Fig. 4.80 Radiograph, using barium, showing the large intestine. Fig. 4.81 Position of the large intestine in the nine-region organizational pattern. Fig. 4.82 Cecum and appendix. Fig. 4.83 Mesoappendix and appendicular vessels. Fig. 4.84 Positions of the appendix. Fig. 4.85 Arterial supply to the cecum and appendix.


Anatomy_Gray

Anatomy_Gray. Fig. 4.82 Cecum and appendix. Fig. 4.83 Mesoappendix and appendicular vessels. Fig. 4.84 Positions of the appendix. Fig. 4.85 Arterial supply to the cecum and appendix. Fig. 4.86 Inflamed appendix. Ultrasound scan. Fig. 4.87 Axial CT shows inflamed appendix. Fig. 4.88 Colon. Fig. 4.89 Right and left colic flexures. Fig. 4.90 Arterial supply to the colon. Fig. 4.91 Rectum and anal canal. Fig. 4.92 Arterial supply to the rectum and anal canal. Posterior view. Fig. 4.93 Small bowel malrotation and volvulus. Radiograph of stomach, duodenum, and upper jejunum using barium. Fig. 4.94 Small bowel malrotation. Radiograph of stomach, duodenum, and jejunum using barium.


Anatomy_Gray

Anatomy_Gray. Fig. 4.94 Small bowel malrotation. Radiograph of stomach, duodenum, and jejunum using barium. Fig. 4.95 This radiograph of the abdomen, anteroposterior view, demonstrates a number of dilated loops of small bowel. Small bowel can be identified by the plicae circulares that pass from wall to wall as indicated. The large bowel is not dilated. The cause of the small bowel dilatation is an adhesion after pelvic surgery. Dilation of small bowelPlicae circulares Fig. 4.96 Coronal CT demonstrates dilated and fluid-filled loops of small bowel in patient with small bowel obstruction. Dilated and fluid-filledloops of small bowel Fig. 4.97 Coronal CT of abdomen shows fluid-filled and dilated ascending and transverse colon in patient with large bowel obstruction. Fig. 4.98 This oblique radiograph demonstrates contrast passing through a colonic stent that has been placed to relieve bowel obstruction prior to surgery.