Physiology Lecture 6: Liver

The liver is the _______ organ in the body

Largest

What are the four lobes of the liver?

1. Right

2. Left

3. Quadrate

4. Caudate

What is the inferior, concave aspect of the liver?

Porta hepatis

What is in the porta hepatis?

1. Portal vein (in)

2. R + L hepatic arteries (in)

3. R + L hepatic ducts (out)

What are the primary functional cells of the liver?

Hepatocytes (Parenchymal)

What are the functions of hepatocytes?

1. Form bile

2. Produce cholesterol

3. Synthesize blood components

4. Store nutrients

5. Detoxification

What is the liver encapsulated by?

Glisson capsule

What is the only area of the liver that is not encapsulated?

Porta hepatis

Inside the organ, connective tissue is _____

Sparse

What area of the liver is blood supply from?

Porta hepatis

What are the vessels that provide blood to the liver?

1. R + L Arteries (25%)

2. Portal Vein (75%)

Which vessel provides oxygenated blood to the liver?

R + L Arteries

Which vessel provides partially oxygenated blood with nutrients and hemoglobin?

Portal Vein

Where does blood drainage occur in the liver and to where?

Hepatic veins --> Inferior vena cava

Where does bile drainage occur in the liver and to where?

R + L hepatic ducts --> Cystic duct (storage) and common bile duct (digestion)

What are the hexagon-shaped structures formed by hepatocytes in the liver?

Classical Lobules

What occupies the center in the classical lobules?

Central Vein (initial branch of hepatic veins)

What radiates from the central vein and what do they form?

Hepatocytes, Fenestrated cellular plates

What is located at the vertices of classical lobules?

Portal Triads

What are the components of portal triads?

1. Hepatic artery

2. Portal vein

3. Bile duct

What is the portal triad surrounded by?

1. Space of Moll (Narrow Space)

2. Limiting Plate (Sleeve of hepatocytes)

How much of the lymph formed in the body is from lymphs of the liver?

50%

What are the blood capillaries with large fenestrations between hepatocyte plates in the liver?

Sinusoids

What is the space between hepatocytes and sinusoids where plasma enters?

Space of Disse

What are the small intracellular spaces between hepatocytes that collect bile?

Bile canaliculi

What is the functional advantages of the liver structure?

1. Increased blood flow

2. Low vascular resistance and blood pressure in sinusoids

What is the advantage of low vascular resistance and low blood pressure gradient in sinusoids?

Slow blood movement helps with supply and cleansing of blood components

Where is extra blood stored in the liver?

Blood reservoir

What are the perisinusoidal cells of the liver?

1. Stellate cells

2. Kupffer cells

What are the functions of Stellate cells in the liver?

1. Store vitamins

2. Liver regeneration

What are the functions of Kupffer cells in the liver?

Phagocytosis

What are the three types of liver lobules?

1. Classic

2. Portal

3. Hepatic acinus

Which liver lobule is related to blood?

Classic

Which liver lobule has bile flow towards its bile duct?

Portal

What determines the zones of the hepatic acinus lobule?

Oxygenation levels

Rank the hepatic acinus zones by oxygenation level

1. Zone 1

2. Zone 2

3. Zone 3

What is the role of the liver and gallbladder in food digestion?

Liver - Produce bile

Gallbladder - Store/concentrate bile

What are the parts of the gallbladder?

1. Body

2. Single opening

3. Cystic duct

What does the R and L hepatic ducts lead to?

Common Hepatic duct

What does the hepatic duct and cystic duct lead to?

Common bile duct

What does the common bile duct and pancreatic duct lead to?

Papilla of Vater

What are the muscles that control the opening of common bile duct and pancreatic duct?

Sphincter of Oddi

What are the components of Bile?

1. Water

2. Bilirubin and Cholesterol

3. Bile salts

4. Ions

Is bile secreted continually?

Yes

What is absorbed during concentration of bile in the gallbladder?

1. Water

2. Na+

3. Cl-

4. Bicarbonate

What are the functions of bile?

1. Contain bile acids

2. Excrete waste products from blood

What are the functions of bile acids?

1. Emulsify large fat particles

2. Absorb digested fat end products

What are the stages of bile secretion?

1. Initial Secretion

2. Bile Conditioning

What are is secreted during the initial secretion of bile?

1. Bile acids

2. Cholesterol

What is added during bile conditioning for acid neutralization and by what?

Bicarbonate, secretin

What are the active components of bile?

1. Bile salts

2. Lecithin (Phosphatidylcholine)

What is the circulation of bile salts that lead to re-secretion?

Enterohepatic Circulation

When does the gallbladder empty?

30 mins after a meal (Food reaches duodenum)

What are the mechanisms for gallbladder emptying?

1. Contract gallbladder wall

2. Relax sphincter of Oddi

What is the major stimulus for gallbladder emptying?

CCK

What is the minor stimulus for gallbladder emptying?

ACH

What are the causes of gallstones?

1. Too much water absorption

2. Too much bile absorption

3. Too much cholesterol

4. Inflammation

What are most (80%) gallstones made of?

Cholesterol

What is responsible for the yellow color of bruises and jaundice?

Bilirubin

What is bilirubin bound to in order to reach the liver?

Plasma Albumin

What is responsible for the yellow color of urine?

Urobilin

What is responsible for the brown color of human feces?

Stercobilin

What is caused by the excess of biliribin in plasma that tints body tissues?

Jaundice

What causes hemolytic jaundice?

Increased hemolysis of RBCs

What causes obstructive jaundice?

1. Obstructed bile ducts

2. Liver disease

What is jaundice in neonates caused by?

Immature liver of baby

What are the metabolic fuels stored by the liver?

1. Glycogen (Glucose)

2. Triglycerides (Lipids)

What are the vitamins stored in the liver?

A, D, E, K, B12

What is the only non-fat soluble vitamin stored in the liver?

B12

What are the elements stored in the liver?

1. Iron

2. Copper

3. Trace elements

What are the phases of toxin detoxification in the liver?

1. Functionalization

2. Conjugation

What is the function of the Functionalization phase of toxin detoxification?

Make molecules more water-soluble

What is the function of the Conjugation phase of toxin detoxification?

Increase water solubility and block toxicity

What are the pathways of conjugated toxins from hepatocytes in detoxification?

Bile --> Intestine --> Feces

Blood --> Kidney --> Urine

What are the factors affecting detoxification in the liver?

1. Genetics

2. Liver health

3. Nutrition

4. Gender and Age

5. Medication characteristics

What are the types of Drug-induced liver injury (DILI)?

1. Intrinsic

2. Idiosyncratic (Rare)

What are the common drugs involved with intrinsic DILI?

1. Acetaminophen (APAP)

2. Chemotherapy drugs

What are the common drugs involved with idiosyncratic DILI?

Antibiotics

What is the clinical feature of intrinsic DILI?

Acute liver failure

What is the idea of liver hepatostat?

Optimal liver to body weight ratio must be maintained for optimal metabolism

When do hepatocytes have increased ability to regenerate?

After significant hepatic tissue loss

What happens after up to 70% of the liver is removed?

Organ enlargement until back to original size

During Hepatocyte division and growth, where is hepatocyte growth factor (HGF) high in?

Blood

What produces HGF?

Kupffer cells

What conditions cause severe impairment of liver regeneration?

1. Fibrosis (cirrhosis)

2. Inflammation

3. Viral infections