Excretion

Question 1

What is excretion?

Answer 1

The removal of metabolic waste

Question 2

What is egestion?

Answer 2

The elimination of faeces

Question 3

Which substances need to be excreted?

Answer 3

CO2
Nitrogen containing compounds (urea)
Other compounds such as bile pigments

Question 4

What are the main excretory organs?

Answer 4

Lungs - removal of CO2 & water vapour
Kidneys - removal of urea
Liver - production of bilirubin and urea

Skin - removal of salts, urea, water etc. via sweat

Question 5

How does oxygenated blood travel to the liver?

Answer 5

Oxygenated blood from the heart travels to the liver via the aorta and hepatic artery

Question 6

What does “hepatic” refer to?

Answer 6

The liver

Question 7

How is blood removed from the liver?

Answer 7

Blood leaves the liver and returns to the heart via the hepatic vein which re-joins the vena cava

Question 8

What is the role of the hepatic portal vein?

Answer 8

It carries the products of digestion to the liver, directly from the intestines

Question 9

Where is bile produced and secreted?

Answer 9

It is produced and secreted in the liver

Question 10

What does “renal” refer to?

Answer 10

The kidneys

Question 11

Where is bile stored?

Answer 11

Bile is stored in the gall bladder

Question 12

Where is bile released?

Answer 12

Bile is released by the bile duct into the small intestine where it then emulsifies fats

Question 13

What are hepatocytes?

Answer 13

Liver cells

Question 14

Features of hepatocytes

Answer 14

Large nuclei
Prominent Golgi apparatus
Lots of mitochondria

Question 15

What are sinusoids?

Answer 15

The space surrounded by hepatocytes

Question 16

Functions of the liver

Answer 16

Control blood glucose levels
Synthesis of bile, cholesterol
Breakdown of hormones
Destruction of red blood cells

Question 17

What is the role of catalase?

Answer 17

Catalase converts hydrogen peroxide to oxygen and water

Question 18

What is the role of Cytochrome p450?

Answer 18

Cytochrome p450 is a group of enzymes used to breakdown drugs

Question 19

What is the role of alcohol dehydrogenase?

Answer 19

Alcohol dehydrogenase breaks down ethanol into ethanal.

Ethanal is then converted to ethanoate

Question 20

Examples of substances broken down by the liver

Answer 20

Alcohol
Paracetamol
Insulin

Question 21

What is transamination?

Answer 21

The conversion of one amino acid to another. This is important as the diet may not always contain the required amino acids

Question 22

What are some adaptations of hepatocytes?

Answer 22

Thin/flat cells allow for short diffusion distance

Fenestrated (tiny openings/pores) increases permeability

Question 23

What is deamination?

Answer 23

Excess amino acids are harmful and can’t be stored as they are nitrogenous.
The hepatocytes remove the amino groups. This forms ammonia which is then converted to urea. Urea is then removed from the blood by the kidneys and excreted via urine

Question 24

What are the functions of the kidneys?

Answer 24

Osmoregulation
Excretion

Filter urea and waste products out of the blood and excrete them

Question 25

What is the role of the renal artery and where is it found?

Answer 25

The renal artery carries unfiltered blood into the kidney. The renal artery branches off the abdominal aorta and are at arterial pressure

Question 26

What is the role of the renal vein?

Answer 26

The renal vein drains blood once it has circulated through the kidneys and inferior vena cava

Question 27

Describe the process of the ornithine cycle?

Answer 27

Ammonia and carbon dioxide combine with ornithine to produce citrulline and water. Citrulline is converted to arginine (removal of water). Arginine is then re-converted to ornithine by the addition of water and removal of urea.

Question 28

Where is the site of ultrafiltration in the nephron?

Answer 28

The glomerulus

Question 29

What is filtered out of the blood and into the bowman’s capsule?

Answer 29

Water Amino acids Glucose Urea Inorganic ions (Na+, Cl-)

Question 30

What is not filtered out of the blood into the nephron and stays in the capillary instead?

Answer 30

Blood cells Large proteins

Question 31

Why does the afferent arteriole have a wider lumen than the efferent arteriole?

Answer 31

The afferent arteriole is wider which maintains a higher hydrostatic pressure. More blood enters the glomerulus and less blood leaves.

Question 32

How does water enter/increase in the body?

Answer 32

Good Drink Metabolism (respiration)

Question 33

How does water leave the body?

Answer 33

Urine Sweat Faeces Water vapour in exhaled air

Question 34

What happens when water potential falls in the blood?

Answer 34

The pituitary gland is stimulated to produce ADH. Thirst is increased

Question 35

Which organ detects changes in water potential in the blood?

Answer 35

The brain (hypothalamus)

Question 36

What organ breaks down ADH when it is no longer needed?

Answer 36

The liver

Question 37

What kind of control (feedback) is osmoregulation?

Answer 37

Negative feedback control involving osmoreceptors in the hypothalamus

Question 38

What are possible causes of kidney failure?

Answer 38

Blood loss following an accident High blood pressure Diabetes Overuse of certain drugs

Question 39

What two substances may be detected in the urine following kidney damage/failure?

Answer 39

Blood Large proteins

Question 40

What are some effects of kidney damage/ failure?

Answer 40

Loss of electrolyte balance Build-up of urea Weakened bones High blood pressure

Question 41

What is the glomerular filtration rate (GFR)?

Answer 41

It is a measure to indicate kidney disease

Question 42

What is the normal GFR?

Answer 42

90-120 cm3 /min

Question 43

What is the GFR for chronic kidney disease?

Answer 43

Below 60cm3 / min

Question 44

What is the GFR for kidney failure?

Answer 44

Below 15cm3 / min

Question 45

What treatment option are available if both kidneys are damaged?

Answer 45

Renal dialysis Kidney transplant

Question 46

What is the name of that hormone that is detected in a pregnant persons urine?

Answer 46

hCG

Question 47

How are monoclonal antibodies produced?

Answer 47

A mouse is injected with hCG so it makes that appropriate antibody in response. The B cell that make the antibody are then removed from the mouse and fused with a myeloma (a type of cancer cell). This is now called a hybridoma. Each hybridoma reproduces rapidly resulting in a clone of million of cells making the desired antibody. The antibodies are collected, purified and used in a variety of ways

Question 48

How are sodium ions reabsorbed into the blood from the nephron?

Answer 48

1) Na+ ions are actively pumped out of the cells lining the tubule. K+ ions are moved into the tubule so the charge is equal 2) Na+ conc. in the cells cytoplasm decreases, creating a conc gradient 3) Na+ diffuse into the cell through a co-transport protein - carrying glucose or an amino acid at the same time 4) water moves into the cell by osmosis as a result 5) Glucose/Amino acids diffuse into the blood. Water follows

Question 49

What is gas chromatography?

Answer 49

Urine same is vaporised and passed through a column containing a polymer. The substances in the urine travel through the column at different speeds so separate out.