TBL 27

Question 1

Discuss where the liver bud is derived from.

Answer 1

liver bud is an endodermal outgrowth from the 2nd part of the duodenum that marks the end of its foregut-derived portion.

Question 2

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Answer 2

liver bud forms the bile duct (unlabeled) that terminally bifurcates into the right and left hepatic ducts

Question 3

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Answer 3

proliferating cells from the hepatic ducts grow into the septum transversum and differentiate into hepatocytes (liver parenchymal cells)

Question 4

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Answer 4

mesenchymal cells of the septum transversum form the liver stroma.

Question 5

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Answer 5

vitelline veins pass through the septum transversum enroute to the sinus venosus.

Question 6

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Answer 6

vitelline veins form the hepatic sinusoids and the bilateral hepatic veins among the proliferating hepatocytes in the septum transversum.

Question 7

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Answer 7

embryonic left-to-right venous shunt, and envision the enlarged right vitelline vein forms the SMV that joins the splenic vein to form the hepatic portal vein.

Question 8

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Answer 8

venous blood from the entire GI tract and the spleen drains into the hepatic portal vein; thus, it provides 80% of the blood flow to the liver.

Question 9

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Answer 9

endodermal outgrowth from the proximal bile duct forms the cystic duct (unlabeled) and cells proliferating from it form the gallbladder.

Question 10

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Answer 10

dorsal mesogastrium of the stomach is part of the dorsal mesentery that suspends the entire gut tube from the posterior abdominal wall.

Question 11

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Answer 11

ventral mesentery is formed by the septum transversum (unlabeled brownish segment) and suspends the abdominal esophagus, stomach, and proximal duodenum from the anterior abdominal wall.

Question 12

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Answer 12

progressive growth of the liver divides the ventral mesentery into the lesser omentum and falciform ligament.

Question 13

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Answer 13

endodermal outgrowths from the duodenum adjacent to the bile duct form the dorsal and ventral pancreatic buds.

Question 14

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Answer 14

large dorsal pancreatic bud grows into the dorsal mesentery and the small ventral bud remains close to the bile duct.

Question 15

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Answer 15

rotation of the stomach around its anteroposterior axis creates the C-shaped curve of the duodenum.

the rotation moves the ventral pancreatic bud into the dorsal mesentery where it joins the dorsal pancreatic bud.

Question 16

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Answer 16

mesenchymal cells of the mesentery form the stroma of the pancreas.

Question 17

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Answer 17

like the spleen, the pancreatic primordium resides in the dorsal mesogastrium.

Question 18

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Answer 18

stomach rotations pull the dorsal mesogastrium to the left where its partial fusion with the parietal peritoneum on the posterior abdominal wall places the developing pancreas in a retroperitoneal position.

Question 19

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Answer 19

main pancreatic duct transports secretions (e.g., digestive enzymes) from the pancreatic parenchymal cells into the bile duct.

Question 20

How is an annular pancreas formed and when does it induce vomiting that contains bile? What creates its characteristic “double bubble” radiographic sign?

Answer 20

The right portion of the ventral bud migrates along its normal route. The left portion of the ventral bud migrates in the opposite direction and now the duodenum is surrounded by pancreatic tissue- forming a pancreatic ring around the descending portion of the duodenum.

If the annular pancreas lies distal to the major duodenal papilla the induced vomiting will contain bile.

Double bubble- In symptomatic neonates, a plain abdominal radiograph will show the classic “double bubble” sign with air in the stomach and duodenum.

Note: Normally the two components of the ventral pancreatic bud fuse and rotate around the duodenum so they come to lie below the dorsal pancreatic bud.

Question 21

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Answer 21

liver abuts the diaphragm

Question 22

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Answer 22

falciform ligament separates the right and left hepatic lobes, which form the convex diaphragmatic surface of the liver.

Question 23

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Answer 23

subphrenic recess is the superior extension of the supracolic compartment of the greater sac, and the subhepatic space is the portion of the supracolic compartment below the inferior surface of the liver.

Question 24

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Answer 24

subhepatic space extends as the hepatorenal recess between the right lobe of the liver and the right kidney.

Question 25

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Answer 25

in the supine position, ascites fluid from the supracolic compartment and/or lesser sac drains into the hepatorenal recess.

Question 26

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Answer 26

caudate and quadrate lobes are accessory parts of the large right hepatic lobe on its inferior surface.

Question 27

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Answer 27

caudate lobe is associated with the IVC and the quadrate lobe is associated with the gallbladder.

Question 28

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Answer 28

the free border of the lesser omentum forms the hepatoduodenal ligament that conveys the bile duct, proper hepatic artery, and hepatic portal vein to the liver.

Question 29

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Answer 29

proper hepatic artery bifurcates into the right and left hepatic arteries that follow the right and left hepatic ducts to the lobes of the liver.

Question 30

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Answer 30

subcutaneous paraumbilical umbilical vein originates near the umbilicus and drains into the hepatic portal vein.

Question 31

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Answer 31

the paraumbilical vein courses within the superficial fascia toward the xiphoid process of the sternum

Question 32

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Answer 32

near the xiphoid process it pierces the linea alba and extraperitoneal fat to enter the falciform ligament (unlabeled) enroute to the hepatic portal vein.

Question 33

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Answer 33

paraumbilical vein courses within the inferior border of the falciform ligament.

Question 34

How is the normal liver palpated? Where is it palpated after hepatomegaly results from an increase in central venous pressure or a metastatic carcinoma from the large intestine?

Answer 34

One method of palpating the liver is to place the left hand posteriorly behind the lower rib cage. Then, put the right hand on the person’s right upper quadrant, lateral to the rectus abdominis and inferior to the costal margin. The person is asked to take a deep breath as the examiner presses posterosuperiorly with the right hand and pulls anteriorly with the left hand.

When the liver is massively enlarged, its inferior edge may be readily palpated below the right costal margin and may even reach the pelvic brim in the right lower quadrant of the abdomen.

Question 35

Why does clamping the omental foramen’s anterior border (i.e., the Pringle maneuver) rapidly control hepatic hemorrhaging during emergency surgery?

Answer 35

The hepatoduodenal ligament is being clamped which would compress the structures of the portal triad (portal vein, hepatic artery, and bile duct).

Question 36

What is the pathogenesis of caput medusa?

Answer 36

In severe cases of portal obstruction, the veins of the anterior abdominal wall (normally caval tributaries) that anastomose with the para-umbilical veins (normally portal tributaries) may become varicose and look somewhat like small snakes radiating under the skin around the umbilicus.

This condition is referred to as caput medusae because of its resemblance to the serpents on the head of Medusa, a character in Greek mythology

Question 37

Why can a surgical portacaval anastomosis or a splenorenal shunt reduce portal hypertension?

Answer 37

A common method for reducing portal hypertension
is to divert blood from the portal venous system to the
systemic venous system by creating a communication
between the hepatic portal vein and the IVC.

This portocaval anastomosis or portosystemic shunt may be done where these vessels lie close to each other posterior to the liver.

Another way of reducing portal pressure is to join the splenic vein to the left renal vein, after splenectomy (splenorenal anastomosis or shunt)

Question 38

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Answer 38

lymph from the liver is serially filtered by the hepatic lymph nodes in the hepatoduodenal ligament and celiac lymph nodes around the celiac trunk before entering the thoracic duct.

half of the lymph entering the thoracic duct is from the liver.

Question 39

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Answer 39

hepatic portal vein, proper hepatic artery, and hepatic duct form portal triads in the liver stroma.

the triads course along the peripheral edges of polyhedral hepatic lobules, which have the central veins as their morphologic axes.

Question 40

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Answer 40

blood flows from the hepatic artery and portal vein through the hepatic sinusoids into the central veins.

central veins drain into tributaries of the hepatic veins

bilateral hepatic veins drain blood from the liver into the IVC.

Question 41

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Answer 41

hepatic sinusoids are separated from the adjacent rows of hepatocytes by the narrow space of Disse (i.e., loose connective tissue that suspends the sinusoids between the hepatocytic rows).

Question 42

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Answer 42

clefts between endothelial cells of the sinusoids are partially filled by Kupffer cells (macrophages) that phagocytize blood-borne bacteria, viruses, and parasites.

Question 43

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Answer 43

secretory products of the hepatocytes (e.g., plasma proteins and glucose) that are released into the space of Disse easily traverse the endothelial clefts into the sinusoids.

Question 44

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Answer 44

hepatocytes also secrete bile, which is essential for fat digestion, into tiny bile canaliculi for transport into the biliary ducts of the portal triads.

canaliculi are formed by the cell membranes of adjoining hepatocytes.

Question 45

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Answer 45

tight junctions link the cell membranes of the canaliculi to prevent the leakage of bile.

Question 46

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Answer 46

endoderm-derived simple cuboidal cells that line the biliary ducts, hepatic ducts, bile duct, and cystic duct are also united by tight junctions.

Question 47

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Answer 47

liver acinus is an oval-shaped area of parenchyma defined by the blood supply from the portal triad that forms its short axis.

Question 48

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Answer 48

three concentric, elliptical zones (acinar zones 1, 2, and 3) surrounding the short axis.

Question 49

What is the function of hepatic stellate cells in the space of Disse?

Answer 49

Hepatic stellate cells (formerly known as Sternzellen, Ito cells, fat storing cells, or lipocytes) are star-shaped cells in the perisinusoidal space of Dissé between hepatocytes and endothelium of hepatic sinusoids.

In a normal liver, they store and regulate transport
of 80% of total retinoids (vitamin A) in the body via large lipid droplets that are abundant in their cytoplasms.

Stellate cells also contain alphasmooth smooth muscle actin, which via contraction in response to vasoactive substances may regulate blood flow in the sinusoids.

Note: Many acute and chronic diseases of liver activate transformation of quiescent stellate cells into myofibroblast-like cells that engage in the inflammatory fibrotic response by undergoing mitosis and synthesizing
and secreting increased amounts of ECM consisting of collagen (types I, III, and IV), laminin, fibronectin, and proteoglycans.

Question 50

Why does intrahepatic cholestasis cause jaundice?

Answer 50

Intrahepatic cholestasis is a pathologic state of reduced bile formation or flow. It leads to jaundice, a yellowing of the skin and sclera of the eyes, because of excess circulating bilirubin.

Question 51

Why is acinar zone 3 the first to show ischemic necrosis?

Answer 51

Zone 3 is furthest from the distributing vessels, Zone 3 is poorly oxygenated.

As opposed to Zone 1, most central, is closest to the terminal distributing branches of the portal venule and hepatic arteriole.

Question 52

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Answer 52

cystic artery to the gallbladder arises from the right hepatic artery.

Question 53

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Answer 53

lymph from the gallbladder, like that from the liver, drains into the hepatic and celiac lymph nodes.

Question 54

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Answer 54

fundus of the gallbladder projects from the inferior border of the liver on the right midclavicular line at the edge of the 9th costal cartilage.

Question 55

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Answer 55

observe the close proximity of the duodenum and transverse colon to the gallbladder.

Question 56

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Answer 56

absorption of water across the simple columnar epithelium concentrates bile for luminal storage (up to a 50 ml) and when stored bile distends the lumen, the mucosal folds disappear.

Question 57

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Answer 57

diagonally organized bundles of smooth muscle form the muscularis externa that contracts under the influence of cholecystokinin.

Question 58

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Answer 58

vagus nerve and postsynaptic fibers from the celiac ganglion with accompanying visceral afferent fibers from the DRG at T5-T9 form periarterial plexuses on the branches of the celiac trunk.

Question 59

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Answer 59

sympathetic-mediated vasoconstriction regulates blood flow to the gallbladder and liver.

Question 60

What causes biliary colic and how could it lead to cholecystitis? How is pain perceived after blockage of the cystic duct?

Answer 60

A stone lodged in the cystic duct
causes biliary colic (intense, spasmodic pain).

When the gallbladder relaxes, the stone may move back into the gallbladder. If the stone blocks the cystic duct, cholecystitis (inflammation of the gallbladder) occurs because of bile accumulation, causing enlargement of the gallbladder.

Pain from an impaction of the gallbladder develops in the
epigastric region and later shifts to the right hypochondriac region at the junction of the 9th costal cartilage and the lateral border of the rectus sheath.

• post thoracic wall or right shoulder.

Question 61

Why does a cholecystoenteric fistula involve the 1st part of the duodenum or transverse colon and what is its diagnostic radiographic sign?

Answer 61

Because of their proximity to the gallbladder,
the superior part of the duodenum and the transverse colon are most likely to develop a fistula of this type.

A cholecysto-enteric fi stula also permits gas
from the gastrointestinal tract to enter the gallbladder, providing a diagnostic radiographic sign.

Note: A gallbladder that is dilated and inflamed owing
to an impacted gallstone in its duct may develop
adhesions with adjacent viscera. Continued inflammation
may break down (ulcerate) the tissue boundaries
between the gallbladder and a part of the gastrointestinal tract adherent to it, resulting in a cholecysto-enteric fistula

Question 62

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Answer 62

retroperitoneal pancreas resides on the posterior abdominal wall adjacent to vertebrae L2 and L3.

The pancreas’ anterior parietal peritoneal covering forms the floor of the lesser sac.

Question 63

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Answer 63

• head of the pancreas: C-curve of duodenum, bile duct, and IVC
• neck of the pancreas: SMA and hepatic portal vein
• body of the pancreas: abdominal aorta and left kidney
• tail of the pancreas: hilum of the spleen

Question 64

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Answer 64

head of the pancreas is supplied by the superior and inferior pancreaticoduodenal arteries and recognize the neck, body, and tail are supplied by the splenic artery.

Question 65

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Answer 65

venous blood from the pancreas drains into the hepatic portal vein.

Question 66

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Answer 66

periarterial plexus to the pancreas includes sympathetic fibers that regulate its blood flow (pancreatic secretion is mainly under hormonal control).

Question 67

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Answer 67

distension or inflammatory irritation of the pancreas activates visceral afferent fibers that elicit dull, diffuse pain in the epigastric region.

Question 68

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Answer 68

distension or irritation of the parietal peritoneum covering the anterior surface of the pancreas activates somatic afferent fibers that trigger sharp, localized back pain.

Question 69

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Answer 69

the union of the main pancreatic duct to the bile duct forms the short, dilated hepatopancreatic ampulla in the wall of the 2nd part of the duodenum.

Question 70

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Answer 70

contraction of the smooth muscle sphincters of the bile duct, pancreatic duct, and hepatopancreatic ampulla limits the flow of bile and pancreatic enzymes into the duodenum.

Question 71

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Answer 71

bile is continuously secreted by the liver and when the smooth muscle sphincters are contracted between meals, bile backs up into the gallbladder for concentration and storage.

Question 72

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Answer 72

cholecystokinin activates both relaxation of the sphincters and contraction of the muscularis externa in the gallbladder.

Question 73

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Answer 73

main pancreatic duct extends from the tail to the head of the pancreas.

Question 74

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Answer 74

surmise the dark stained (serous) cells of the secretory acini secrete digestive enzymes, mainly under the influence of cholecystokinin at a rate of 1-2 L/day, into smaller ducts that empty into the main pancreatic duct.

Question 75

Why can spasms of the hepatopancreatic sphincter or obstruction of the hepatopancreatic ampulla by gallstones cause pancreatitis?

Answer 75

Because the main pancreatic duct joins the bile duct
to form the hepatopancreatic ampulla and pierces
the duodenal wall, a gallstone passing along the
extrahepatic bile passages may lodge in the constricted distal end of the ampulla, where it opens at the summit of the major duodenal papilla. In this case, both the biliary and pancreatic duct systems are blocked and neither bile nor pancreatic juice can enter the duodenum.

However, bile may back up and enter the pancreatic duct, usually resulting in pancreatitis (infl ammation of the pancreas).

Question 76

When does pancreatic cancer cause jaundice and why does the cancer have a high fatality rate?

Answer 76

Because of the posterior relationships of the pancreas,
cancer of the head often compresses and obstructs the bile duct and/or the hepatopancreatic ampulla. This causes obstruction, resulting in the retention of bile pigments, enlargement of the gallbladder, and obstructive jaundice.

The pancreas’s extensive drainage to relatively inaccessible lymph nodes, and the fact that pancreatic cancer typically metastasizes to the liver early, via the hepatic portal vein, make surgical resection of the cancerous pancreas nearly futile.

Question 77

Why can acute pancreatitis become life-threatening?

Answer 77

However, acinar cell injury or pancreatic
duct obstruction may lead to inappropriate extracellular leakage of activated digestive enzymes and autodigestion of pancreatic acini.

Edema and progressive fibrosis of the stroma may ensue and cause hemorrhage and ultimately pancreatic insufficiency.