Accessory organs of the gut - Liver, Gall Bladder and Pancreas

Question 1

State the accessory organs

Answer 1

liver
gall bladder
pancreas
salivary glands

Question 2

Whats the duodenum?

Answer 2

Accepts the cyme from the contents of the stomach when it empties – link to digestion
- Trypsin and chymotrypsin enzymes secreted in inactive form (prevents autodigestion) in pancreas – activated in alkaline environment of duodenum

Question 3

What are the functions of liver?

Answer 3

• detoxification of metabolic waste
• destruction of spent red blood cells
• secretion of bile (gall bladder secretes and stores)
• synthesis of plasma proteins
• processing and storage of nutrients absorbed from gut tube
• storage of fat-soluble vitamins – eg. Vitamin A + B12 stored here (2 and 3 years of supply)
• storage of glucose (glycogen) – for glycogenolysis

Question 4

What is the falciform ligament?

Answer 4

Ligament that Suspends the liver – also helped by diaphragm

Question 5

What is the liver lobule?

Answer 5

Structural unit of liver
- group of hepatocytes
- hexagonal
- separated by connective tissue with portal tracts
- portal triads at corners of lobules
- a collecting vein for the filtered blood in centre of portal triads

Question 6

What does the portal triad contain?

Answer 6

• artery (nutrient and oxygen rich to the liver cells)
• bile duct – collect bile after secretion
• lymph – collect lymph
• portal vein (bring nutrient rich blood to be filtered)
• vagus nerve

Question 7

What is the structure of the liver lobule?

Answer 7

1. sinusoid – connecting up to relevant hepatic portal vein – these are highly fenetrated or leaky allowing plasma to leak out into surrounding (interstitial space) hepatocytes – for efficient 2 way exchange between blood and hepatocytes
2. central vein – collecting vein blood back to circulatory system – from sinusoid – sent to duodenum but a portion is diverted to gall bladder
3. hepatic portal vein – nutrient rich from gut
4. hepatic artery – bring oxygenated blood
5. bile duct – collect bile salts produced by hepatocytes

Question 8

What does the sinosoid do?

Answer 8

• connecting up to relevant hepatic portal vein
• plasma to leak out into surrounding (interstitial space) hepatocytes
• for efficient 2 way exchange between blood and hepatocytes
• liver

Question 9

Whats the central vein?

Answer 9

collecting vein blood back to circulatory system – from sinusoid – sent to duodenum but a portion is diverted to gall bladder
liver

Question 10

Whats the hepatic portal vein?

Answer 10

nutrient rich from gut
liver

Question 11

Whats the hepatic artery?

Answer 11

bring oxygenated blood
liver

Question 12

Whats the bile duct?

Answer 12

– collect bile salts produced by hepatocytes
liver

Question 13

Whats the space of disse?

Answer 13

• between hepatocytes (secrete bile salts) and hepatic sinusoid (blood rich space)
• Endothelial cells lining sinusoid have gaps allowing blood plasma to permeable into space of Disse
• Space that fills with haemolymph
• Helped by quiescent stellate cells

Question 14

What are hepatocytes?

Answer 14

• Brush border to increase surface area for
• waste metabolites, nutrients
• production of glycogen of glucose storage
• convert amino acids to albumin (blood protein) – ammonia (toxic) into urine

Question 15

What are stellate cells?

Answer 15

• sit in space of Disse
• in quiescent state taking up fatty substances and store vitamins eg. A
• when damaged (excess alcohol) – transform into fibroblasts and lay down fibres – start of liver fibrosis

Question 16

What are kupffer cells?

Answer 16

• must have access to blood
• act as macrophages
• phagocytose RBC and bacteria extracting iron from haemoglobin to recycle haemoglobin structure
• produce bilirubin a component of bile (gives colour of faeces)

Question 17

What does the gall bladder do?

Answer 17

• absorption of water from bile (concentrated now)
• muscular sac
• stores and concentrated bile 5-10x
• tall columnar epithelium with brush boarder (increased absorption of water from bile as surface area)
• Rich supply of Lymph/blood vessels in submucosa to transport water away

Question 18

What does bile do?

Answer 18

• Emulsification of fats (lipids) – into the blood stream
• If bile duct is broken – white streaks in faeces

Question 19

What are the contents of bile?

Answer 19

• Mostly water
• Bile salts – emulsify fats
• Bile pigments – chiefly bilirubin (haem waste product) – broken down into stercobilin
• Cholesterol
• Triglycerides
• Phospholipids – lecithin
• Electrolytes

Question 20

What is bilirubin?

Answer 20

• Bile pigment
• Produced by Kupffer cells
• Broken down into stercobilin – gives faeces its colour

Question 21

What does the pancreas do?

Answer 21

• Exocrine component (80%) - export alkaline fluid, Trypsin and chymotrypsin) - prevents auto digestion
• Endocrine system - insulin and glycogen
• Neutralises acid chyme from stomach
• Other enzymes like lipase and amylase also in pancreatic juice as well as nucleases (to break down DNA and RNA)

Question 22

What assists the control of bile and pancreatic secretion?

Answer 22

• Presence of acidic chyme in intestine stimulates production of intestinal juices (amino acids have same effect)
• Secretin stimulates liver cells to release bile and pancreatic secretion
• CCK stimulates gall bladder to contract and pancreatic secretion