DMH Part 1 > Structures of the Abdomen > Flashcards
Structures of the Abdomen Flashcards
Innervation of the Liver
Nerves that supply the liver arise from the hepatic nerve plexus and contain parasympathetic fibers from the vagus nerve and sympathetic fibers from T7-T10. However, other than vasoconstriction, their function remains unclear. There is apparently no effect on bile production Stimulation of afferents from swelling of the liver is due to both sympathetic afferents and innervation of the visceral and diaphragmatic peritoneum by the right phrenic nerve. The pain is felt in the epigastrum and is often referred to the shoulder.
Innervation of the Gall Bladder
- Sympathetic The afferent fibers from T6-T9 travel via the splanchnic nerves to the celiac plexus.
- Gallstones Gall bladder pain is often due to the passage and/or lodging of calculi (gallstones) in the cystic duct and bile duct. It can be very severe and have a sudden onset. Pain from the gall bladder tends to be referred to the right side of the thoracic wall in the region of the 6-9th rib and radiates back to the inferior angle of the scapula
- Parasympathetic innervation is via the vagus nerve
Characteristics of Lymph
- Lymph is extracellular fluid
- Lymph flow is generally unidirectional due to the presence of valves in lymph vessels
- Lymph flows along the arterial supply route to an organ, but in the opposite direction
- Lymph flows by
Filtration pressure
Contractions of muscles
Pulsations of vessels
Contraction of smooth muscle
Negative pressure in thorax
-Common route of cancer metastasis
Esophagus
•The esophagus is a muscular tube, approximately 25cm in length and 2 cm in diameter that extends from the pharynx to the stomach. Only the last 1-2 cm is in the abdomen. Its primary function is to convey food from the mouth to the stomach. It is composed of two muscle layers - an external longitudinal layer and inner circular layer. The external layer is composed of either skeletal muscle (upper third), both skeletal and smooth muscle (middle third) or entirely smooth muscle (lower third).
Stricture Points for the Esophagus
•The thoracic esophagus descends through the thoracic cavity posterior to the trachea, posterior and to the right of the arch of the aorta, and posterior to the left atrium. The esophagus has three areas of constriction where swallowed items may lodge. These include:
1) the arch of the aorta
2) the left main bronchus
3) as it passes through the diaphragm.
Esophageal Hiatus
- The esophagus enters abdomen through the esophageal hiatus of diaphragm at the level of T10.
- Other structures that pass through the esophageal hiatus are branches of the vagus nerve, the esophageal nerve plexus and esophageal branches of the gastric vessels.
Esophageal or Cardial Sphincter
- The esophageal or cardial sphincter is a physiologic sphincter (as opposed to a structure) that helps prevent reflux of stomach contents into the esophagus.
- The esophagus enters the stomach at the esophagogastric junction creating the cardial orifice.
Barrett’s Esophagus
- Barrett’s esophagus results from the reflux of gastric contents into the lower esophagus.
- The continuous irritation of the esophageal epithelium results in conversion of the epithelium from stratified squamous to columnar epithelium. Barrett’s esophagus is associated with the development of esophageal cancer.
Blood Supply of the Thoracic Esophagus
•Arteries
-The arterial supply of the thoracic esophagus is from multiple branches of the thoracic aorta.
•Veins
-The venous drainage of the thoracic esophagus is through the azygos system of veins, including the hemiazygos, the accessory hemiazygos, and the azygos vein, as well as through the intercostal veins.
Blood Supply of the Abdominal Esophagus
•Arteries
-The arterial supply of the abdominal esophagus is from the left gastric artery that is a branch of the celiac trunk off the abdominal aorta. In addition, the left inferior phrenic a. arises from the abdominal aorta to the esophagus.
•Veins
-The venous drainage of the abdominal esophagus is from the left gastric vein into the portal vein that traverses the hepatic portal system. In addition, some blood enters systemic veins and drains via the azygous system with blood from the thoracic esophagus.
Esophageal Varices
•In the esophagus, the azygos system, together with the hepatic portal system, forms the basis for the portal-systemic anastomoses that can result in esophageal varices (engorgement of veins in the submucosa of the esophagus). This can occur in cases of portal hypertension (e.g. cirrhosis of the liver); the esophageal veins can become greatly enlarged and engorged and may bleed copiously.
Innervation of the Esophagus
- Parasympathetic innervation of the esophagus is via the anterior and posterior vagal trunks.
- Sympathetic innervation is from the thoracic sympathetic trunks that form the greater splanchnic nerve. The parasympathetic and sympathetic nerves form the esophageal nerve plexus on the distal part of the esophagus.
Stomach Divisions
•The stomach is a dilation of the digestive tract that serves as a reservoir for food and a site for secretion of hydrochloric acid, enzymes and hormones which stimulate other parts of the digestive tract. It is divided into several parts:
a. Cardial portion- surrounds the cardial orifice
b. Fundus- superior portion of the stomach which is related to the left dome of the diaphragm
c. Body - is the bulk of the stomach that lies between the fundus and the pyloric antrum
d. Pyloric portion - is composed of the wider pyloric antrum that leads to the pyloric canal. The opening of the stomach into the duodenum is called the pyloric orifice. The pyloric sphincter that creates the orifice is a true sphincter composed of circular muscle fibers and controls gastric emptying into the duodenum.
External Surface of Stomach
a. Lesser curvature which forms the short border of the upper part of the stomach,
b. Angular incisure is an indentation at the junction of the body and pyloric portion of the stomach.
c. Greater curvature is the long border on inferior portion of the stomach
d. Cardial incisure is an indentation between the esophagus and the fundus.
Rugae
The internal surface of the stomach is highly folded into rugae or gastric folds that increase the surface area of the stomach and direct the flow of stomach contents.
Muscle Layers of the Stomach
The stomach contains three muscle layers :
- outer longitudinal layer
- middle circular layer
- innermost oblique layer The oblique muscle fibers of the stomach create the gastric canal on the lesser curvature.
Anterior and Posterior Relations of the Stomach
- Anteriorly, the stomach is related to the left lobe of the liver, the diaphragm, and the anterior abdominal wall.
- Posteriorly, the stomach is related to the lesser sac (omental bursa) and the pancreas. A gastric ulcer that perforates on the posterior surface of the stomach would empty stomach contents into the lesser sac.
Blood Supply of the Stomach - Arteries
•Arteries.
- The arterial supply of the stomach is extremely rich and is derived from the first abdominal branch of the aorta, the celiac trunk.
- The left gastric artery arises from the celiac trunk and ascends to the cardia. It then courses along the lesser curvature of the stomach.
- The splenic artery branches off the celiac trunk and courses behind the stomach. The left gastro-omental branches off the splenic and then courses along the greater curvature of the stomach. The short gastric arteries branch from the distal end of the splenic and supply the fundus of the stomach.
- The common hepatic artery branches off the celiac trunk that branches to form the proper hepatic artery and the gastroduodenal artery. The right gastric artery branches off the proper hepatic and ascends up the lesser curvature of the stomach. The right gastro-omental artery branches off the gastroduodenal artery and ascends up the greater curvature of the stomach.
- The arteries of the stomach form arterial arcades that form extensive anastomoses. The right and left gastric a. anastomose along the lesser curvature and the right and left gastroomental a. anastomose on the greater curvature. These arcades also give off gastric branches to both surfaces of the stomach, and these branches anastomose to link the two arcades.
Blood Supply of the Stomach - Veins
•Veins
-Venous drainage of the stomach largely parallels the arteries. The right and left gastric veins drain into the portal vein. The short gastric and left gastroomental veins empty into the splenic vein. The right gastroomental vein drains into the superior mesenteric vein. The splenic vein and the superior mesenteric vein join to form the hepatic portal vein.
Innervation of the Stomach
•Parasympathetic: anterior (from left vagus n.) and posterior (from right vagus n.) vagal trunks. Parasympathetic stimulation causes:
- stimulation of gastric acid secretion
- stimulation of peristalsis
- increased glandular secretion
- relaxation of pyloric sphincter
- vasodilation
- sensory from abdominal viscera (stretch)
•Sympathetic: Sympathetic fibers, T6-T9, reach the stomach from the greater splanchnic nerve through the celiac plexus. The celiac plexus is comprised of postganglionic sympathetic fibers and the two celiac ganglia. The actions of sympathetic stimulation are:
- vasoconstriction
- contraction of pyloric sphincter
- inhibition of peristalsis and secretion
•Pain from stomach lesions (i.e. gastric peptic ulcer) will be referred (via sympathetic afferents) to the epigastric and left hypochondriac regions of the body.
Small Intestine - Duodenum
•The widest, shortest and most fixed part of the small intestine, the duodenum forms a C around the head of the pancreas. Most of the digestion of food occurs in the duodenum. It is divided into:
- Superior part is just distal to the pylorus of the stomach. This part of the duodenum is also called the duodenal cap or ampulla by radiologists due to its prominence in x-rays.
- Descending part. Receives the bile duct and the main pancreatic duct. The ducts unite to form the hepatopancreatic ampulla that opens into the duodenum on the major duodenal papilla. Surrounding the hepatopancreatic ampulla and the terminal portions of the bile duct and main pancreatic duct is a smooth muscle layer called the sphincter of the hepatopancreatic ampulla. Superior to the major duodenal papilla is the minor duodenal papilla, the opening of the accessory pancreatic duct.
- The horizontal part extends across the posterior abdominal wall at approximately L3.
- Ascending part emerges from the retroperitoneal space and is continuous with the jejunum.
Duodenum Blood Supply - Arteries
•Arteries
- The blood supply of the duodenum is derived from two major branches of the abdominal aorta. The portion proximal to the entry of the bile duct is supplied from the celiac trunk. The celiac trunk gives off the common hepatic artery that forms the gastroduodenal artery that branches to form the superior pancreaticoduodenal a. (arterial arcades)
- In addition, the superior mesenteric a. arises from the abdominal aorta and branches to form the inferior pancreaticoduodenal arteries (arterial arcades) that supply the portion of the duodenum distal to the entry of the bile duct.
Duodenum Blood Supply - Veins
•Veins
-The venous drainage of the duodenum parallels the arteries, and empties into the hepatic portal vein.
Innervation of the Duodenum
•Parasympathetic innervation of the duodenum is derived from the vagus nerve. Sympathetic innervation (T5-T9) of the duodenum is via the celiac and superior mesenteric plexuses. Pain from a duodenal ulcer will be referred to the epigastric region.
Jejunum and Ileum
- With the duodenum, the jejunum and ileum make up the small intestine. The jejunum and ileum are peritoneal structures and extremely long (in an adult, approximately 22 feet). Most of the absorption of digested nutrients and water occurs in the jejunum and ileum. An average sized individual takes in 1-2 liters of dietary fluid each day; another 6-7 liters is received by the small intestine as secretions from salivary glands, stomach, pancreas and the small intestine itself. However, by the time the intestinal contents reach the large intestine, about 80% of this fluid has been reabsorbed. Consequently, diarrhea is most often caused by a failure to reabsorb water in the small intestine.
- The jejunum is the first part of the post-duodenal small intestine. There is no clear demarcation of the ileojejunal junction, and the jejunum is defined as the proximal 2/5 of the combined length. It occupies the upper left quadrant of the abdomen. The interior of the jejunum is thrown into folds called the plicae circularis. (Netter 272) The ileum is the distal 3/5 of the post-duodenal small intestine. For the most part, the ileum resides in the right lower quadrant. It is distinguished from the jejunum by its smaller diameter and fewer plicae circularis.
- The ileum joins the large intestine at the ileocolic junction. The ileum enters the cecum at an oblique angle and the ileocecal valve surrounds the orifice.
Blood supply of the jejunum and ileum
•Arteries
-The arterial supply to the jejunum and ileum is derived exclusively from the superior mesenteric artery that gives off jejunal and ileal arcades. In addition, the terminal portion of the ileum receives blood from the ileocolic branch of the superior mesenteric artery.
•Veins
-The venous drainage of the jejunum and ileum parallels the arteries, with unnamed intestinal veins draining into the superior mesenteric vein. In addition, the ileal branch of the ileocolic vein drains into the superior mesenteric vein.
Innervation of the Jejunum and Ileum
•Sympathetic efferents from (T8)T9-T10(11)
- Vasoconstriction
- Contraction of sphincters
- Inhibition of secretion
- Inhibition of peristalsis
- Sympathetic afferents (T8)T9-T10(11)
- Pain from the jejunum and ileum is referred to the periumbilical region of the anterior body wall.
- Parasympathetic innervation is derived from the posterior vagal trunks. Parasympathetic stimulation has the opposite effect of sympathetic stimulation, causing increased mobility and secretion.
Large Intestine
- The large intestine makes an inverted “C” in the abdominal cavity. Because much of the large intestine is peritoneal (suspended by a mesentery), the position of the different parts of the large intestine may vary greatly.
- The large intestine (Netter 263, 276) begins at the ileocecal junction and ends at the rectum and the anal canal. It is distinguished from the small intestine by:
- its larger diameter,
- the presence of teniae coli, which are three thickened bands of longitudinal smooth muscle, as well as
- the presence of omental appendices, which are fatty projections attached to the exterior surface and
- the large intestine is thrown into sacculations called haustra between the teniae coli.
Cecum
•The cecum is the blind sac-like end of the proximal large intestine. It lies in the right lower quadrant in the iliac fossa. The cecum is covered in peritoneum and is mobile, but it does not contain a mesentery. The terminal ileum enters the cecum at the ileocecal junction and forms the ileocecal valve. This valve is thought to prevent reflux of materials from the colon to the ileum. The vermiform appendix is a blind worm-like diverticulum (5-10 cm) that is attached to the cecum inferior to the ileocecal orifice. The appendix has a short mesentery called the mesoappendix. The appendix can project in many directions from the cecum, but most often projects downward over the pelvic brim.
Ascending Colon
- The ascending colon lies on the right side of the abdominal cavity and extends from the cecum to the right lobe of the liver. It ends at right colic flexure.
- Although the ascending colon is generally retroperitoneal, in approximately 25% of cases it is suspended by a mesentery.
Transverse Colon
- The transverse colon is the largest and most mobile part of the large intestine. It is suspended by the transverse mesocolon. It extends across the abdomen from the right colic flexure to the left colic flexure.
- Because of its mobility, the position of the transverse colon is variable.
Descending Colon
•The descending colon extends down the left side of the abdominal cavity from the left colic flexure to the left iliac fossa. The descending colon is retroperitoneal, but there may be a short mesentery in its most terminal portion.
Sigmoid Colon
•The sigmoid colon is continuous with the descending colon and ends at the rectum. It is a S-shaped loop that is suspended by the sigmoid mesocolon.
Blood Supply of the Large Intestine - Arteries
•The arterial supply of the large intestine is derived from the superior mesenteric and inferior mesenteric arteries.
The cecum is supplied by the ileocolic artery, which is the terminal branch of the superior mesenteric artery. The appendix is supplied by the appendicular artery, a branch of the ileocolic artery.
- The ascending colon and right colic flexure are supplied by the right colic artery, a branch of the superior mesenteric artery.
- The transverse colon is primarily supplied by the middle colic artery from the superior mesenteric artery. However, it also receives blood from the left and right colic arteries.
- The descending colon is supplied by the left colic artery, a branch of the inferior mesenteric artery.
- The sigmoid colon is supplied by the sigmoid arteries, branches of the inferior mesenteric artery.
- There is a high degree of anastomoses within the arteries of the intestine, resulting in the formation of the marginal artery along the wall of the large intestine.
Blood Supply of the Large Intestine - Veins
- The venous drainage of the both the small and large intestine is almost exclusively via the hepatic portal system.
- The venous drainage parallels the arterial supply, with the ileocolic, right colic and middle colic veins draining into the superior mesenteric vein. The left colic and sigmoid veins drain into the inferior mesenteric vein that empties into the splenic vein. The superior mesenteric vein joins the splenic vein to form the hepatic portal vein.
Innervation of the Large Intestine
- Parasympathetic fibers to approximately the left colic flexure are derived from the vagus nerve. The rest of the intestine is supplied by sacral parasympathetic fibers (S2-S4).
- Sympathetic innervation is derived from T10 to L1 to the left colic flexure. L1, 2 from left colic flexure to rectum. Despite its localization throughout the abdominal cavity, pain from the colon is mostly felt in the hypogastric region.
Rectum
- The rectum is the fixed (primarily retroperitoneal) terminal part of the large intestine that lies in the pelvic cavity. It is continuous with the sigmoid colon just anterior to the S3 vertebra and ends at the anal canal.
- The rectum has several flexures. The portion of the rectum that follows the curve of the sacrum and the coccyx is called the sacral flexure. The rectum ends at a sharp angle as the gut perforates the pelvic diaphragm (levator ani muscle) at the anorectal flexure. This flexure is an important component of fecal continence.
- There are three lateral flexures of the rectum (the superior, intermediate, and inferior) that result from infoldings on the internal surface of the rectum.
- Distal to the inferior rectal fold, the rectum expands to form the ampulla. The ampulla receives and holds fecal materials until defecation. The ability of the ampulla to relax to accommodate fecal matter is another important component of fecal continence.
Vasculature of the Rectum
- The rectum receives arterial supply from several sources. The superior rectal artery is the continuation of the inferior mesenteric artery. The right and left middle rectal arteries arise from the internal iliac arteries. Finally, the inferior rectal arteries arise from the internal pudendal arteries in the pelvis.
- Venous drainage of the rectum enters into both the portal and systemic systems, so the rectum is an important site of portal-systemic anastomoses. The superior rectal vein drains into the inferior mesenteric vein and subsequently into the portal vein, whereas the middle and inferior rectal veins drain into the systemic veins. Furthermore, all of these veins form the internal and external rectal venous plexuses.
Innervation of the Rectum
- The sympathetic nervous supply is from the lumbar spinal cord (l1, L2) via the lumbar splanchnic nerves, the hypogastric plexus, and the periarterial plexus of the inferior mesenteric artery.
- Parasympathetic innervation is via S2-S4 via the pelvic splanchnic nerves and the inferior hypogastric plexuses. Visceral afferents follow the parasympathetic fibers to the S2-S4 spinal sensory ganglia.
Anal Canal
- The anal canal is the terminal part of the large intestine. The canal (2.5-3.5 cm in length) begins where the intestinal tract perforates the levator ani muscle. Muscles of the anal canal are central to the control of fecal continence.
- There are two sphincters that control the anal canal. The internal anal sphincter is an involuntary sphincter. This sphincter remains contracted by sympathetic stimulation and is inhibited by parasympathetic stimulation. The external anal sphincter is a voluntary sphincter that is separated into 3 zones, the subcutaneous, superficial, and deep parts. The external anal sphincter blends with the portion of the levator ani muscle called the puborectalis.
Defecation
- When fecal material enters the ampulla of the rectum, distension causes relaxation of the internal anal sphincter.
- Voluntary contraction of the external anal sphincter and the puborectalis muscle maintain continence.
- Defecation results from parasympathetic inhibition of the internal anal sphincter and voluntary relaxation of the external anal sphincter and the puborectalis muscle
Pectinate Line
- The anal canal is also characterized by the presence of longitudinal ridges called anal columns, which contain the terminal branches of the superior rectal artery and vein.
- Where the anal columns terminate is the pectinate line. The pectinate line is a critical anatomical landmark, as the vascular, lymphatic and nerve supplies differ above and below the line.
Above the Pectinate Line
- Superior rectal artery and vein (inferior mesenteric artery and vein; portal system)
- Visceral motor and sensory innervation
- Lymphatics drain to internal iliac lymph nodes
Below the Pectinate Line
- Inferior rectal artery and vein (caval venous system)
- Somatic motor and sensory innervation
- Lymphatics drain to superficial inguinal lymph nodes
Blood Supply of the Anal Canal
•Arteries
-The arterial supply of the anal canal is provided by superior, middle and inferior rectal arteries.
•Veins
-Like the rectum, the venous drainage of the anal canal is via the internal and external venous plexuses. Internal hemorrhoids result from prolapse of the rectal mucosa around the internal venous plexus, whereas external hemorrhoids form in the external venous plexus.
Innervation of the Rectal Canal
•Superior to the pectinate line: visceral innervation via the inferior hypogastric plexus Inferior to the pectinate line: inferior rectal nerve
Inflammatory Bowel Disease
- Approximately 1.5 million people in the US have been diagnosed with some form of inflammatory bowel disease (IBD).
- Inflammatory bowel disease is an uncontrolled inflammation of the intestine.
- Ulcerative colitis is restricted to the colon and rectum, whereas Crohn’s disease can affect anywhere along the length of the GI tract, although the small intestine and colon are most common.
Pancreas
•The pancreas is an elongated organ that is retroperitoneal and extends from the C-curve of the duodenum (head) to the tail, which may extend into the lienorenal ligament.
The uncinate process extends from the inferior part of the head behind the superior mesenteric artery.
- The neck of the pancreas is constricted by the superior mesenteric artery and vein.
- The body of the pancreas forms part of the stomach bed and is in contact with the aorta, superior mesenteric artery, the left suprarenal gland, and the left kidney
Pancreas - Function
- The pancreas is a gland that has both endocrine (insulin, glucagon, somatostatin) and exocrine (digestive enzymes, bicarbonate) components.
- The exocrine products reach the duodenum via the main pancreatic duct that begins in the tail of the pancreas and joins with the bile duct to form the hepatopancreatic ampulla.
- The accessory pancreatic duct drains the uncinate process and the inferior portion of the head and opens into the duodenum at the minor duodenal papilla. The accessory pancreatic duct usually communicates with the main pancreatic duct in the head of the pancreas.
Blood Supply of the Pancreas
•Arteries
-The arterial supply of the pancreas is mostly derived from the splenic artery, which forms arcades with pancreatic branches of the gastroduodenal a. and superior mesenteric artery. The body and tail of the pancreas are supplied by many branches of the splenic artery. The superior pancreaticoduodenal a. and inferior pancreaticoduodenal a. supply the head of pancreas.
•Veins
The venous drainage of the pancreas parallels the arterial supply (see also venous drainage of duodenum). The body and tail are drained by small veins that empty into the splenic v.
Innervation of the Pancreas
- Sympathetic innervation of the pancreas is via the thoracic splanchnic nerves and is derived from T5-T9. They provide innervation to blood vessels and also to the acinar cells and islets.
- Parasympathetic innervation is derived from the vagus nerve and supplies the acinar cells. They may stimulate secretion of pancreatic enzymes.
- Pain from the pancreas is often felt in the epigastric region and middle back.
Liver
- The liver is the largest gland in the body and has a vast number of functions that include detoxification of ingested materials, absorption of digested food, storage of glycogen, synthesis of blood proteins, and mucosal immunity.
- The liver lies in the right upper quadrant directly under the thoracic cage and diaphragm.
- Normally, the liver is deep to ribs 7-11 and extends across the midline toward the left nipple. Thus, the liver fills the right hypochondrium and upper epigastrium and extends into the left hypochondrium.
- The liver is divided up into the visceral and diaphragmatic surfaces.
-The visceral surface is in contact with the abdominal organs whereas the diaphragmatic surface is in contact with the diaphragm.
Lobes of the Liver
- Right lobe
- Left lobe
- Quadrate lobe
- Caudate lobe
Porta Hepatis
•The portal vein, hepatic artery, and hepatic ducts enter and exit the liver on the visceral surface at the porta hepatis.
Blood Supply of the Liver
•Arteries
-The common hepatic artery from the celiac trunk gives off the proper hepatic artery. The proper hepatic artery divides to form the right and left hepatic arteries. The blood flowing into the liver is derived from both the portal vein (70%) and the hepatic artery (30%). The contribution from the hepatic artery is essential, as it supplies oxygenated blood.
•Veins
-Blood in the liver sinusoids (from the hepatic a. and portal v) empties into the hepatic veins (rt., middle, and lt.) which drain almost immediately after exiting the liver into the inferior vena cava.
Innervation of the Liver
- Nerves that supply the liver arise from the hepatic nerve plexus and contain parasympathetic fibers from the vagus nerve and sympathetic fibers from T7-T10. However, other than vasoconstriction, their function remains unclear. There is apparently no effect on bile production
- Stimulation of afferents from swelling of the liver is due to both sympathetic afferents and innervation of the visceral and diaphragmatic peritoneum by the right phrenic nerve.
- The pain is felt in the epigastrum and is often referred to the shoulder.
Hepatic Duct System
•Bile is excreted by individual liver cells into bile canaliculi that progressively unite to form larger and larger bile ducts within the substance of the liver. These ducts unite to form the left and right hepatic ducts that exit the liver at the porta hepatis. These ducts unite to form the common hepatic duct. The common hepatic duct joins the cystic duct from the gall bladder to form the bile duct (a.k.a. common bile duct, biliary duct).
Gall Bladder
•The gall bladder (Netter 280) is a small sac that lies on the visceral surface of the liver and is in contact with the first part of the duodenum and the transverse colon. It functions to store and concentrate bile.
It is composed of several parts:
- Fundus
- Body
- Neck
- Cystic duct
- Spiral valve
- The most distal part of the bile duct has a thickened muscle sphincter. When this sphincter contracts, bile cannot enter the duodenum and backs up into the gall bladder for storage.
- Contraction of the gall bladder to expel bile into the duodenum is controlled by the hormone cholecystokinin secreted by the intestinal mucosa.
Blood Supply of the Gall Bladder
•Arteries
-The cystic artery is the main arterial supply to the gall bladder. It is a branch of the right hepatic artery.
•Veins
-Venous drainage of the gall bladder is into substance of liver, joining with branches of the portal vein.
Innervation of the Gall Bladder
•Sympathetic
-The afferent fibers from T6-T9 travel via the splanchnic nerves to the celiac plexus.
•Parasympathetic innervation is via the vagus nerve.
Gallstones
- Gall bladder pain is often due to the passage and/or lodging of calculi (gallstones) in the cystic duct and bile duct. It can be very severe and have a sudden onset.
- Pain from the gall bladder tends to be referred to the right side of the thoracic wall in the region of the 6-9th rib and radiates back to the inferior angle of the scapula
Spleen
- The spleen lies to the left of the stomach, situated in the greater omentum and dividing that structure into the gastrolienal and lienorenal ligaments.
- These two ligaments attach to the hilum (the longitudinal fissure on the visceral surface of the spleen) to form the splenic pedicle.
- The vessels and nerves of the spleen also enter at the hilum. The spleen is described by its diaphragmatic, gastric, renal, and colic surfaces.
- The spleen is a lymphoid organ that functions in the removal of senescent blood cells, filters antigens from the blood, and aids in mounting an immune response.
Blood Supply of the Spleen
•Arteries
-The splenic artery is the largest branch of the celiac trunk. It is quite tortuous and passes posterior to the stomach. It is often embedded in the superior part of the pancreas.
•Veins
-The splenic vein drains the spleen. The splenic vein unites with the superior mesenteric vein to form the hepatic portal vein.
Innervation of the Spleen
- Sympathetic innervation reaches the spleen via the celiac ganglia. Stimulation produces contraction of the spleen, forcing red cells into the circulation.
- There appears to be no parasympathetic innervation of the spleen.
Lymphatic Drainage
a. Stomach, Small Intestine, Duodenum and Pancreas
- Lymphatic drainage of these structures is to the celiac and superior mesenteric nodes and then into the cisterna chili.
b. Large Intestine
- Lymphatic drainage of the Large Intestine is via the superior and inferior mesenteric nodes.
c. Rectum
- The rectum is drained by the inferior mesenteric, pararectal, and sacral nodes.
d. Anal canal
- Above the pectinate line, drainage is the to internal iliac lymph nodes. Below the pectinate line, drainage is to the superficial inguinal lymph nodes.
Portal-Systemic Anastomoses
The hepatic portal system does have connection with the systemic circulation at sites other than the liver. These anastomoses become clinically important in cases of portal hypertension or blockage of the inferior vena cava. They are:
a. gastroesophageal region
b. anorectal region
c. paraumbilical region
d. retroperitoneal region
Referred Pain from Stomach Lesions
•Pain from stomach lesions (i.e. gastric peptic ulcer) will be referred (via sympathetic afferents) to the epigastric and left hypochondriac regions of the body.
Referred Pain from the Duodenum
•Pain from a duodenal ulcer will be referred to the epigastric region.
Referred Pain from the Jejunum and Ileum
•Pain from the jejunum and ileum is referred to the periumbilical region of the anterior body wall.
Referred Pain from the Colon
•Despite its localization throughout the abdominal cavity, pain from the colon is mostly felt in the hypogastric region.
Referred Pain from the Pancreas
•Pain from the pancreas is often felt in the epigastric region and middle back.
Referred Pain from the Liver
•The pain is felt in the epigastrum and is often referred to the shoulder.
Referred Pain from the Gall Bladder
•Pain from the gall bladder tends to be referred to the right side of the thoracic wall in the region of the 6-9th rib and radiates back to the inferior angle of the scapula.
