TBL18 - Liver

Question 1

What does the falciform ligament separate and what does this form? Where is the subphrenic recess located? What is the recess an extension of?

Answer 1

1) The falciform ligament separates the right and left hepatic lobes, which form the convex diaphragmatic surface of the liver
2) The subphrenic recess is located between the diaphragm and anterior and superior aspects of the right (and left) hepatic lobes
3) The recess is a superior extension of the greater sac

Question 2

What is the subhepatic space? What is the hepatorenal recess? Where does fluid in the supracolic compartment drain into when a person is in the supine position?

Answer 2

1) The portion of the supracolic compartment inferior to the visceral (inferior) surface of the liver is called the subhepatic space
2) The hepatorenal recess between the right hepatic lobe and right kidney is an extension of the subhepatic space
3) In the supine position, fluid in the supracolic compartment drains into the hepatorenal recess

Question 3

What are accessory parts of the large right hepatic lobe? What are the visceral surfaces of these accessory parts associated with?

Answer 3

1) The caudate and quadrate lobes are accessory parts of the large right hepatic lobe
2) Visceral surfaces of the caudate and quadrate lobes are associated with the IVC and gallbladder, respectively

Question 4

What does the lesser omentum’s free border form? What does it convey?

Answer 4

1) The lesser omentum’s free border forms the hepatoduodenal ligament
2) It conveys the bile duct, proper hepatic artery, and hepatic portal vein to the liver

Question 5

What is the proper hepatic artery a terminal branch of? What does the proper hepatic artery bifurcate into?

Answer 5

1) The proper hepatic artery is a terminal branch of the common hepatic artery
2) The proper hepatic artery bifurcates into the right and left hepatic arteries that enter the lobes of the liver with the right and left hepatic ducts

Question 6

Why would clamping the omental foramen’s anterior border (the Pringle maneuver) rapidly control hepatic hemorrhaging during emergency surgery?

Answer 6

1) The Pringle manoeuvre is a surgical manoeuvre used in some abdominal operations
2) A large atraumatic haemostat is used to clamp the hepatoduodenal ligament (free border of the lesser omentum) interrupting the flow of blood through the hepatic artery and the portal vein and thus helping to control bleeding from the liver
3) More commonly, in the absence of soft clamp, manual compression of the hepaticoduodenal ligament is performed

Question 7

How is the liver commonly palpated? How do increases in central venous pressure or metastatic carcinomas from the large intestine cause hepatomegaly and where is the liver palpated under these conditions?

Answer 7

1) The liver may be palpated in a supine person because of the inferior movement of the diaphragm and liver that accompanies deep inspiration. 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
2) The liver is a soft, highly vascular organ that receives a large amount of blood immediately before it enters the heart. Any rise in central venous pressure is directly transmitted to the liver, which enlarges as it becomes engorged with blood
3) 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
4) The liver is a common site of metastatic carcinoma (secondary cancers spreading from organs drained by the portal system of the veins). Cancer cells also pass to the liver from the thorax, especially from the right breast, because of the communications between thoracic lymph nodes and the lymphatic vessels draining the bare area of the liver. Metastatic tumors form hard, rounded nodules within the hepatic parenchyma

Question 8

What is the pathogenesis of cirrhosis of the liver and why does it cause portal hypertension? Why is metabolic evidence of liver failure late to appear?

Answer 8

1) There is progressive destruction of hepatocytes in hepatic cirrhosis and replacement of these cells by fat and fibrous tissue
2) Alcoholic cirrhosis, the most common of many causes of portal hypertension, is characterized by hepatomegaly and a “hobnail” appearance of the liver surface resulting from fatty changes and fibrosis
2) Fibrous tissue surrounds the intrahepatic blood vessels and biliary ducts, making the liver firm, and impeding the circulation of blood through it (portal hypertension)
3) The liver has great functional reserve; therefore the metabolic evidence of liver failure is late to appear

Question 9

How is a liver biopsy properly obtained?

Answer 9

1) Because the liver is located in the right hypochondriac region where it receives protection from the overlying thoracic cage, the needle is commonly directed through the right 10th intercostal space in the midaxillary line
2) Before the physician takes the biopsy, the person is asked to hold his or her breath in full expiration to reduce the costodiaphragmatic recess and to lessen the possibility of damaging the lung and contaminating the pleural cavity

Question 10

Where does the subcutaneous paraumbilical vein originate near and what is it a tributary of?

Answer 10

The subcutaneous paraumbilical vein, which originates near the umbilicus, is a tributary of the hepatic portal vein

Question 11

Where does the paraumbilical vein travel? What does it join and where?

Answer 11

1) Inferior to the sternal xiphoid process, the paraumbilical vein pierces the linea alba and parietal peritoneum to enter the falciform ligament
2) The vein courses in the inferior border of the falciform ligament to join the portal vein

Question 12

What is the pathogenesis of caput medusa?

Answer 12

1) In severe cases of portal obstruction, the veins of the anterior abdominal wall (normally caval tributaries) that anastomose with the para-umbilical vein (normally portal tributaries) may become varicose and look somewhat like small snakes radiating under the skin around the umbilicus
2) 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 13

Why does a portacaval anastomosis or a splenorenal shunt surgically reduce portal hypertension?

Answer 13

1) 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
2) This portocaval anastomosis or portosystemic shunt may be done where these vessels lie close to each other posterior to the liver
3) Another way of reducing portal pressure is to join the splenic vein to the left renal vein, after splenectomy (splenorenal anastomosis or shunt)

Question 14

Where is lymph from the liver filtered first before reaching the thoracic duct? How much of the lymph entering the thoracic duct originates in the liver?

Answer 14

1) Before reaching the thoracic duct, lymph from the liver is serially filtered by hepatic lymph nodes in the hepatoduodenal ligament and the celiac lymph nodes around the celiac trunk
2) Nearly half of the lymph entering the thoracic duct originates in the liver

Question 15

What forms portal triads and where do these branches course? Use top right LM image, pp. 315 to distinguish the structures within the portal triads.

Answer 15

1) Branches of the hepatic portal vein, proper hepatic artery, and hepatic ducts form portal triads as they course together throughout the liver stroma
2) Look at LM image

Question 16

What do the portal triads form around the peripheral margins of the polyhedral hepatic lobules? How are hepatocytes separated within the lobules?

Answer 16

1) The portal triads form an incomplete ring around peripheral margins of the polyhedral hepatic lobules, which create subunits of the hepatic lobes
2) Within the lobules, rows of hepatocytes are separated by the hepatic sinusoids (not labeled) that terminate in the central veins

Question 17

How does blood travel from the vessels of the portal triads? Where do central veins drain into? Where do the right and left hepatic veins empty into?

Answer 17

1) Blood flows from vessels of the portal triads into the sinusoids and drains into the central veins
2) Central veins drain into tributaries of the hepatic veins (ignore sublobular vein)
3) The right and left hepatic veins empty into the IVC

Question 18

What are sinusoids separated from adjacent rows of hepatocytes by? What type of tissue is found within this structure and what function does this tissue serve?

Answer 18

1) The sinusoids are separated from adjacent rows of hepatocytes by the narrow space of Disse
2) Loose connective tissue, which occupies the space of Disse, suspends the sinusoids between the rows of hepatocytes

Question 19

What are clefts between endothelial cells lining the sinusoids partially filled with? What traverses the clefts into the space of Disse? What do Kupffer cells do?

Answer 19

1) Clefts between endothelial cells lining the sinusoids are partially filled by macrophages designated Kupffer cells
2) Small plasma proteins traverse the clefts into the space of Disse
3) Kupffer cells remove blood-borne bacteria, viruses, and parasites

Question 20

Where are secretory products from the hepatocytes released into and where do they travel? Define the function of fat-containing cells (of Ito), which are normal residents of the space of Disse.

Answer 20

1) Secretory products from the hepatocytes (e.g., plasma proteins and glucose) are released into the space of Disse and rapidly traverse the endothelial clefts of the sinusoids to enter the bloodstream
2) In a normal liver, Hepatic stellate cells store and regulate transport of 80% of total retinoids (vitamin A) the body via large lipid droplets that are abundant in their cytoplasms

Question 21

Why is hepatic lymph, which originates in the space of Disse, so voluminous?

Answer 21

1) Approximately half of the lymph formed in the body is formed in the liver. Due to the large pores or fenestrations in sinusoidal endothelial cells, fluid and proteins in blood flow freely into the space between the endothelium and hepatocytes (the “space of Disse”), forming lymph. Lymph flows through the space of Disse to collect in small lymphatic capillaries associated with portal triads, and from there in the systemic lymphatic system
2) As you might expect, if pressure in the sinusoids increases much above normal, there is a corresponding increase in the rate of lymph production

Question 22

Why is excessive alcohol consumption toxic to the liver?

Answer 22

1) Excessive ethanol consumption is toxic to the liver and may cause morphologic changes and clinical symptoms including liver cell damage, extensive fibrosis, and inflammation
2) Hepatocytes in the alcoholic liver accumulate large amounts of fat and often become distended beyond recognition

Question 23

What do the cell membranes of adjoining hepatocytes form? At what rate do hepatocytes secrete bile into the canaliculi?

Answer 23

1) The cell membranes of adjoining hepatocytes form tiny bile canaliculi that convey bile to the biliary ducts of the portal triads
2) Hepatocytes secrete bile (essential for fat digestion) into the canaliculi at a rate of 30 ml/hr

Question 24

What do tight junctions link together within the liver and what function does this serve? What other cells do tight junctions unite within the biliary duct system?

Answer 24

1) Tight junctions link the cell membranes of adjacent hepatocytes to prevent bile leakage from the canaliculi
2) Tight junctions also unite cells of the simple cuboidal epithelium that lines the biliary duct system

Question 25

Why does intrahepatic cholestasis cause jaundice?

Answer 25

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

Question 26

What is the liver acinus?

Answer 26

The liver acinus, another concept of liver lobulation, is an oval-shaped area of parenchyma defined by its blood supply from the vessels of the portal triad that forms the short axis of the acinus

Question 27

What is the short axis of the liver acinus surrounded by? Define the functional and pathological relevance of the zones.

Answer 27

1) The short axis is surrounded by three concentric, elliptical zones (acinar zones 1, 2, and 3)
2) Zone 1 receives oxygen, hormones, and nutrients from the bloodstream, and most glycogen and plasma protein synthesis by hepatocytes occurs here
3) Zone 3 is poorly oxygenated, is the first to show ischemic necrosis and fat accumulation if metabolism is altered, and is the site of most drug and alcohol detoxification
4) Zone 2 is an intermediate zone