Module 5 Section 2 - Excretion

Question 1

What is excretion?

Answer 1

The removal of the waste products of metabolism from the body - these would be toxic if allowed to build up.

Question 2

examples of excreted substances

Answer 2

carbon dioxide, nitrogenous waste (e.g. urea & ammonia)

Question 3

Give two functions of the liver

Answer 3

• The breakdown of metabolic waste products and the break down (detoxification) of other harmful substances e.g. drugs and alcohol.
• Glycogenesis
• • bile production

The liver converts them into less harmful products that can be excreted.

Question 4

How many blood vessels supply blood to the liver? Where from?
What is so special about this?

Answer 4

Two - oxygenated blood from the heart and blood from the small intestine
This is unusual - other organs only have one source of blood.

Question 5

What blood vessel supplies the liver with oxygenated blood?

Answer 5

The hepatic artery.

Question 6

hepatic artery

Answer 6

A blood vessel that supplies the liver with oxygenated blood from the heart.

Question 7

What is the role of the hepatic vein?

Answer 7

To take deoxygenated blood away from the liver.

Question 8

What does the hepatic portal vein do?

Answer 8

Brings blood to the liver from the duodenum and ileum (first and third part of the small intestine respectively) so has lots of the products of digestion.

Hepatic portal vein - products of digestion

Question 9

Compare the sizes of the hepatic artery and hepatic vein.

Answer 9

The hepatic artery is much narrower than the hepatic vein.

Question 10

Why is the hepatic portal vein placed well within the path that nutrients take through the body?

Answer 10

The blood has just come from the small intestine, so means ingested harmful substances are filtered out and broken down quickly before they can cause harm.

Question 11

What is the function of the bile duct?

Answer 11

To take bile produced in the liver to the gall bladder (for storage).

Question 12

What are liver lobules?

Answer 12

Cylindrical structures made of hepatocytes (cells) arranged in rows radiating out from the center.

Question 13

What is found in the centre of a liver lobule?

Answer 13

Central vein that connects to the hepatic vein.

Question 14

Other than in the centre, what else is found in a liver lobule?

Answer 14

• Branches of the hepatic artery
• Brances of the hepatic portal vein
• Branches of the bile duct

Question 15

What connects the hepatic artery and hepatic portal vein to the central vein of a liver lobule?

Answer 15

Capillaries called sinusoids i.e. these sinusoids are where blood flows past hepatocytes in order for harmful substances & oxygen to be absorbed.

Question 16

What three things do hepatocytes do?

Answer 16

• Remove harmful substances and oxygen from the blood
• Break the harmful substances down into less harmful ones (which then re-enter the blood)
• Produce bile and secrete it into bile canaliculi

Question 17

How is the hepatic vein different to the central vein in the lobules?

Answer 17

The hepatic vein is what is formed when the central veins join up.

Question 18

canaliculus

Answer 18

A small passageway e.g. the bile canaliculi

Question 19

What are Kupffer cells, and what are they responsible for?

Answer 19

Resident liver macrophages (perform phagocytosis, do not travel in the blood) attached to sinusoid walls
They remove bacteria and break down old red blood cells.

Question 20

What is the main pigment in bile?

Answer 20

Bilirubin.

Question 21

bilirubin

Answer 21

The substance produced when erythrocytes are broken down.

Question 22

How are bile ducts and bile canaliculi connected?

Answer 22

Bile canaliculi join up and drain into bile ducts. All the bile ducts eventually join up (and then leave the liver).

Question 23

What do all the bile ducts from the lobules eventually do?

Answer 23

They connect up and leave the liver.