Excretion

Question 1

Define excretion

Answer 1

The removal of toxic waste substances which have been made by cells

Question 2

Define egestion

Answer 2

Waste (faeces) which has passed through the alimentary canal without entering cells

Question 3

What are the excretory products of the lungs, kidneys and skin

Answer 3

Lungs via blood plasma- CO2, made in respiring cells by respiration
Kidneys & skin - urea, made in liver cells by breakdown of amino acids (dreamination)

Question 4

Describe the origin of o2 and co2 as waste products

Answer 4

CO2 is a waste product of respiration via the lungs in humans and leaves in plants
Plants - loss from stomata and guard cells
Humans - metabolism

Question 5

Describe urea formation

Answer 5

1. Amino acids are filtered into liver along with rest of blood via hepatic artery
2. Excess amino acids cannot be stored and are broken down to carbs and ammonia
3. Ammonia is toxic and must be broken to urea
4. Amino acids that are needed and the urea are released back into the blood stream via the hepatic vein

Question 6

Describe the structure of the excretion system

Answer 6

Blue tube = renal vein, red tube = renal artery
Kidney
Ureter
Bladder
Urethra

Question 7

Describe the structure and function of the kidneys

Answer 7

Filters blood and removes any excess materials and passes them to the bladder to be excreted. They contain 3 sections, the top and a lighter colour is the cortex, middle is the triangle shaped medulla and finally is the centre yellow pelvis, it also has millions of tiny nephrons

Question 8

What is ultra filtration?

Answer 8

where lots of water, ions, urea and sugar are squeezed form the blood into the tubules

Question 9

What is selective reabsorption?

Answer 9

the useful substances (sugar, ions) are reabsorbed into the blood from the tubules, amount of water is regulated here to maintain it at a constant rate (osmoregulation)

Question 10

Describe ultrafiltration

Answer 10

1. size of artery at exit of glamorous is smaller than entrance, which builds pressure
2. forces small molecules (urea, glucose, amino acid, salt) into bowman capsule and from glomerular filtrate
3. larger molecules (protein, red blood cells) are too big so they stay in the blood

Question 11

Describe selective reabsorption

Answer 11

1. filtrate travels to proximus convoluted tubule but useful materials would be wasted
2. specialised cells in pct pump useful materials back into the blood stream against conc gradient using energy (active transport)

Question 12

What is water reabsorption?

Answer 12

loop of henle and collecting duct, if you have lost a lot of water then body will try and absorb as much as possible from the filtrate (darker urine), but if you have excess water it will contain high vol and low conc (paler)

Question 13

Describe water reabsorption

Answer 13

body maintains water levels with anti diuretic hormone by the hypothalamus monitoring the level of water in blood and if it needs to absorb more then it tells the pituitary gland.
as adh is a hormone it travels in the blood, the collecting duct is surrounded by capillaries and the ad diffuses out blood and binds what receptors on the surface collecting duct cells, which triggers the collecting duct to become more permeable to water, more absorbed