Lecture 14: Waste disposal Flashcards
why do you have to wee when you stand in a pool of water & are cold?
artery walls stretch & hormones are released
Proteins are also digested for… (or converted to ….)
-digested for energy
-converted to fat & carbohydrates.
When used for energy or converted, the NH2 (amino) group if removed.
-N containing compounds are toxic and must be removed
-type of waste produced depends on organism
What sort of animals produce ammonia
Aquatic invertes, bony fishes, aquatic amphibians
Why is ammonia produced???
- Is toxic; can’t exceed [0.05mmol/l]
- free to make
- highly soluble in H2O
- Also eliminated by aquatic orgs (in H2O) and so effective toxicity reduced
- small molecule so diffuses quickly across gills
Evolution of terrestrial life required a better way to get rid of..
Nitrogen. (BECAUSE OF AMMONIA)
what animals produce Urea & WHY
- mammals, most amphibians, cartilaginous fish.
- Less toxic than ammonia.
- requires limited access to H2O (to excrete 1g N = 50ml H2O)
- requires energy: 1.5ATP/N
what animals produce Uric acid & WHY
- Birds, insects, reptiles, some amphibians
- insoluble in H2O
- Excreted as semi-solid which allows org to conserve water which is possible because uric acts isn’t toxic. (1g N required 1ml H2O)
- requires energy: 5 ATP/N
generalised excretory organ in insects
Malpighian tubules
generalised excretory organ in: protozoan
contractile vacuoles
protozoan is a
a single-celled microscopic animal of a group of phyla of the kingdom Protista
generalised excretory organ in: vertebrates
Kidneys
generalised excretory organ in invertebrates
Nephridia
name 4 specialised excretory systems:
- salt glands
- gills
- liver - porphyrin
- rectal glands
3 steps in metabolic waste disposal
- filtration
- reabsorption
- secretion
– These processes involve osmosis, active transport, selectively permeable membranes
– Blood needs to be brought into close contact with structures
– Then filtrate excreted
filtration:
blood fluids collected; some solutes &
H2O returned to body, some stay in the “filtrate”
reabsorption:
Selective transport of needed filtered substances back to tissue fluid/blood to be circulated in body
secretion:
Filtrate joined by un-needed substances (toxic, excess) from the blood and tissue fluid
the human excretory system at 3 size scales: 1
- -posterior vena cava
- renal artery & vein
- aorta
- ureter
- urinary bladder
- urethra
- Kidney
the human excretory system at 3 size scales: 2
(Kidney)
- renal medulla
- renal cortex
- renal pelvis
- ureter
the human excretory system at 3 size scales: 3
cortex:
- - (proximal & distal) convoluted tubules
- -glomeruli & Bowmans capsule
- medulla:
- -collecting ducts
- -long loops of henle (Ascending + Descending)
only ___ have loops of Henle
mammals & birds
- in humans 80% of nephrons are short and located within the cortex. 20% have long loops of Henle that extend into the medulla
- -allow production of hypertonic urine to conserve water
countercurrent multiplier system: what does each word mean ~ kinda
countercurrent: tubule fluid in descending limb flows in opposite direction from ascending limb
Multiplier: ability of system to create cone gradient (active & passive)
Loops increase solute potential of surrounding tissue fluid setting up a conc gradient
steps through the nephron and collecting duct
1) blood vessel to bowmans capsule
2) proximal tubule (HCO-3, NaCl, K+, H2O, Nutrients leave, H+ & NH3 Enter)
3) descending limb of loop of Henle (H2O leaves)
4) thin segment of ascending limb (NaCl leaves)
5) distal tubule (NaCl out, H2O out, HCO-3 out, K+ in, H+ in)
6) Collecting duct (Nacl out, Urea + H2O out)
DECREASING BF (body fluid) osmolarity without changing salt -stimulus: Blood osmolarity increases above set point (e.g. due to dehydration or eating salty food)
1) INCREASED extracellular fluid osmolarity activates osmoreceptors cells in the hypothalamus
2) Increased secretion of ADH from the pituitary
3) Increasing water permeability in the distal convoluted tubule & collecting duct
4) Increased reabsorption of water without salt
5) Decreased osmolarity
INCREASING BF (body fluid) osmolarity without changing salt. Stimulus: Low blood volume of blood pressure (e.g. due to dehydration or loss of blood)
1) drop in Na+ concentration causes special cells near the glomerulus to secrete the enzyme renin leads to Angiotensinogen leading to..
2) Angiotensin ||:
- Increases Na+ and water reabsorption
- causes vasoconstriction to increase blood pressure
3) Aldosterone: Increases Na+ and water reabsorption
Insects and their waste
- relatively higher SA:V ratio
- takes more water to produce ammonia
- high;y efficient (most successful terrestrial animals)
- open circulatory system
- – no high pressure filtering
- malpighian tubules
how many malpighian tubules do insects have?
Anywhere from 2 (coccids; scale insects) to 250 (desert locust), depending on species
what is this describing: A blind-ended tube with walls exactly 1 cell thick
Malpighian tubules
where do Malpighian tubules float and open into
in haemolymph. Open into handgun
production of waste in insects through Malpighian tubules
- Mts collect H2O & uric acid from blood (haemolymph)
- Epithelium pumps solutes from haemolymph to tubule lumen
- empty into midgut
- H2O & useful materials reabsorbed by handgun (rectal pads) but wastes remain in handgun to be excreted
- so most salt is reabsorbed from rectum
- water follows by osmosis
- nitrogenous wastes eliminated with faeces
