Excretion, Homeostasis and the Liver

Question 1

Define excretion

Answer 1

the removal of toxic substances, waste products of metabolism and excess substances from organisms

Question 2

Define egestion

Answer 2

the passing of our undigested food as faeces through the anus

Question 3

What is the largest internal organ?

Answer 3

the liver

Question 4

What are the sections of the liver called?

Answer 4

lobes

Question 5

What are liver cells called?

Answer 5

hepatocytes

Question 6

Outline the functions of the mammalian liver

Answer 6

• site of gluconeogenesis, glycolysis, glycogenesis
• stores glycogen
• deaminates excess amino acids, forming ammonia and organic acids. Acids can be respired or converted into glycogen. Ammonia is detoxified by addition of CO2 in ornithine cycle
• detoxifies chemicals e.g. converts alcohol to ethanal then acetic acid

Question 7

Name two substances that need to be excreted from the body

Answer 7

nitrogenous waste (urea) and carbon dioxide

Question 8

What is nitrogenous waste (urea) produced by?

Answer 8

deamination of amino acids in liver

Question 9

What organ is nitrogenous waste (urea) removed by?

Answer 9

kidneys

Question 10

Why does nitrogenous waste (urea) need to be excreted?

Answer 10

urea is toxic

Question 11

What is carbon dioxide produced by in the human body?

Answer 11

cells as a waste product of aerobic respiration

Question 12

What organ is carbon dioxide removed by in the human body?

Answer 12

the lungs

Question 13

Why does carbon dioxide need to be excreted?

Answer 13

excess carbon dioxide in the blood is toxic and can reduce oxygen transport and reduce blood pH

Question 14

The liver receives blood by what two blood vessels?

Answer 14

the hepatic artery and the hepatic portal vein

Question 15

What does the hepatic artery carry to the liver?

Answer 15

carries oxygenated blood

Question 16

What does the hepatic portal veil carry to the liver?

Answer 16

deoxygenated blood rich in products of digestion from the intestines

Question 17

Blood leaves the liver via what blood vessel?

Answer 17

hepatic vein

Question 18

What structure (other than blood vessel) also leaves the liver?

Answer 18

the bile duct

Question 19

What does the bile duct carry from where to where?

Answer 19

carries bile from the gall bladder to the duodenum where it emulsifies fats

Question 20

What are the three stages of urine production?

Answer 20

ultrafiltration, selective reabsorption and water reabsorption

Question 21

Where does ultrafiltration take place?

Answer 21

glomerulus and Bowman’s capsule

Question 22

Where does selective reabsorption take place?

Answer 22

proximal convoluted tubule

Question 23

Where does water reabsorption take place?

Answer 23

loop of Henle, distal convoluted tubule and collecting ducts

Question 24

Give a brief outline of ultrafiltration

Answer 24

• fluid is forced out of capillary blood under hydrostatic pressure into the Bowman’s capsule
• glucose, amino acids, urea and inorganic ions move with it
• large proteins and red blood cells cannot cross into Bowman’s capsule and remain in the blood

Question 25

Give a brief outline of selective reabsorption

Answer 25

Substances reabsorbed into blood:
- 100% glucose
- 100% amino acids
- water
- some inorganic ions

Question 26

Give a brief outline of water reabsorption

Answer 26

• water reabsorbed due to very negative water potential in the medulla tissue fluid
• ADH changes permeability of cell membranes so more/less water is reabsorbed

Question 27

What does ADH stand for?

Answer 27

antidiuretic hormone

Question 28

List the structures of a nephron in order, starting with the glomerulus

Answer 28

glomerulus, Bowman’s capsule, proximal convoluted tubule, loop of Henle, distal convoluted tubule, collecting duct