Liver Flashcards
What is the normal colour of the liver?
Typically a reddish-brown, but may be brown in animals, such as cattle, sheep and pigs, that have been bled out
Why might a liver be yellow-brownish in colour?
Accumulation of fats in the liver can cause it to have a yellowish-brown appearance
Why might a liver be greenish/yellow?
Post-mortem changes can cause areas of pallor or darkening or greenish-yellow discolouration, especially adjacent to the gall bladder
What is the weight of the liver dependent on?
The weight of the liver as a proportion of body wieght can vary depending on factors includin the species (higher in carnoviores comapred to herbivores), nutritional status (hepatic storage of glycogen and fat) and age (liver weight decreases with age).
What is the percentage of body weight of the liver?
Dog = 3-4%
Horse = 1-1.5%
What blood vessels deliver blood to the liver?
Portal vein – provides 70-80% of the blood inflow
Hepatic artery
From which organs does the blood in the portal vein come from?
Collects blood from the spleen, pancreas, stomach and intestines
From what blood vessel does the hepatic artery originate from?
From the ceoliac artery, which arises from the aorta
What blood vessels drain blood from the liver?
Hepatic vein to the caudal vena cava
After blood enters the liver from the portal vein and hepatic artery, what structures for sit flow through before arriving in the hepatic veins?
Portal vein and hepatic artery > hepatic sinusoids > across hepatic lobule > central vein > interlobualr veins > hepatic veins
Within the functional unit, the hepatic acinus, what are the 3 zones?
Zone 1 – periportal region. The area that recievs the blood frm the portal vein and hepatic artery first
Zone 2 – midzonal region. Receives blood next
Zone 3 – centtilobular region. Recives the blood last before it drains into the central vein
What are the metabolic differences between the 3 zones of the hepatic acinus?
Zone 1 – periportal will receive blood with the highest oxygen and nutrient content
Zone 3 – centrilobualr will receive blood with lower oxygen and nutrient content. Hepatocytes in zone 3 also have higher levels of metabolic enzymes. These factors make this zone the most sensitive to injury by toxic compounds
Name 3 circulatory disorders affecting the liver.
- Congenital portosystemic shunts
- Post-hepatic conditions affecting outflow of blood from the liver
- Intra-hepatic or pre-hepatic conditions associated with abnormal portal vein inflow
How can portosystemic shunts be classified?
Whether the anomlous blood vessel is within the liver or not
How does an intra-hepatic portosystemic shunt form?
Large blood vessel connects the portal vein directly to the hepatic vein, which is a lower resistance path than through the lobule and smaller sinusoides, so a significant portion of blood flow is through this shunt and bypasses the functional part of the liver
How does an extrahepatic portosystemic shunt form?
Large blood vessel connect the portal vein/tributaries of the portal vein, bypassing the liver and through extra-hepatic anomalous vein to connect to the systemic circulation (caudal vena cava or hepatic vein).
Distinguish which breeds are affected by which type of portosystemic shunt.
Extrahepatic – small (wEe) dog breeds
Intra-hepatic – large (bIg) dog breeds
Distinguish intra and extrahepatic CPSS.
Intrahepatic CPSS – left or right portal vein branch to hepatic vein or directly with caudal vena cava
Extra-hepatic CPSS – left or right gastric vein or splenic vein to the caudal vena cava or azygous vein
What are the functional consequences of congenital portosystemic shunts?
- Reduced hepatic perfusion
- Small liver due to underperfusion – microhepatica
- Poor growth due to less liver and so less functional capacity
- Hepatic encephalopathy, as the liver is unable to detoxify waste products and these build up and affect the central nervous system
Will congenital portosystemic shunts result in increased blood pressure in the portal venous system – portal hypertension?
No – offer a lower resistance route
How does heart disease affect outflow from the liver?
Especially right sided CHF, which will increase pressure in the caudal vena cava which can be referred back through the hepatic vein to the liver and impair outflow of blood from the liver
How does hepatic vein/vena cava obstruction affect outflow from the liver?
Luminal obstruction (thrombus), vessle wall thickening (neoplasia, inflammation), external compression (by a mass, such as an abscess or tumour)
What are the consequences of impairment of post-hepatic outflow?
- Hepatic passive venous congestion – dilation of the sinusoids and central vein and becoming packed full of the blood, can extend to portal vein
- Hepatomegaly – blood pools and congest in the liver may make it appear larger so there is some degree of hepatomegaly
- Chronic passive congestion may develop an enhanced lobular or reticular pattern on the sectioned surface of the liver (nutmeg liver). Reddening due to congestion and the yellowish colour caused by accumulation of fat, create enhanced lobular pattern
Could post-hepatic conditions causing passive congestion of the liver cause an increased blood pressure in the portal venous system (portal hypertension)?
Yes