TBL16 - Esophagus, Stomach and Duodenum Flashcards
Where does the esophagus course? Define the function of the inferior esophageal sphincter.
1) The esophagus courses within the posterior mediastinum to enter the abdominal cavity via the esophageal hiatus of the diaphragm
2) Radiologic studies show that food stops at the inferior esophageal sphincter momentarily and that the sphincter mechanism is normally efficient in preventing reflux of gastric contents into the esophagus
3) When one is not eating, the lumen of the esophagus is normally collapsed superior to this level to prevent food or stomach juices from regurgitating into the esophagus
How does the inferior esophageal sphincter contribute to hiatal hernia formation?
1) A hiatal (hiatus) hernia is a protrusion of part of the stomach into the mediastinum through the esophageal hiatus of the diaphragm
2) The hernias occur most often in people after middle age, possibly because of weakening of the muscular part of the diaphragm and widening of the esophageal hiatus
How is pyrosis related to GERD?
1) Pyrosis (G., burning), or “heartburn,” is the most common type of esophageal discomfort or substernal pain
2) This burning sensation in the abdominal part of the esophagus is usually the result of regurgitation of small amounts of food or gastric fluid into the lower esophagus (gastroesophageal reflux disorder; GERD)
What typically causes a congenital hiatal hernia?
Occasionally, the esophagus fails to lengthen sufficiently, and the stomach is pulled up into the esophageal hiatus through the diaphragm. The result is a congenital hiatal hernia
What does the left gastric artery supply? What does the left gastric vein drain blood from and to?
1) The left gastric artery from the celiac trunk (artery) supplies the abdominal part of the esophagus
2) The left gastric vein drains blood from the abdominal part of the esophagus into the hepatic portal vein
What do some tributaries of the left gastric vein anastomose with? What does the azygos vein empty into? What creates a portal-systemic anastomosis?
1) Some tributaries of the left gastric vein anastomose with esophageal tributaries of the azygos vein
2) The azygos vein empties into the SVC
3) Thus, anastomoses between tributaries of the left gastric vein and the azygos vein create a portal-systemic anastomosis
How do esophageal varices form and why are they life-threatening?
1) In portal hypertension (an abnormally increased blood pressure in the portal venous system), blood is unable to pass through the liver via the hepatic portal vein, causing a reversal of flow in the esophageal tributary
2) The large volume of blood causes the submucosal veins to enlarge markedly, forming esophageal varices
3) These distended collateral channels may rupture and cause severe hemorrhage that is life-threatening and difficult to control surgically
Define the cardiac orifice, fundus, body, pylorus, and lesser and greater curvatures of the stomach. Interpret how the pylorus controls discharge of stomach contents into the duodenum.
1) Look at picture
2) Pylorus contracts to prevent stomach contents from entering the duodenum prematurely
Where does the common hepatic artery arise from? Where does the right gastric artery branch from and anastomose with?
1) The common hepatic artery arises from the celiac trunk and bifurcates into the proper hepatic and gastroduodenal arteries
2) The right gastric artery branches from the proper hepatic artery and anastomoses with the left gastric artery on the lesser curvature of the stomach
What is the right gastroepiploic artery a branch of? Where does it reside and what does it anastomose with?
1) The right gastroepiploic artery is a branch of the gastroduodenal artery
2) It resides on the greater curvature of the stomach where it anastomoses with the left gastroepiploic artery, a branch of the splenic artery
What do the right gastric vein and the right and left gastroepiploic veins do?
The right gastric vein and the right and left gastroepiploic veins deliver venous blood from the stomach and spleen to the hepatic portal vein
How do paraesophageal and sliding hiatal hernias differ?
1) In the less common para-esophageal hiatal hernia, the cardia remains in its normal position. However, a pouch of peritoneum, often containing part of the fundus of the stomach, extends through the esophageal hiatus anterior to the esophagus. In these cases, usually no regurgitation of gastric contents occurs because the cardial orifice is in its normal position
2) In the common sliding hiatal hernia, the abdominal part of the esophagus, the cardia, and parts of the fundus of the stomach slide superiorly through the esophageal hiatus into the thorax, especially when the person lies down or bends over. Some regurgitation of stomach contents into the esophagus is possible because the clamping action of the right crus of the diaphragm on the inferior end of the esophagus is weak
How is Helicobacter pylori infection related to gastric ulcers and why are ulcers that perforate through the posterior wall of the stomach life-threatening?
1) Gastric ulcers are open lesions of the mucosa of the
stomach
2) People experiencing severe chronic anxiety are most prone to the development of peptic ulcers. They often have gastric acid secretion rates that are markedly higher than normal between meals
3) It is thought that the high acid in the stomach overwhelms the bicarbonate normally produced by the duodenum and reduces the effectiveness of the mucous lining, leaving it vulnerable to H. pylori
4) A posterior gastric ulcer may erode through the stomach wall into the pancreas, resulting in referred pain to the back. In such cases, erosion of the splenic artery results in severe hemorrhage into the peritoneal cavity
What constitutes the small intestine? What shape does the duodenum take?
1) The duodenum, jejunum, and ileum constitute the small intestine
2) The duodenum takes a C-shaped course around the head of the pancreas
Where are the superior (1st) and proximal portion of the descending (2nd) part of the duodenum derived from? Where are the distal portion of the 2nd part and the horizontal (3rd) and ascending (4th) parts derived from?
1) The superior (1st) part and proximal portion of the descending (2nd) part of the duodenum are intraperitoneal foregut derivatives
2) The distal portion of the 2nd part and the horizontal (3rd) and ascending (4th) parts are retroperitoneal midgut derivatives
What structures are found on the anterior surface of the 1st, 2nd, and 3rd parts of the duodenum? What structures are found on the posterior surface of the 1st, 2nd, and 3rd parts of the duodenum?
1) Anterior surface:
a) 1st part: Liver and gallbladder
b) 2nd part: Transverse colon
c) 3rd part: SMA
2) Posterior surface
a) 1st part: Gastroduodenal artery
b) 2nd part: Right kidney
c) 3rd part: Aorta
What is the superior pancreaticoduodenal artery a branch of? What does it supply? What else supplies this structure and what is this artery a branch of? Where does venous blood that comes from the duodenum drain into?
1) The superior pancreaticoduodenal artery, a branch of the gastroduodenal artery, supplies the duodenum, which is also supplied by the inferior pancreaticoduodenal artery, a branch of the SMA
2) Venous blood from the duodenum drains into the hepatic portal vein
When do duodenal ulcers cause peritonitis, which organs can become inflamed, and why can life-threatening hemorrhage occur?
1) Duodenal ulcers (peptic ulcers) are inflammatory erosions of the duodenal mucosa. Occasionally, an ulcer perforates the duodenal wall, permitting the contents to enter the peritoneal cavity and causing peritonitis
2) Because the superior part of the duodenum closely relates to the liver, gallbladder, and pancreas, any of these structures may become adherent to the inflamed duodenum
3) Although bleeding from duodenal ulcers commonly occurs, erosion of the gastroduodenal artery (a posterior relation of the superior part of the duodenum) by a duodenal ulcer results in severe hemorrhage into the peritoneal cavity and subsequent peritonitis
What is the main function of celiac lymph nodes that surround the celiac trunk?
Celiac lymph nodes that surround the celiac trunk are primary sites of lymph drainage from the foregut-derived viscera
Where do the presynaptic greater splanchnic nerves (T5-T9) pass through and synapse in? What do postsynaptic sympathetic fibers from the celiac ganglion form?
1) The presynaptic greater splanchnic nerves (T5-T9), which pass through the corresponding segmental paravertebral ganglia of the sympathetic trunks, synapse in the prevertebral celiac ganglion
2) Postsynaptic sympathetic fibers from the celiac ganglion form periarterial plexuses on the aforementioned branches of the celiac trunk to innervate the foregut-derived viscera
Where do visceral afferent fibers from the DRG at T5-T9 travel to? What do these fibers join?
1) Visceral afferent fibers from the DRG at T5-T9 use the white communicating rami to join the greater splanchnic nerves en route to the celiac ganglion
2) The afferent fibers join the postsynaptic fibers in the periarterial plexuses
What type of sensation do the visceral afferent fibers convey? What other nerves come from these DRG and what type of sensation do they convey?
1) The visceral afferent fibers convey visceral pain sensations from the foregut derivatives to the DRG at T5-T9
2) These DRG also receive pain sensations conveyed by the somatic sensory fibers of spinal nerves T5-T9
How do somatic pain and visceral pain travel together in the epigastric and foregut derived region?
Somatic pain, originating from the regional parietal peritoneum of the epigastric region or from cutaneous sensory fibers of the epigastric region, and visceral pain from the foregut derivatives are relayed together by the DRG at T5-T9 into the CNS
In the CNS, how is visceral pain from the foregut derivatives perceived as? How is somatic pain arising in the epigastric region consciously perceived as?
1) In the CNS, visceral pain from the foregut derivatives is consciously perceived as referred pain, i.e., dull, diffuse pain sensations felt in the epigastric region of the anterior abdominal wall
2) Somatic pain arising in the epigastric region is consciously perceived as sharp, localized pain
Why is visceral pain from duodenal or gastric ulcers consciously perceived in the epigastric region? (Not sure about this)
Visceral pain from duodenal or gastric ulcers comes from visceral afferent fibers to the DRG at T5-T9, which refers dull diffuse pain to the epigastric region
What do the vagus nerves contribute branches to in relation to foregut derivatives?
The vagus nerve contributes branches to the periarterial plexuses that supply the foregut derivatives (visceral motor functions will be studied later)
