Excretion (liver)

Question 1

What is excretion?

Answer 1

The removal of metabolic waste products from the body.

Question 2

What are examples of excretory products?

Answer 2

Carbon dioxide, urea, water, and bile pigments.

Question 3

Which organs are involved in excretion?

Answer 3

Lungs, kidneys, liver, and skin.

Question 4

How do the lungs contribute to excretion?

Answer 4

They excrete carbon dioxide, a waste product of respiration.

Question 5

What is the main nitrogenous waste product in humans?

Answer 5

Urea, produced from the breakdown of amino acids.

Question 6

Where is urea produced?

Answer 6

In the liver through deamination and the ornithine cycle.

Question 7

What is deamination?

Answer 7

The removal of the amine group from amino acids to form ammonia.

Question 8

What is the ornithine cycle?

Answer 8

A cycle in the liver that converts toxic ammonia into urea.

Question 9

How is urea transported from the liver to the kidneys?

Answer 9

In the bloodstream, dissolved in plasma.

Question 10

What is the role of the liver in excretion?

Answer 10

It detoxifies harmful substances and breaks down excess amino acids.

Question 11

What is detoxification?

Answer 11

The conversion of toxic substances into less harmful forms in the liver.

Question 12

What enzymes are involved in liver detoxification?

Answer 12

Cytochrome P450 enzymes.

Question 13

What happens to alcohol in the liver?

Answer 13

It is broken down by alcohol dehydrogenase into ethanal, then converted to ethanoate.

Question 14

What is the role of the kidneys in excretion?

Answer 14

They filter blood, remove urea, and regulate water and salt balance.

Question 15

What is the hepatic portal vein?

Answer 15

A vein that brings blood containing digested nutrients from the gut to the liver.

Question 16

What is bile and how is it excreted?

Answer 16

A digestive fluid produced by the liver; bile pigments are excreted in faeces.

Question 17

How does the skin function in excretion?

Answer 17

Sweat glands excrete water, salts, and small amounts of urea.

Question 18

What is jaundice and what causes it?

Answer 18

Yellowing of the skin due to accumulation of bilirubin, often from liver malfunction.

Question 19

What is the hepatic vein?

Answer 19

The vein that carries blood away from the liver to the heart.

Question 20

What is Kupffer cell?

Answer 20

Specialised macrophages in the liver that break down old red blood cells.

Question 21

What pigment is produced when haemoglobin is broken down?

Answer 21

Bilirubin, which is excreted in bile.

Question 22

What is the renal artery and renal vein?

Answer 22

Renal artery supplies blood to the kidneys; renal vein carries filtered blood away.

Question 23

What happens to excess amino acids in the body?

Answer 23

They are deaminated in the liver and converted into urea.

Question 24

Why must ammonia be converted to urea?

Answer 24

Ammonia is highly toxic; urea is less toxic and more easily excreted.

Question 25

What is the structure of the liver?

Answer 25

Made up of lobules, which are cylindrical structures containing hepatocytes arranged around a central vein.

Question 26

What is a lobule in the liver?

Answer 26

A hexagonal unit of liver tissue made of hepatocytes radiating from a central vein.

Question 27

What are hepatocytes?

Answer 27

Liver cells involved in metabolic processes including detoxification, protein synthesis, and bile production.

Question 28

What are sinusoids?

Answer 28

Capillary-like vessels in the liver where blood from the hepatic artery and portal vein mix and flow past hepatocytes.

Question 29

What are canaliculi?

Answer 29

Tiny channels between hepatocytes that collect bile and transport it to bile ducts.

Question 30

What is the function of Kupffer cells?

Answer 30

Macrophages in the sinusoids that break down old red blood cells and pathogens.

Question 31

What is the route of blood flow through the liver?

Answer 31

Hepatic artery and portal vein → sinusoids → central vein → hepatic vein → vena cava.

Question 32

What is the function of the hepatic artery?

Answer 32

Supplies oxygenated blood to the liver.

Question 33

What is the function of the hepatic portal vein?

Answer 33

Carries nutrient-rich blood from the digestive system to the liver.

Question 34

What is the function of the hepatic vein?

Answer 34

Drains blood from the liver and returns it to the vena cava.

Question 35

Why is the structure of the liver important for excretion?

Answer 35

It allows efficient processing and detoxification of blood before returning it to circulation.