Liver Structure and Function Flashcards
What is the largest organ in the body?
The liver which weights about 1.4kg
Where is the liver located within the abdomen?
Upper right quadrant of abdomen (tucked against inferior surface of diaphragm)
How many lobes does the liver contain?
4
What are the 4 lobes of the liver?
Left lobe
Right lobe
Caudate lobe
Quadrate lobe
On what surface is the portal of the liver?
Posterior
Whats enters and exits the liver through the porta?
Blood vessels (hepatic portal vein, hepatic artery)
Lymphatic vessels
Ducts (right/left hepatic ducts forming common hepatic duct)
Nerves (hepatic nerve plexus)
Explain the anastomosis of the common hepatic duct to reach the spincter of Oddi?
Common hepatic duct joined by cystic duct to form common bile duct
Common bile duct joined by pancreatic duct to form major duodenal papilla
What does the coronary ligament attach the liver to?
Inferior surface of diaphragm
What is the liver covered by?
Connective tissue capsule and visceral peritoneum (except for bare area)
Where is the bare area of the liver?
Diaphragmatic surface surrounded by coronary ligament
What does the connective tissue surrounding the liver become at the porta?
Branching network of septa into the body of the liver to give support
What doe vessels, ducts and nerves follow throughout the liver?
Septa
What does the septa divide the liver into?
Hexagonal lobules
What forms the portal triad?
Hepatic portal vein, hepatic artery and hepatic duct
Where are portal triads found?
At each corner of hexagonal lobule (also with nerves and lymph vessels)
What is at the centre of each lobule?
Central veins
What do central veins of lobules go onto become?
Hepatic veins then inferior vena cava
Explain the surroundings of central veins of lobules?
Hepatic cords radiate out of central veins
Cords composed of hepatocytes
Bile canaliculus lies between cells and within each cord
Spaces between hepatic cords are called hepatic sinusoids
What are hepatic cords that radiate from central vein composed of?
Hepatocytes
What are spaces between hepatic cords called?
Hepatic sinusoids
What are hepatic sinusoids?
Blood channels
What is the direction of blood and bile from the central vein of lobules?
Blood travels towards the central vein
Bile travels away from the central vein
What kind of blood is made once the hepatic artery and hepatic portal vein mix together?
Blood high with oxygen and nutrient content
Why is glucose stored in the liver as glycogen?
Glucose would be a problem osmotically
What is the alimentary role of the liver?
Produce and secrete bile
What does the hepatic artery form before entering hepatic sinusoids then the central veins?
Hepatic portal vein
What would we not be able to do without bile?
Digest fats
What are the 6 components of bile?
Bile acids
Lecithin
Cholesterol
Bile pigments
Toxic metals
Bicarbonate
Which of the 6 components of bile are not synthesised in the liver?
Toxic metals
Bicarbonate
What are bile pigments broken down from?
Haemoglobin from old/damaged erythrocytes
What are the different kinds of bile pigments?
Bilirubin extracted from blood by hepatocytes (yellow)
Bilirubin modified by bacterial enzymes (brown)
Bilirubin reabsorbed from excreted urine (yellow)
What are bile salts synthesised in the liver from?
Cholesterol
How much bile salt is produced per day?
0.5g
How much bile salt do we have in our bodies at one time?
10g
Why is 0.5g of bile salt synthesised everyday?
We lose 0.5g in our faeces and 9.5g is recycled
What happens to bile acids before secretion?
Conjugate with glycine or taurine to form bile salts
Why do bile acids conjugate with glycine or taurin to form bile salts before secretion?
Increases solubility
How are excreted bile salts recycled?
Via enterohepatic circulation:
liver -> bile duct -> gallbladder -> bileduct (returns) -> duodenum -> ileum -> hepatic portal vein -> liver etc
What is the size of the gallbladder?
8cm wide x 4cm long
Where is the gallbladder found?
Inferior surface of liver
What is the function of the gallbladder?
Store and concentrate bile
How does the wall of the gallbladder differ from the general layout of the gut tube?
Only 3 layers, missing submucosa
What are the layers of the gallbladder wall?
Mucosa
Muscularis
Serosa
What is the serosa of the gallbladder formed from?
Connective tissue
What is the purpose of the muscularis layer of the gallbladder?
Smooth muscle for contraction
What is the structure of the mucosa of the gallbladder?
Foled (rugae) for expansion
What is the pathway from the gallbladder to the common bile duct?
Gallbladder -> cystic duct -> common bile duct
What controls the release of bile and pancreatic juice into the duodenum?
Sphincter of Oddi
What happens to bile when the sphincter of Oddi contracts?
Sphincter closes which forces bile back into the gallbladder
To what extent does the gallbladder concentrate bile?
5-20x
Why does the gallbladder absorb Na?
Due to chemical gradient created by Na/K ATPase
Explain the mechanism for the release of bile in relation to fat being present in the duodenum?
1) CCK is released
2) CCK acts on sphincter of Oddi causing it to relax
3) CCK acts on gallbladder causing it to contract
4) Bile is discharged into duodenum causing fat solubilisation
5) CCK acts on pancreatic enzymes increasing bile secretion
Why is it important that CCK controls both bile and pancreatic enzyme secretion at the same time?
Need both bile and lipase to digest fat
Considering the difference in secretin and CCK, what is the function of each?
Secretin is used for neutralisation
CCK is used for digestion
What causes the secretion of secretin?
Acid in the duodenum
What effects does secretin have?
Decreases acid secretion
Decreases acid emptying
Increases HCO3 duodenal secretion
Increases HCO3 pancreatic secretion
Increases HCO3 bile duct secretion
What inhibits the secretion of secretin?
Neutralisation (negative feedback loop)
What causes the secretion of CCK?
Fat/amino acid in the duodenum
What effects does CCK have?
Decreases gastric emptying
Increases pancreatic enzyme secretion
Gallbladder contraction
Relaxation of sphincter of Oddi
Does anything inhibit the secretion of CCK, creating a negative feedback loop?
No
What does CCK stand for?
Cholecystokinin
