Functions of the Liver Flashcards
1
Q
What blood vessels supply the liver and which blood vessels leave the liver?
A
- Hepatic artery supplies oxygenated blood from the heart
- Blood leaves through hepatic vein (deoxygenated blood)
2
Q
Which organs donate deoxygenated blood to the liver and through which vessel? What substances does the dexygenated blood carry?
A
- Spleen, stomach, pancreas, gall bladder, intestines through hepatic portal vein
- Blood contains amino acids, glucose, vitamins, minerals
- The hepatic portal vein allows storage and control of some nutrient levels and allows the detoxification of harmful substances
3
Q
What is a mixture out of oxygenated and deoxygenated blood called?
A
- Dual blood supply (oxygenated from hepatic artery and deoxygenated from hepatic portal vein)
- Liver never receives fully oxygenated blood since the blood mixes when it enters the liver
4
Q
What are the general functions of the liver?
A
- Detoxification of the liver, breakdown and recycling red blood cells
- Regulates nutrient levels
- Conversion of excess cholesterol into bile salts
- Stores iron, vitamin A and vitamin D
5
Q
Explain the structure of the liver.
A
- Triangular shaped organ, consists of 4 lobes
- Each lobe contains 100,000 lobules
- The lobules consist of a central venule from the hepatic vein and 6 venules from the hepatic portal vein and 6 aterioles from the hepatic artery
- The blood vessels are composed of sinusoids
6
Q
What are sinusoids and what are their structure?
A
- Tubes that resemble capillaries but have a discontinuous endothelium
- Incomplete basement membrane
- Fenestrations
- Intercellular gap
7
Q
Compare the structure of capillaries and sinusoids.
A
- Capillaries: very small pores, continuous basement membrane, cylindrical shape, smaller, little intracellular spaces, only small molecule pass
- Sinusoids: fenestrated (pores), discontinuous basement membrane, no definite shape, larger, large intracellular space, leaky
8
Q
What are hepatocytes?
A
- Make up lobules that store substances and are involved in metabolism
- Store iron, Vitamin D and A
- Converts excess cholesterol into bile salts
- Make up 80% of all liver cells
- Can regenerate when exposed to toxic substances
- Rich in mitochondria, Golgi complexes, RER, ribosomes, glycogen granules, lipid droplets
- Detoxification reactions occur in smooth ER
9
Q
How can the liver regenerate?
A
- Regeneration means hepatocytes are replicated, followed by replication of other liver cells
- The newly divided cells undergo restructuring and form the extracellular matrix
- During regeneration, liver function is only partially affected, partial liver donations exist
10
Q
What are plasma proteins? What are the 3 types?
A
- Synthesised by the endoplasmic reticulum and Golgi apparatus in hepatocytes
- They are present in the blood plasma
- Albumins regulate osmotic pressure in blood
- Globulins participate in immune system (antibodies), act as transport proteins
- Fibrinogens involved in clotting process
11
Q
How are red blood cells broken down?
A
- With Kupffer cells, type of white blood cells (macrophages)
- Erythrocytes die after 120 days
1. The macrophages in the liver are Kupffer cells that engulf the RBC by phagocytosis forming a vacuole
2. The vacuole fuses with a lysosome
3. The lysosome breaks down the haemoglobin into globin chains (reused in protein synthesis) & the heme group is separated into iron and bilirubin
4. Iron is carried to the bone marrow to produce more RBC and bilirubin is combined with bile salts to become bile in the small intestine (emulsify fats)
12
Q
What is the role of cholesterol in the liver?
A
- Most cholesterol molecules synthesised in the liver
- Cholesterol is then either stored in membranes of hepatocytes (in the liver) or exported to other cells as lipoproteins or bile salts
- LDL (low density lipoprotein) transports cholesterol from liver to other organs, used in cell membrane and steroid synthesis, LDL raises blood cholesterol levels ‘bad’, has more lipids
- HDL (high density lipoprotein) transports excess cholesterol from tissues back to liver for storage, HDL lowers cholesterol levels ‘good’, has more protein
- Surplus cholesterol converted by the liver into bile salts, eliminated from body through bowels
13
Q
What is the difference between atherosclerosis and arteriosclerosis?
A
- Atherosclerosis is the narrowing of arteries due to plaque, when LDL deposits in the blood vessels and becomes oxidised
- Arteriosclerosis is the hardening of arteries
14
Q
What can HDL do?
A
- It is good cholesterol and removes LDL from the body by transporting it to the liver
- In the liver cholesterol is stored
- It also maintains the endothelium of the blood vessels
- Transports cholesterol from tissues to the liver
15
Q
What are bile salts?
A
- They emulsify fats, break down fats into smaller droplets to increase the surface area
- Allows enzymes to work better
- Bile salts synthesised by liver from surplus cholesterol and are reabsorbed from the intestines into the liver
- Most are lost in faeces, aid in digestion of dietary lipids and fat-soluble vitamins
- Liver produces 1 litre of bile per day, carried to bile duct into gall bladder where it is stored
- Bile composed of water 97%, bile salts, cholesterol and fatty acids, bilirubin
