Liver & Pancreas

Question 1

What are the two ducts in the pancreas?

Answer 1

• main pancreatic duct

- common bile duct

Question 2

What enzymes are made in the pancreas?

Answer 2

Majority used in duodenum.

Question 3

What important substance does the pancreas make?

Answer 3

Bile

Question 4

What are the two types of cells in the pancreas?

Answer 4

• Exocrine (salivary glands)

- Endocrine (islets of Langerhans)

Question 5

Pancreas:
What does the exocrine part look like?
What is the structure?
How does it secrete?
Are there any mucus producing cells?
What cell is most abundant here?

Answer 5

• parotid gland
• typical branched acinar structure
• merocrine secretion
• no mucus producing cells here
• enzyme producing cells are more abundant cell here

Question 6

What cells line the lumen of the pancreas?

Explain where the nucleus is

Answer 6

Centroacinar cell

All enzyme producing cells have the nucleus at the bottom of the cell to move the nucleus so efficient secretion can occur. Occasionally you have a nucleus in the middle of the cell which are the centroacinar cells.

Question 7

What is the function of the centroacinar cell?

Answer 7

To produce bicarbonate ions. The secretions pass into the intercalated duct and then into the excretory duct.

Question 8

Explain the two differences between the pancreas and the salivary glands down the microscope

Answer 8

Pancreas:

• No striated ducts
• Centroacinar cells

Salivary Gland:

• Striated ducts abundant
• No centroacinar cells

Question 9

Why do the islets of langerhans have a high blood supply?

Answer 9

These cells trap around the capillary so can efficiently deposit their hormone secretion into the bloody supply.

Balls of cells producing insulin, glucagon, somatostatin, pancreatic polypeptide and vasoactive intestinal peptide.

Question 10

What happens with a pancreatic tumer?

Answer 10

Causes enzymes to enter the body cavity which causes cells to digest the body.
Makes pancreatic surgery hard.

Question 11

Give the 8 functions of the liver:

Answer 11

1) Exocrine = production of bile
2) Processes absorbed nutrients
3) Carbohydrate, fat and protein metabolism
4) Stores - carbohydrates, lipids, vitamins
5) Synthesises - plasma proteins (involved in transport), lipoproteins
6) Detoxification of ingested toxins, drugs
7) Destroys red blood cells and reclaims iron
8) Site of haematopoiesis in embryo

Question 12

Explain the structure and organisation of the liver

Answer 12

Roughly hexagonal but less distinct due to there being less connective tissue between lobules.

Has a central vein in the middle - where the processed blood exits the liver lobule.

Triads - where the blood enters the liver.

Question 13

What are the two sources entering the lobule?

What exits the lobule?

Answer 13

1) The portal vein (brings blood from the small intestine containing the absorbed nutrients)
2) Hepatic artery (brings oxygenated blood)

Bile moving out to the bile duct.

Question 14

How are hepatocytes arranged?

Answer 14

Arranged in rows
- blood flows in-between

Major cell type is in hepatocyte. They sit aside sinusoids. They are cuboidal either occurring in one or two layers.

Question 15

What two cells line the sinusoids?

Answer 15

• Endothelial cells

- Kupffer cells (phagocytic cells)

Question 16

What do hepatocytes have which then extend?

Answer 16

Microvilli which extend into space of Disse.

Question 17

What are the cells called with are formed in the space of Disse?

What can these cells transform into and why?

Answer 17

Stellate cells (has lipid droplets in them which store vitamin A).

Into myofibroblasts in response to inflammatory stimuli. They begin to lead down collagen which can leads to cirrhosis.

Question 18

When can the liver not regenerate?

Answer 18

If cirrhosis has occurred.

Question 19

Why are there gaps in the endothelial cells?

Answer 19

Where the microvilli project to allow the lipid part of the blood to come in direct contact with the hepatocyte to increase efficiency of uptake and to cause proteins from the hepatocyte to enter the blood.

Question 20

What makes hepatocytes specialised?

Answer 20

• highly compact
• surfaces are specialised in different ways
• polarised (has a direction) along all axis

Question 21

What are the things which you can secrete and absorb?

Answer 21

Secretion: albumin, fibrinogen (plasma proteins), clotting factors

Absorption: blood-borne substances (food, drugs)

Question 22

Explain the hepatocyte metabolic activity

Answer 22

Crowded with organelles, reflecting the high biosynthetic and degradative activity.
Lots of smooth endoplasmic reticulum to produce vesicles for secretion.

Question 23

How does bile leave the liver? Explain this

How do we prevent bile from getting between the cells?

Answer 23

Bile canaliculi keeps blood and bile separate. They have microvilli in them.

Tight junctions between cells.

Question 24

What are the two things bile contains?

Answer 24

• bile salts (sodium glycocholate, deoxycholate, taurocholate) synthesised from cholesterol, acts as detergent to emulsify fats in the duodenum
• bile pigments (bilirubin and biliverdin) breakdown products of haemoglobin, lysosomes fuse with them and then broken down, products of Hb breakdown goes into the bile

Question 25

What is an acinus formed from?

Answer 25

Two adjacent triads

Question 26

What are the 3 zones in hepatocytes?

What is metabolised in region 1 and 3?

Answer 26

1: blood most oxygenated, nutrient-rich
2: intermediate
3: blood depleted of oxygen and nutrients

Region 1 metabolises glucose. Region 3 metabolises glycogen.

Question 27

What is toxic to region 1 and region 3?

Answer 27

Region 1 - the toxin

Region 3 - byproducts of the toxin

Question 28

Explain the breakdown of paracetamol?

Answer 28

Paracetamol is metabolised by P450s producing a derivative. Byproduct of metabolism called quinone is what is toxic to the body. This is going to kill region 1 cells (closest to central vein).
The affect of this on region 1 is irreversible.

Question 29

What does cirrhosis do to the lobule body?

Answer 29

Cirrhosis has deposition of extra cellular matrix within lobule body which prevents diffusion of blood from the triad across the lobules.

Question 30

Give as many details on the gall bladder as possible

Answer 30

• Stores and concentrates bile (about 50ml)
  Na+ - K+ ATPase pumps in basal and lateral membranes of epithelium

Walls of the gall bladders in fold.
One cell type present.
Brush border to increase efficiency of pumping ions across it.
Thin layer of smooth muscle around this.
Tall, simple columnar epithelium with an irregular brush border.
Cholcystokinin causes bile to be released by causing the smooth muscle to contact when food arrives.

Question 31

Why is there gaps between the basal surfaces of adjacent cells in the gall bladder?

Answer 31

Due to the influx of water following the pumping out of NaCl into the interstitial space.