Block 7 (GI) - L7 to L8 Flashcards
Oxygenated blood is supplied to the liver via the ___.
Hepatic artery only
Describe the hepatic circulation.
The heart pumps oxygenated blood through the hepatic artery to the liver. In addition, the splenic vein and superior mesenteric vein combine to form the hepatic portal vein, which goes to the liver. Blood is drained to the hepatic veins and to IVC.
What is a lobule?
Hexagonal building block of the liver parenchyma with a portal tract at each apex
What makes up the portal tract?
Hepatic artery, portal vein, bile duct
Blood flows ___ the central vein; bile flows ___ the central vein.
Toward; away from
___ are arranged in linear cords from the periphery to the central vein.
Hepatocytes
What are periportal hepatocytes?
First to receive blood and to regenerate, last to undergo necrosis
What are centrilobular hepatocytes?
Most susceptible to ischemic insults
What are sinusoids?
Capillary network through the liver that converts nutrient rich portal venous and highly-oxygenated arterial blood past the hepatocytes
What are Kupffer cells?
Macrophage cells of the liver
Describe the endothelium of the liver.
Fenestrated to allow passage of nutrients and lipids from portal blood to the hepatocyte
What is the Space of Disse and what does it contained?
Loosely arranged ECM containing stellate cells, NK cells, and T/B cells.
How is the surface area increased in hepatocytes?
Microvilli
What are 2 of the metabolic functions of hepatocytes?
Glucose and lipid metabolism
What are 2 proteins synthesized in the liver?
Albumin and coagulation factors (except 8)
What 5 things are stored in the liver?
Glycogen, triglycerides, iron, copper, lipid soluble vitamins
What are 3 of the catabolic functions of the hepatocytes?
- Converting ammonia to urea
- Catabolizing certain proteins and hormones
- Detoxifying drugs and chemicals
What is one excretory function of the liver?
Bile excretion
What is hepatic encephalopathy and what does it require?
Reversible neuropsychiatric abnormalities seen in patients with liver failure; requires the presence of portal HTN
How does hepatic encephalopathy develop?
Normally, the liver clears portal vein ammonia, converting it to glutamine and urea, but it remains in the blood, where it becomes neurotoxic at elevated concentrations
How are liver injury tests classified by type?
- Hepatocellular (ALT/AST elevation)
2. Cholestatic (Alk Phos/T.bili elevation)
How are liver injury tests classified by duration?
- Acute: abrupt onset, <6 months but usually <1 month
2. Chronic >6 months
How are liver injury tests classified by magnitude?
- Mild (AST/ALT elevations <200)
- Moderate (200-600)
- Severe (>600)
Which serum transaminase is more specific for hepatocyte damage?
ALT (alanine aminotransferase)
AST (aspartate) can be found in parts of the body
What are causes of markedly elevated aminotransferase levels (>1,000 U/L)?
- Drug/toxin-induced injury (tylenol, NOT alcohol alone)
- Acute viral hepatitis
- Shock liver
- Autoimmune hepatitis
- Common bile duct stone
What is cholestasis?
Any condition in which substances normally excreted into the bile are retained
Decrease in bile flow due to impaired secretion/formation by hepatocytes OR to obstruction of bile flow through intra- or extra-hepatic ducts
How does cholestasis appear histologically?
Bile within the hepatocytes and canalictular spaces; often with associated cell injury
What are 4 markers of cholestasis?
- Alkaline phosphatase
- Gamma glutamyl transferase (GGT)
- 5’-nucleotidase
- Bilirubin
Where is alkaline phosphatase located in the liver?
Microvilli of the bile canaliculus
What happens to alkaline phosphatase in cholestasis?
Increases (sensitive indicator of obstructive and space-occupying lesions of the liver)
What induces gamma glutamyl transferase (GGT)?
Alcohol and medication
What causes bilirubin to increase?
With extensive biliary obstruction or diffuse hepatic cell disruption as a result of cholestasis
What are liver function tests and what do they reflect?
Albumin, PT/INR, serum bilirbuin
The liver’s synthetic or excretory capactiy
What is the most abundant blood protein?
Albumin
What happens to albumin in acute and chronic liver disease?
- Preserved in acute liver disease
2. Low due to cirrhosis in the setting of chronic liver disease
What does PT/INR indicate regarding the liver?
Clotting factors that are synthesized by the liver in a vitamin-K dependent fashion; helpful in the diagnosis of hepatic dysfunction
What does serum bilirubin reflect?
The ability of the hepatocyte to secrete bilirubin into the bile canaliculus; can be elevated in hepatocellular injury or cholestatic injury
In both hepatocellular and cholestatic injury, the ___ fraction predominates.
Direct (conjugated)
What are the three broad forms of hepatic dysfunction?
- Acute hepatitis
- Acute liver failure (fulminant liver failure)
- Chronic hepatitis
What is acute liver injury?
Hepatic dysfunction without encephalopathy
What are 5 pathologic findings seen in acute hepatitis?
- Ballooning degeneration
- Apoptosis
- Necrosis
- Inflammation
- Cholestasis
What is ballooning degeneration and what is it associated with?
Swollen liver cells with lots of debris int he cytoplasm
NASH, alcohol, acute hepatitis
What is acute liver failure?
Sudden loss of hepatic function in a person without evidence of preexisting liver disease
What is the clinical definition of acute liver failure?
Coagulopathy (INR >1.5) and any degree of hepatic encephalopathy both occurring within 24 weeks of the first onset of symptoms in patients without underlying liver disease
What are exceptions to the definition of acute liver failure?
Wilson’s disease, vertically-acquired HBV, and autoimmune hepatitis
What are causes of acute liver failure?
- Hepatitis A or B
- Drugs and chemical toxicity
- Autoimmune hepatitis
- Wilson’s disease
- Budd-Chiari
- Rare (ischemia, malignancy)
- Unknown (15%)
What is seen on histology in acute liver failure?
Massive hepatic necrosis
What are causes of chronic hepatitis?
- Hepatitis B, C, or D
- Autoimmune hepatitis
- Drugs
- Wilson’s disease
- Alpha-1 antitrypsin deficiency
- Hemochromatosis
- NASH
- Alcohol
What is seen on histology in chronic hepatitis?
Lack of balloon cells and fibrosis
What role do stellate cells play in chronic hepatitis?
Deposit collagen, leading to fibrosis
How is chronic hepatitis characterized?
- Grade (how bad the inflammation is)
2. Stage (how much fibrosis there is)
What are the 4 stages of fibrosis in chronic hepatitis?
- Portal
- Periportal
- Bridging
- Cirrhosis