Kidneys + Excretion

Question 1

Proximal convoluted tubule

Answer 1

Close to Bowman’s capsule
- Ion + water reabsorption
- Na+ actively reabsorbing Cl- passively follows
- Water passively reabsorbed (goes where party is)
- Urine composition does not change

Question 2

Convoluted =

Answer 2

Complex / twisted

Question 3

Distal convoluted tubule

Answer 3

Farther away from Bowman’s capsule
- Alters urine composition
- Active NaCl reabsorption (some water follows)
- Extra “free” water that needs to be excreted = U/P <1
- Altered by anti-diuretic hormone = alters water permeability

Question 4

Low ADH in distal convoluted tubule =

Answer 4

Diuresis = dilute urine (U/P<1)
- Poorly permeable to water

Question 5

High ADH in distal convoluted tubule =

Answer 5

Anti-diuresis = concentrated urine (U/P >1)
- Highly permeable to water

Question 6

Describe the mammals convoluted tubules?

Answer 6

Cortex (Proximal convoluted tubule) –> deep in the medulla (Loop of Henle) –> Cortex (Distal convoluted tubule) –> deep in medulla (Collecting duct)

Question 7

Purpose of Loop of Henle?

Answer 7

Sets up NaCl concentration in interstitial fluid

Question 8

Describe the process of the Loop of Henle?

Answer 8

• Descending + ascending limb –> urine flowing in opposite directions
• Ascending limb = NaCl actively transported out, water cannot follow
• Descending limb = permeable to water, water moves out due to NaCl actively transported out the ascending limb

Question 9

Anti-diuresis

Answer 9

Concentrated urine
- Dilute urine coming in distal convoluted tubule –> water moves out –> urine starts to concentrate
- Urine lows down collecting duct it encounters higher and higher NaCl in interstitial fluid –> water moves out –> concentrate urine
- High ADH

Question 10

Diuresis =

Answer 10

Dilute urine
- DCT + collecting duct become poorly permeable to water
- Water remains in nephron = dilute urine

Question 11

Nitrogen excretion - Ammonia

Answer 11

Marine invertebrates, freshwater & marine fishes, tadpoles
- Highly toxic
-Highly soluble
- Cheap - no ATP

Question 12

Nitrogen excretion - Urea

Answer 12

Amphibians, turtles, mammals
- Less toxic
- Highly soluble but requires less water to excrete
- More costly (4-5 ATP)

Question 13

Nitrogen excretion -Uric Acid

Answer 13

Birds, lizards, snakes, terrestrial invertebrates, spiders, scorpions
- Lowest toxicity
- Lowest solubility requires lowest water to excrete
- Most costly