Liver Structure and Function

Question 1

Two major lobes of the liver?

Answer 1

Left & Right

Question 2

Two minor lobes of the liver?

Answer 2

Caudate - posterior, just anterior to IVC

Quadrate - Anterior, between gallbladder and falciform ligament

Question 3

Where do the neurovasculature, ducts and lymph vessels enter/exit the liver?

Answer 3

Through the porta hepatis on its inferior side

Question 4

What blood vessels enter the porta hepatis? Nerves?

Answer 4

Hepatic portal vein and hepatic artery

Hepatic nerve plexus

Question 5

What duct leaves the liver at the porta hepatis? Where does it go?

Answer 5

The common hepatic duct (R + L hepatic ducts)
Moves inferiorly until anastomoses with cystic duct to form the common bile duct, which also receives secretion from the pancreatic duct before the sphincter of oddi

Question 6

Is the liver fully peritonised?

Answer 6

Yeah its intraperitoneal

There is the “bare area” on the diaphragmatic surface, which is attached to the diaphragm by the coronary ligament - but the ligament is just a reflection of peritoneum

Question 7

How is the liver divided into hexagonal lobules?

Answer 7

CT enters the liver at the porta hepatis, branches out within the liver separating it into lobules
Branches called septa

Question 8

How is blood from the lobules drained?

Answer 8

Central veins are at the centre of each lobule, drain to hepatic veins - IVC

Question 9

What is located at the corners of each hexagonal lobule?

Answer 9

Portal triad - hepatic portal vein, hepatic arteries and hepatic duct

(Also lymph vessels and nerves)

Question 10

Describe the flow of blood and within the hexagonal lobules of the liver

Answer 10

Blood moves from the hepatic portal veins and arteries of the portal triad inwards towards the central veins, which lead to the IVC (a. & v. blood combine)
Bile moves from the hepatocytes to the bile canaliculi (lead to hepatic duct)

Question 11

What are hepatic cords?

Answer 11

Lines of hepatocytes raidiating out from the central vein, between bile canaliculi and hepatic sinusoids
They are the functional cells of the liver

Question 12

What are hepatic sinusoids?

Answer 12

Channels between the hepatic cords (blood channels)

Question 13

Functions of hepatocytes?

Answer 13

Bile synthesis
Nutrient storage (glycogen, fats, vitamins, Cu, Fe)
Detoxification (metals, other toxins)
Nutrient interconversion (eg. carbs to fat)
Processing spent RBC’s

Question 14

Main alimentary role of the liver?

Answer 14

Production and secretion of bile

Question 15

Six components of bile?

Answer 15

1. Bile acids
2. Lecithin
3. Cholesterol
4. Bile pigments (bilirubin)
5. Metals (been detoxified by liver)
6. Bicarbonate
   1-5 - hepatocytes, 6 - duct cells

Question 16

One major function of the liver (hepatocytes) that is crucial to bile production?

Answer 16

Solubilization of fats

Question 17

What are bile pigments? How are they excreted?

Answer 17

Breakdown products of haemoglobin - esp. bilirubin
Bilirubin extracted from blood by liver, solubilized, secreted with bile (yellow bile pigment)
Then modified by bacterial enzymes in gut and excreted as faeces (brown pigment)
Any reabsorbed bilirubin excreted in urine (yellow pig.)

Question 18

What are bile acids? How are they secreted?

Answer 18

Bile acids formed from cholesterol in liver, crucial for fat absorption and digestion

Conjugated with glycine/taurine (made soluble) - bile salts
Bile salts secreted, then recycled by enterohepatic circulation

Question 19

How does enterohepatic circulation recycle bile salts?

Answer 19

Bile salts secreted to duodenum where they are active
Reabsorbed in the ileum
Ileum - hepatic portal vein - back to liver - bile

Question 20

Function of gall bladder?

Answer 20

When bile duct is full, take in some bile - dehydrate it (make it more concentrated)
Then store until secretion

Question 21

3 layers of gall bladder wall?

Answer 21

Mucosa (folded rugae - expands)
Muscularis (contraction)
Serosa (CT)

Question 22

Describe control of bile secretion

Answer 22

Sphincter of oddi
-when contracted, bile forced back into gall bladder
- when relaxed bile released into duodenal papilla
CCK causes the sphincter to relax

Question 23

How does the gall bladder concentrate bile?

Answer 23

Absorbs Na through channels, pumps out through basolateral membrane vie Na/K exchanger
Water follows Na into the body, out of bile
K back out of GB epithelium through leaky channels (maintain gradient)