Sem 2 W2- Liver physiology

Question 1

Liver physiology

Describe the anatomy of the liver

Answer 1

AA~~~~~~~~~~~~~~~~~~~~~~~~~~~~~1. Made up of left and right LOBE

2. Each lobe is divided into 8 LOBULES

• Each lobule is made up of a central vein, radiating sinusoids ( capillaries), bile ducts, hepatocytes etc

3. Capillaries join to make veins
4. Bile ducts join to form common bile duct
5. Bile duct drain bile into duodenum after being stored and concentrated in the gall bladder

Question 2

Describe what products are synthesised in the liver

Answer 2

1. Hormones
   - Insulin-like growth factor
   - Thrombopoietin - stimulates platelets
2. Plasma proteins
   - Coagulation factors
   - Transport for cholestrol (lipoproteins)
   - Transport for steroid and thyroid hormones
   - Angiotensinogen - important in salt conservation

Question 4

Describe the internal vascular system of the liver

Answer 4

The aorta carries blood from oxgen to the right + left hepatic arteries ( via the lobes)

The hepatic vein carried deoxygenated blood from the liver back to the heart via inferior vena cava

The liver also has a portal vein carries nutrient rich deoxygenated blood from the GI tract towards the liver to be filtered before distrivbuted around body

Bile duct gather and form common bile duct forms gall bladder of storing bile

Question 6

Describe the structure and function of the hepatic lobule

Answer 6

Lobules hexaginal strucutured , middle cdntral vein ouut sifde portal triad ( hepatic artery, portal vein and bile duct) - blood arrives form outisde in heptaic arteriy then into sinusoidal cappilaries which join again to central vein gtaking deoxygented blodd away

hepatocytes basic cell structure store everything in the liver

Bile cannaliculi between the heptocytes which gatehrs into the bile ducts taking the bile formed by hepatocytes away

Question 7

Heptaitc lobule st

Answer 7

The central veins in the middle of the hexagonal structure of the hepatic lobule

inside theres central vein on the outside of the structure the portal triad

surrounding the central vein are the hepatocytes, from the portle vein the sinusoids join together to form the central vein

between the hepatocytes are the bile canniculus

other cells afre macrophages and Kupfer cells involved in phagocytosis of foreign substance

other cellls involved are fibrocyte and hepatic stellate cells important in supporting hepatocytes

as liver diseases progresses hepatic stellate cells initiate fibrosis occurs

kupfer cellls become inflammaory cells dyeing inflammation

Question 8

functions of liver

Question 9

Decribe the metabolic processes of nutrients

Answer 9

Carbohydrates
Stores glucose as glycogen
when stored as glycogen it is stored with water so it is not as energy dense as fat but kept for cases in fasting
when fasting gluconeogensis for breakdown

Lipid

synthesis of cholestrol happens here (85%)
cafrried arounf the body in lipoproteins are VLDL, LDL, HDL

Protein
- Amino acid synthesis ( non- essential amino acids)
- breakdown of amino acids to ammonia and urea for exctretion

Question 10

Detoxification and degradation in the liver

Answer 10

• harmful ammonia can be converted to urea
• also a major ways of removing nitrogenous waste

Detoxification of drugs and xenobiotics ( food contaminants)
done by
- Phase 1 reactions - by Cytochrome P450 enzymes
- Phase 2 reaction enzymes are done via conjudgation techniques gluconsiltranferase males it less tocixx and more hydrophillic

these enzymes can be affected by age, diet and genetic influence ( polymorphisms affact how well these metabolic processes occur and the fuction of the enzymes )

Answer 11

• Hormone modifications
• Vitamin D3 converted to 25-OH vit D3 in liver to kidney 125 vitamin D3
• Thyroid hormone conversion from T4 to T3
• Insulin like growth factors produced by hepatocytes, these are used in the modification of growth hormone(s)

Degredation of hormones
- breaks down insulin and glucagon
- Oestrogens, glucocorticoids and growth hormone , PTH
- GI hormones also degraded here including gastrin

Question 12

Storage in the liver

Answer 12

• Fat is stored in the liver ( can cause complications in obesity and first stage liver disease)
• Glycogen
• Trace elements- Copper, Iron

Vitamins: fat soluble
- Vitamin A
- Vitamin D
- Vitamin K

• Water soluble vitamins are retained for a short period of time exxcept b12

Question 13

Describe the products synthesised in the Liver

Answer 13

1. Iron transport and metabolism proteins - to avoid prooxidative damage to vascular cells

• Transferrin - used in iron transport
• heptaglobin - used in free haemoglobin binding
• Hemopexin - used for fre HAEM binding
• Hepcidin - inhibits gut iron uptake

2. Acute phase proteins
   -Important in inflammation
3. Bile acids
   - Primary - cholic acid & chenodeoxycholic acid
   - Secondary - deoxycholic acid & lithocholic acid

Question 14

Describe what bile is and its function ( speicifcally bile salts)

Answer 14

• Alkaline fluid ( made of bile salts, cholestrol, Lecithin & Bilirubin)

Bile Salts
- Derived from cholestrol
- Bile salt + Lecithin convert fat globules into liquid emulsion

• Helps in Micelle formation
• Lipid soluble centre, with bile salts + lecithin has water and lipid soluble portions
• Bile salt + lecithin shell is inbetween hydrophillic and hydrophobic shell

Question 15

Name how cholestrol is excreted

Answer 15

• Cholestrol and billiruben ( a by product from broken down haem ) in excreted when bile is secreted

Question 16

Describe the process of

Answer 16

1. Heme is broken down into biliruben in the macrophages from the tissue and liver ( hemeoxygenase )
2. Unconjugated biliruben is transported to the liver in the blood
3. Biliruben taken up by th eliver via diffusion and then is conjugated with glucuronic acid
4. conjugated biliruben secreted into the bile + intestine
5. Glucuronic acid removed leaving remaining biliruben to be converted to urobilinogen
6. Some urobilinogen is reabsorbed and enters portal blood
7. Then transported to kidney where converted to urobilin
8. Urobilinogen is oxidised by intestinal bacteria to brown stercobilin to feces

Question 17

Describe the immunological function in the liver

Answer 17

• Carried out in the reticuloendothelial system
• Kupfer cells attached to endothelium phagocytose antigens which were carried from the GI tract from the portal vein
• **Hepatic stellate cells **
• Perisinusoidal:
• Antigen-presenting role
• Major cell involved in liver fibrosis
• Other immune cells

-Role in inflammatory response