Lecture 11 - Liver Structure and Function

Question 1

What is the largest organ in the body?

Answer 1

The liver at about 1.4Kg

Question 2

Where is the liver located?

Answer 2

In the upper right quadrant of abdomen (tucked against inferior surface of diaphragm)

Question 3

What are the lobes of the liver?

Answer 3

2 major lobes - right (largest) and left

2 minor lobes - caudate and quadrate lobes

Question 4

What ligaments are present in the liver?

Answer 4

The falciform ligament separates the right and left lobes and attaches the liver to the anterior abdominal wall (remnant of ventral mesentery)

The round ligament of the liver (ligamentum teres) originates from the free edge of the falciform ligament (remnant of foetal umbilical vein)

The coronary ligament attaches the bare area of the liver to the inferior surface of the liver

Question 5

What can be found in the centre of the liver?

Answer 5

The porta hepatis - an area where the portal triad can be found, i.e. the hepatic artery, portal vein and common hepatic duct enter and leave the liver

Question 6

What other structures enter and leave the liver via the porta hepatis?

Answer 6

Blood vessels, lymphatic vessels, the hepatic nerve plexus

Question 7

Describe where bile travels after it is produced in the liver

Answer 7

It travels from the hepatocytes (where its make) in the bile canaliculi into the right and left hepatic ducts which feed into the common hepatic duct

The common hepatic duct joins with the cystic duct of the gallbladder to form the common bile duct

The common bile duct then merges with the pancreatic duct, and enters through the major duodenal papilla into the duodenal lumen (release of bile into duodenum controlled by the sphincter of Oddi

Question 8

What happens to the bile if the smooth muscle around the Sphincter of Oddi contracts?

Answer 8

Causes the sphincter of Oddi to close, bile backs up the common bile duct and enters the cystic duct to travel to the gallbladder
Bile is stored and concentrated in the gallbladder

Question 9

What covers the liver?

Answer 9

Liver is covered by a connective tissue capsule (holds liver together) and visceral peritoneum (expect for bare area, which is surrounded by coronary ligament)

Question 10

What surrounds the porta hepatis?

Answer 10

Connective tissue capsule

Question 11

Describe what the liver looks like histologically

Answer 11

Branching network of septa into body of the liver, branching partitions (septa) give the liver structure and support 
Vessels, ducts and nerves follow septa throughout liver 
The septa divide the liver into hexagonal lobules (each corner of each hexagon has a portal triad) - central vein in the middle of each lobule
Hepatic cords (composed of hepatocytes) radiate out from the central veins
Bile canaliculus (cleft-like lumen) lie between cells within each cord - bile etc. secreted into here

Question 12

What are the spaces in between the hepatic chords known as?

Answer 12

Hepatic sinusoids (blood channels) - discontinuous capillaries which allow movement of blood cells

Question 13

What happens to the central veins of each hexagonal lobule?

Answer 13

They come together to form hepatic veins and eventually drain into the IVC

Question 14

What are the brown cells that can be seen in the liver histology?

Answer 14

Hepatocytes which radiate out from the central vein

Question 15

What are bile canaliculi?

Answer 15

Open channels that run from the middle of the hexagon that allow flow of secretions into the bile canaliculi which then come together to form the right and left hepatic ducts

Question 16

Does the blood from the hepatic portal vein or the hepatic artery run towards the central vein or away from it?

Answer 16

Blood from the hepatic portal vein and the hepatic artery run towards the central vein

Question 17

Why is it important that the sinusoids are discontinuous?

Answer 17

Blood coming from the gut is high in nutrients and we want to absorb these and filter any toxins etc.
Blood coming from the artery is high in oxygen, and the hepatic cells are aerobic and obviously need this

Question 18

What is are the functions of hepatocytes?

Answer 18

Bile secretion - PRIMARY ROLE
Nutrient storage (glycogen, fat, vit (B12, A, D, E, K), Cu, Fe)
Nutrient interconversion
Detoxification

Question 19

What are the six components of bile?

Answer 19

Bile acids
Lecithin (emulsification agent)
Cholesterol
Bile pigments (bilirubin)
Toxic metals are detoxified in the liver
Bicarbonate (neutralisation of acid chyme) - stimulated by secretin 

Bile acids, lecithin and cholesterol are synthesised in the liver by hepatocytes and solublise fat
Bile acids, lecithin, cholesterol, bile pigments and toxic metals are secreted by hepatocytes
Bicarbonate is secreted by duct cells

Question 20

What forms bile pigments? What is the predominant bile pigment and where is it excreted?

Answer 20

Breakdown of Hb from old/damaged RBCs
Bilirubin (predominant bile pigment) - extracted from blood by hepatocytes s it passes through hepatic sinusoids and secreted in bile (produces yellow bile)

Question 21

How does bilirubin affect the colour of our faeces and urine?

Answer 21

Bilirubin modified by bacterial enzymes to produce brown pigments (= brown stools_

Reabsorbed bilirubin excreted in urine (=yellow urine)

Question 22

How much bile do we make a day? And how do we maintain a general bile salt pool?

Answer 22

General bile salt pool of about 5g - very efficiently recycled, only loose about 5g a day