Topic 5e - Excretory systems

Question 1

Wastes…?

Answer 1

CO2
undigested food
waste prods of cellular metabolism (mainly nitrogen-containing compounds)

Question 2

Differences between elimination & excretion…?

Answer 2

elimination - undigested foods passed from alimentary canal via anus (faeces)
excretion - digested food waste, filtered out of blood, urine

Question 3

Form of nitrogenous waste depends on…?

Answer 3

taxonomic affiliation & habitat
eg. ammonia -> water soluble aquatic organisms
urea -> most mammals
uric acid -> water insoluble -> insects, birds, reptiles

Question 4

Properties of ammonia…?

Answer 4

very water-soluble but toxic

Question 5

Properties of urea…?

Answer 5

less water-soluble & less toxic & requires energy for conversion

Question 6

Properties of uric acid…?

Answer 6

practically water-insoluble & requires most amount of energy for conversion

Question 7

What are protonephridia? Function?

Answer 7

branching tubules extend throughout extracellular fluid (flatworms) -> excreted via pore
mainly get rid of excess water

Question 8

What are malpighian tubules?

Answer 8

• branching tubules extend into haemolymph -> wastes & nutrients flow into them via active transport & diffusion -> nutrients removed from urine -> back into haemolymph. Urine mixes with faeces -> ejected together
  ONLY IN INSECTS!

Question 9

Excretory system in earthworms & molluscs…?

Answer 9

Nephridia - tubules extending into ECF -> cilia move ECF into tubule & cells remove salts & nutrients from fluid -> wastes concentrated in water (urine) -> via nephridiopore

Question 10

Functions of kidneys…?

Answer 10

excretion of cellular waste
regulating [ionic] in blood
blood pH
water content of blood
retaining nutrients (glucose, AAs)
secreting sub's that regulate BP & O2 levels
found in vertebrates

Question 11

Excretory structures…

Answer 11

kidneys -> ureters -> bladder -> urethra -> excretion

Question 12

Outer to inner layers of kidney…

Answer 12

renal cortex, renal medulla, renal pelvis

Question 13

Filtration occurs where?

Answer 13

water, nutrients, wastes from glomerular capillaries -> Bowman’s capsule

Question 14

Tubular reabsorption occurs where?

Answer 14

proximal tubule - most water & nutrients reabsorbed back into blood

Question 15

Tubular secretion occurs where?

Answer 15

wastes transported into proximal & distal tubules from blood

Question 16

Concentration occurs where?

Answer 16

Loop of Henle produces salt concentration gradient in extracellular fluid. In collecting duct, urine may become more concentrated than blood as water leaves by osmosis

Question 17

Re. maintenance of homeostasis, what regulates blood water content?

Answer 17

antidiuretic hormone (ADH)

Question 18

Re. maintenance of homeostasis, what regulates BP?

Answer 18

renin-angiotensin
  - ++ absorption of Na+
  - ++ADH release
  - constricts arterioles
=> increases blood volume via fluid retention -> increases BP

Question 19

Re. maintenance of homeostasis, what regulates blood oxygen levels?

Answer 19

erythropoietin

Question 20

Adaptation to arid conditions?

Answer 20

Longer loops of Henle -> more concentrated urine (14x that of blood)

Question 21

Adaptation to wet environments?

Answer 21

short loops of Henle -> (2x osmolarity of blood)

Question 22

Adaptation to intermediate environments?

Answer 22

mix of long & short loops of H (humans 4x osmolarity)

Question 23

Adaptation to hypotonic conditions (freshwater)?

Answer 23

continual osmosis via gills (water gain) & salt diffuses out via gills
lots of very dilute urine produced

Question 24

Adaptation to hypertonic conditions (saltwater)?

Answer 24

continual osmosis via gills (water loss) & salt diffuses in via gills
salt actively exported by gills, drink seawater
small amounts of urine produced

Question 25

Which animals use ureo-osmoregulation?

Answer 25

sharks & rays