15.4 Excretion, Homeostasis And The Liver

Question 1

Excretion

Answer 1

Removal of waste products of metabolism from the body

Question 2

Main metabolic waste products

Answer 2

Carbon dioxide
Bile pigments
Nitrogenous waste products (urea)

Question 3

How is CO2 excreted?

Answer 3

Waste products of cellular respiration excreted from the lungs

Question 4

What are bile pigments?

Answer 4

Breakdown of haemoglobin from old RBCs in the liver

Question 5

How are bile pigments excreted?

Answer 5

Excreted in the bile from the liver into the small intestine via the gall bladder and bile duct

Question 6

Why is urea formed?

Answer 6

From breakdown of amino acids in the liver

Question 7

How is urea excreted?

Answer 7

By the kidneys in the urine

Question 8

Blood vessel that supplies liver with oxygenated blood

Answer 8

Hepatic artery

Question 9

Blood vessel that removes deoxygenated blood from the liver

Answer 9

Hepatic vein

Question 10

Hepatic portal vein

Answer 10

Carries blood containing products from digestion from the intestines to the liver

Question 11

Hepatocytes adaptations

Answer 11

Large nuclei
Prominent Golgi apparatus
Lots of mitochondria
Metabolically active cells

Question 12

What happens in the sinusoids?

Answer 12

Blood from the hepatic artery and hepatic portal vein is mixed
This increases O2 content of blood supplied to hepatocytes

Question 13

Kupffer cells

Answer 13

Act as macrophages for liver
Ingest foreign particles, help protect against disease

Question 14

Journey of bile from liver

Answer 14

Hepatocytes secrete bile from RBC breakdown into canaliculi
Bile drains into bile ducts that take it to the gall bladder

Question 15

Functions of liver

Answer 15

Carbohydrate metabolism
Deamination of excess amino acids
Detoxification

Question 16

Carbohydrate metabolism

Answer 16

When blood glucose concentration rises, insulin rises and hepatocytes are stimulated to convert glucose into glycogen
When blood glucose concentration falls, hepatocytes convert glycogen back into glucose due to glucagon

Question 17

Transamination

Answer 17

Conversion of one amino acid into another

Question 18

Deamination

Answer 18

Removal of amine group from a molecule
Body cannot store amino acids or proteins, so excess would be excreted and wasted without hepatocytes
Deaminate amino acid - convert into ammonia - urea

Question 19

How is ammonia converted into urea?

Answer 19

Via the ornithine cycle

Question 20

How is hydrogen peroxide broken down?

Answer 20

Hepatocytes contain catalase enzyme
Splits hydrogen peroxide into oxygen and water

Question 21

How is alcohol broken down?

Answer 21

Alcohol dehydrogenase
Ethanol is broken down into ethanal
Ethanol broken down into ethanoate - used in respiration, or to build fatty acids

Question 22

Cirrhosis

Answer 22

Normal liver tissue is replaced by fibrous scar tissue

Question 23

Stages of alcoholic liver disease

Answer 23

1- alcoholic fatty liver disease
2- alcoholic hepatitis
3- liver cirrhosis

Question 24

Alcohol fatty liver disease

Answer 24

Big fat filled vesicles displace nuclei of hepatocytes and liver gets larger

Question 25

Alcohol hepatitis

Answer 25

Fatty liver as well as damaged hepatocytes, sinusoids/hepatic veins become narrowed

Question 26

Alcoholic cirrhosis

Answer 26

Liver tissue is irreversibly damaged
Hepatocytes die and replaced with fibrous tissue
Hepatocytes can no longer divide, so liver shrinks and loses ability to deal with toxins in the body