The liver

Add stuff about detoxification and cirrhosis and alcohol

What are liver cells called?

What are liver cells called?

Heapatocytes

What connects the liver to the small intestine and supplies it with nutrients?

Portal vein

What supplies the liver with oxygenated blood?

Hepatic artery

What histological structures is the liver made up of?

lobules

How many lobes does the liver have?

2, left and right

Where is the liver located?

Right side of the abdomen, below the diaphragm

What transports deoxygenated blood away from the liver?

Hepatic vein

What main nutrients can the liver store?

• glycogen

• iron

• vitamin A

• vitamin D

What are the 4 main functions of the liver?

1. controlled storage and release of key nutrients

2. detoxification of harmful ingested substances

3. breakdown of blood cells and production of bile salts

4. production of plasma proteins

Describe the following picture and what is happening.

• hepatic artery provides oxygen

• portal vein provides nutrients

• hepatocytes produce bile which drains into the bile ducts

• sinusoids allow for the exchange of materials within the hepatocytes

What vessels transport bile t bile ducts?

Caniculi

What are sinusoids?

Capillaries (blood vessels) with increased permeability (incomplete basement membrane and intercellular gaps)

Why is permeability of sinusoids important?

It allows for larger molecules to pass through

What are the two layers of a capillary and how are they different in sinusoids?

• Endothelial layer (inside)

• Basement membrane (outside)

• In sinusoids there are intercellular gaps in the endothelial layer and the basement membrane is incomplete

What does the liver do with nutrients received from the portal vein?

1. It converts the nutrients into forms that can be stored or used

2. Mediates transport of nutrients in various tissues

What 3 biological molecules does the liver metabolise?

1. Carbohydrates

2. Protein/amino acids

3. Lipids

How does the liver regulate blood sugar?

It takes up excess glucose in the bloodstream and stores it as glycogen

What does the liver do if blood sugar levels start to drop?

breaks down glycogen into glucose and exports it to body tissues

What happens when hepatic glycogen reserves become exhausted?

the liver synthesises glucose from other sources (eg fats)

What pancreatic hormones aid the liver in regulating blood sugar?

Insulin (high blood sugar)

Glucagon (low blood sugar)

How many essential amino acids are there?

9

What is the difference between an essential amino acid and a “regular” amino acid?

The body can only get non-essential amino acids through the diet whereas “non-essential” amino acids can be synthesised through transamination (if essential amino acids are in excess).

Why is it important that the liver metabolises amino acids?

They can not be stored by the body and must be broken down. The nitrogen of the amine group (NH2) can be toxic.

What are the steps of amino acid metabolism?

1. Transamination

2. Deamination

3. Urea synthesis

What happens in transamination?

Amino acid 1 + Keto acid 2 <→ Amino acid 2 + Keto acid 1

What happens in deamination?

The amine group is removed from the amino acid which forms ammonia and a keto acid

What two things are necessary for the occurrence of deamination?

Electron/Hydrogen carriers (NAD)

Enzymes (eg glutamate dehydrogenase)

What happens in urea synthesis?

ammonia is converted to urea (through the urea cycle) which can then be excreted by the kidneys

What molecule is needed to convert ammonia to urea?

ATP (3 per molecule)

What does the liver do to excess carbohydrates and proteins?

converts them to into fatty acids and triglycerides

What important molecules does the liver synthesise (other than amino acids)?

cholesterol

phospholipids

What do LDL and HDL stand for?

Low density lipoprotein

High density lipoprotein

What is the role of LDLs?

Transports/stores cholesterol within the blood stream

Why can the transport/storage of cholesterol in the bloodstream by LDLs be problematic?

Excess can cause plaque or blockages which clogs arteries and harms the circulatory system

What is the role of HDLs?

Regulate LDL storage and promote excretion (prevent blockage of bloodstream)

What happens to surplus cholesterol?

It is converted into bile salts by the liver which can be excreted via the bowels

When will the liver break down amino acids?

When they are in excess

What group of enzymes mediates the conversion of toxins in the liver?

Cytochrome P450

What is a conjugation reaction?

Attaching a group (hydrophilic) to a molecule that was toxic to make the molecule water soluble

Where in hepatocytes are plasma proteins synthesised?

Rough endoplasmic reticulum

Where are plasma proteins found?

In the blood (blood plasma)

What are the three major types of plasma proteins?

Albumin, Globulins, Fibrinogens

What is the function of the  plasma protein Albumin?

Maintains osmotic pressure in the blood

What is the role of Fibrinogens in the blood?

Involved in blood clotting

Why do R.B.Cs need replacing?

They die due to not being able to divide (no nucleus)

What is the medical term for red blood cell?

Erythrocyte

What cells in the liver are responsible for breaking R.B.Cs down?

Kupffer cells

What is a Kupffer cell?

Type of phagocyte (white blood cell)

What do Kupffer cells break haemoglobin down into?

Globin and a iron containing haem group

An iron containing heme group is broken down into?

Bilirubin and iron

How does bile travel from the gall bladder to the small intestine?

Bile duct

What do the sinusoids connect to?

A central vein which connect to the hepatic vein

What causes Jaundice?

A build up of Bilirubin

What are symptoms of Jaundice?

Yellowing of the skin and whites of the eyes