osmoregulation and excretion Flashcards
(70 cards)
1
Q
osmoregulation
A
regulation of water and ion balance in bodily fluids (e.g. lymph, blood, interstitial fluid, cytoplasm, haemolymph)
2
Q
excretion
A
elimination of toxic metabolic waste products e.g. CO2, H2O, nitrogenous compounds
3
Q
link between osmoregulation and excretion
A
osmoregulatory and excretory organs are often the same e.g. kidneys
4
Q
factors involved in osmoregulation
A
- solvent (water)
- solutes (ions)
- semi-permeable membranes
- diffusion
- osmosis
5
Q
isosmotic
A
- animal has the same osmotic concentration as the external environment (doesn’t truly exist as animals have different ions to the outside environment)
- equal exchange of water and ions between the organism and the external environment
6
Q
hyperosmotic
A
animal has a higher osmotic concentration than the environment (greater proportion of ions)
- organism needs to counteract the diffusion of water in and ions out using ion pumps (active transport)
7
Q
hyposmotic
A
- animal has a lower osmotic concentration than the environment (higher proportion of water)
- organism needs to counteract the diffusion of water out and ions in using ion pumps (active transport)
8
Q
excretory mechanism in many aquatic organisms
A
- eliminate ammonium via gills
- thin, highly permeable and vascularised
9
Q
ammonotelic organisms
A
organisms that can eliminate NH4+ straight away, quickest and most energy efficient. Most aquatic organisms
10
Q
excretory mechanisms in terrestrial organisms
A
- limited access to water, so NH4+ cannot be used as a waste product as it cannot be released immediately and is too toxic to be allowed to accumulate
- converted into a less toxic alternative so can accumulate to a degree
11
Q
ornithine cycle
A
process of deamination in vertebrates in liver, costly, requires water for elimination
12
Q
ureotelic animals
A
- urea excreted by kidneys
- include mammals, amphibians, some reptiles, cartilagenous fish
13
Q
uricotelic animals
A
- excrete uric ascid, solid and non toxic
- eliminated need for bladder with water
- excreted by hind gut, space and weight saving
- terrestrial arthropods, snails, snakes, birds, many reptiles
14
Q
osmoconformers
A
- primarily marine invertebrates
- animal conforms to the osmotic concentration of the environment
- blood/haemolymph is in an isoosmotic state
Some osmoconformers regulate solutes but maintain osmotic concentration (ionic
regulators)
15
Q
osmoregulators
A
- animals in brackish and freshwater environments
- animal regulates its body fluids independent to external environment
- maintains blood/haemolymph at a certain osmolarity
16
Q
marine invertebrates, osmolarity
A
- osmoconformers
- sea water and ECF (blood) isotonic (same osmolarity)
- ICF (cytoplasm) has less Na+ (toxic to cells) and more K+ to replace Na+ (cytoplasmic safe ion)
- ICF has same osmotic pressure as ECF and sea but different ion concentrations
- ICF ion concentration regulated by ion pumps
17
Q
estuarine/intertidal/brackish invertebrates osmolarity
A
- face changes in salinity, hostile environment, so primarily regulators
- all marine in origin
- some are osmoconformers e.g. mussels
18
Q
stenohaline
A
restricted to marine envrionments
19
Q
Mytilus edulis (Mussel)
A
- conform ECF
- regulate ICF
- have a ‘tidal clock’ so can use behavioural mechanisms to prepare for change in salinity such as closing shell first as it it less energetically expensive
- use amino acids to help prevent changes in ICF
- amino acids transported out of cell into blood and get broken down into ammonium (NH4+)
- release of NH4+ coupled with uptake of Na+
20
Q
factors affecting the movement of solutes and solvents across a semi-permeable membrane
A
- gradient
- membrane permeability (affects speed of diffusion)
- surface area
21
Q
ion pumps
A
- energetically expensive as constant movement of ions are needed to resist net movement of ions down a concentration gradient
- pumps often exchange more than one ion e.g. Na+/K+ ATPase
- symport pumps transport ions in the same direction
- antiport pumps transport ions in opposite direction
22
Q
water regulation
A
- water is small and polarised
- pumps cannot pump water molecules
- pumps transport ions and water moves passively via osmosis down a concentration gradient (low osmolarity to high osmolarity)
- ion pumps transport ions close to membrane, creating an area of localised high osmolarity, water diffuses in
22
Q
ammonium
A
- NH4+
- formed from deamination in the liver, breakdown of excess amino acids
- toxic, highly reactive and very alkaline
- highly soluble, so aquatic organisms can release it immediately into the environment down a concentration gradient through excretory organs
22
Q
nitrogen
A
- cannot be stored by body
- some in amino acid pool in blood
23
freshwater invertebrates
- all osmoregulators as freshwater is too dilute
- hypertonic blood
- highest level of membrane impermeability to ions and water
- primarily lose ions and gain water through gills (thin membrane, highly vascularised)
- use excretory systems to regulate ECF, produce lots of very dilute urine (Daphnia >200% body mass per day)
24
hyper-hyposmotic organisms
- can live in freshwater and marine environments
- very rare
- ECF hyperosmotic in freshwater and hyposmotic in sea water
- include crustaceans such as Chinese mitten crab, Palaemonetes (salt marsh shrimp) and Artemia (brine shrimp)
25
Artemia, hyper-hyposmotic organism
- can tolerate x3 strength of sea water
- salt glands on gills very good at osmoregulation
- shrimp drinks salt water and eliminates Na+ using salt glands, Cl- follows passively
26
terrestrial invertebrates
- limited access to water, need to be able to uptake it and minimise water loss
- many have behavioural responses to maintain moist environment
27
hygrophiles
live within moist environments
28
terrestrial inverts, water uptake
- can be fluid feeders, taking up water from eating or drinking (water can be obtained from metabolic catabolism of sugar)
- can take up water directly from moist air e.g. spiders, mites
29
water uptake in woodlice
- biramous appendages, legs are made up of two structures
- the top structure can absorb water from moist surfaces using capillary action
30
osmoregulatory organs in invertebrates
4 main types:
- contractile vacuoles (protozoans, sponges and also protists)
- nephridial glands (platyhelminthes)
- antennal/green glands
- malpigian tubules
31
contractile vacuoles
- protozoans and sponges
- one vacuole or multiple
- very small so difficult to monitor and study, the action of these vacuoles are only a hypothesis
- freshwater paramecium (protist) have them to maintain hyperosmotic ECF
- membrane bound, impermeable to water
- lined with radial canals
- surrounded my mitochondria (active)
- contains actin and myosin for contraction
32
action of contractile vacuoles
1. water flows into channels through osmosis
2. ions flow into channels
3. ions actively removed, water left behind
4. water flows into vacuole and collects
5. vacuole meets external membrane and contracts, expelling water from the cell
33
protonephridia
- earliest evolutionary type of nephridia, seen in platyhelminthes (flatworms)
- internal network of blind ending tubules which connect to
the environment via nephridophores
- tubules are nephridoducts
- cap cell on end of tubules with a large flagellum/a projecting into the tube
- the cap cell has interdigitations with the tube cell, creating filtration sites
- tubules lined with cilia
34
action of protonephridia
- flagella beats creating a negative pressure gradient at the end of the tube, drawing fluid within animal through digitations into tubule, filtering it
- cilia beat forcing fluid rapidly down length of the tubule, maintaining the pressure gradient and ensuring water doesn't diffuse back into the animal
- tubule is lined with ion pumps transporting ions back into the animal
- primary filtrate exits animal through nephridophore
35
metanephridia
- evolutionarily linked with protonephridia, more complex
- common to annelids, molluscs etc
- open tubules from coelomic cavity which exit at the exterior at a nephridiopore
- coelomic fluid passes into collecting tubule via nephrostome (ciliated funnel)
- selective reapsorbtion turns primary urine into secondary urine
- bladder stores urine
36
2 types of cap cells
- flame cells with several flagella
- solenocytes with a single flagellum
37
arthropods
- require different mechanism due to their
open circulatory system.
- Increase in complexity and reduction in the number required
- Aquatic crustaceans excrete NH4+ across their gills, they have antennal or green glands
- Terrestrial arthropods excrete mainly uric acid, urea etc
38
antennal/green glands
- eliminate divalent ions in aquatic crustaceans (NH4+ eliminated through gills)
- terminates at nephropore at base of 2nd (larger) antennae
- blind-ending at an end-sac (due to open circulatory system)
- lined with podocytes (same as mammalian kidney)
- opens into labyrinth (spongy and large surface area, reabsorbs ions)
- through canal into bladder
- only 2 needed as very selective, efficient and complex
39
action of antennal glands
- pressure generated in haemolymph causes water and ions in haelocoel to pass between podocytes (filtration) into end sac
- labyrinth reabsorbs ions
- through canal (some reabsorption) into bladder as secondary urine
- stored and released via nephropore
40
Carcinus, estuarine crab
- can tolerate a degree of freshwater
- is able to alter composition of urine to combat uptake of water (produces lots of very dilute urine when in freshwater)
41
malpigian tubules
- insects
- blind ending tubules which extend from mid-gut between mid and hind gut
- pumps that line tubules actively pull nitrogenous waste (soluble potassium urate) and other ions from haemolymph and water flows passively, moves into hindgut
- pumps in hind gut actively pumps K+ out into haemolymph, water follows passively
- K+ recycled, precipitation of potassium urate into uric acid (solid)
- constant recycling of water, no bladder needed, very effective at retaining water
42
vertebrate osmoregulatory organs, integument permeability
integument = tissue surrounding an organism's body
- permeability varies
- amphibians (mostly freshwater) permeable
- fish impermeable (scales)
- reptiles, birds, a few desert amphibians, terrestrial mammals impermeable
- secondary aquatic mammals impermeable
43
marine vertebrates, 3 main osmotic strategies
- osmoconformers, blood very similar in composition as seawater, hagfish
- ionoregulators but osmoconformers, blood isosmotically but ionically different, elasmobranchs (sharks), Rana, coelocanths etc
- osmoregulators, blood approximately 1/3 of sea water, ionically and osmotically different, teleosts
43
hagfish
- in deep sea, scarce food availability (yearly)
- can uptake nutrients across skin
- conserve energy by doing nothing, so does not waste energy by osmoregulating
- basal simple vertebrate group, only vertebrate with same osmotic strategy as invertebrates
44
hagfish, osmotic strategy
- ECF has slightly higher osmolarity than sea water
- slightly more Na+ and Cl-
- allows hagfish to slowly take up water passively to be able to eliminate heavy divalent ions (so has lower levels of divalent ions in ECF than blood)
- slightly regulate ECF but classed as osmoconformers
- regulates ICF
- kidney removes divalent ions in urine
45
elasmobranchs (sharks, skates and rays), coelocanths and Rana, osmotic strategy
- isosmotic but lower Na+ and Cl- levels in blood, osmoregulators
- top up with urea ( and other organic osmolytes, TMAO that offsets toxicity of urea by stabilising blood proteins) to bridge osmotic gap
- kidneys reabsorb urea
- no net movement of water as isosmotic
- passive uptake of Na+ and Cl-, eliminated by rectal gland, kidneys and maybe gills
46
marine teleosts (bony fish), osmotic strategy
- osmoregulators and ionoregulators
- hyposmotic, constantly lose water and gain salts through gills
- drink sea water as it is the only way to replace water loss
- 2 main osmoregulatory organs
- gills, eliminate Na+ and Cl- from blood (active transport, chloride cells)
- kidneys, remove divalent ions
47
marine teleosts, structure of gills
- contain alternating chloride and accessory cells
- highly effective and conserved
- apical membrane of chloride cell is highly permeable to Cl-
- basal membrane of chloride cell is highly convoluted, increasing surface area to increase number of ion pumps
- basal membrane has two different ion pumps, transport Na+ and Cl- into chloride cell and Na+ATPases transport Na+ back out of chloride cell into blood
- accessory cells can regulate the opening and closing of chloride cells depending on ion levels in ECF
48
marine teleosts, action of gills
1. active transport of Na+ and Cl- across the basal membrane into chloride cell
2. Na+ATPases actively transport Na+ back into the blood
3. very high levels of Cl- accumulate in chloride cell
4. Cl- diffuses out of highly permeable apical membrane into sea
4. generates local negative charge in surrounding sea water
5. Na+ is pulled through passively down gradient between accessory and chloride cells into the sea
49
freshwater vertebrates, osmotic strategies
- always hyperosmotic, constantly gain water and lose solutes
- do not drink water
- produce lots of very dilute urine
- kidneys reabsorb ions through active transport, high filtration rate
50
freshwater teleosts (bony fish), osmotic strategy
- Na+ and Cl- actively taken up from environment by gills (linked to CO2 elimination), similar mechanism to marine teleosts, but opposite action
- kidneys produce lots of very dilute urine, active reabsorption of ions
51
freshwater amphibians, osmotic strategy
- gain water and lose ions through skin (relatively permeable)
- integument, Na+ and Cl- actively taken up from environment (linked to elimination of CO2)
- kidneys produce lots of very dilute urine, active reabsorption of ions
52
terrestrial vertebrates, water loss
Main challenge is water loss/conservation
dehydration through:
- thermoregulation, evaporative cooling
- eliminating nitrogenous waste, urea
- ventilation, gases dissolves in fluid in respiratory organs
53
terrestrial amphibians, strategies to prevent water loss
- behavioural including seeking shade, nocturnal, living underground
- very short developmental time, tadpole stage synchronised to water availability
- eliminate nitrogenous waste using uric acid (solid)
- highly impermeable integument (not completely, still used for respiration)
- reduced metabolic rate
54
terrestrial amphibians water loss prevention strategies, Ranoidea spp.
- live in Australia
- burrows and secretes impermeable mucous cocoon during summer
- stores water up to 30% of body weight in bladder that can be reabsorbed
55
terrestrial reptiles, water conservation strategies
- dry scaly skin is very effective at reducing evaporative water loss
- eliminate nitrogenous waste as uric acid (solid)
56
terrestrial mammals water conservation strategies, Kangaroo rat
- adapted to very dry environment in southern USA and Mexico
- if air humidity >10% it does not need to drink water as so effective at reducing water loss
- behavioural strategies, nocturnal, lives underground in a burrow
- does not sweat or pant, relies almost entirely on behavioural thermoregulation strategies
- very dry faeces
- very concentrated urine (long loops of Henle)
- nasal countercurrent exchange system traps water leaving nose through exhalation
- eat seeds and grains, majority of water obtained is through metabolism
57
vertebrate kidney
- main osmoregulation organ of terrestrial mammals
- the are many nephrons in a kidney
- ability of the kidney to concentrate urine is linked to the animals environment
58
vertebrate kidney, the nephron
1. glomerulus
2. proximal convoluted tubule
3. loop of Henle
4. distal convoluted tubule
5. collecting duct
59
nephron, the glomerulus
- blood pressure forces compounds from the glomerulus (ball of capillaries) into the Bowman's capsule (blind ending tubule)
- filtrate is formed in the Bowman's capsule, including water, ions, urea, glucose, amino acids, H+
- large molecules are retained
60
nephron, proximal convoluted tubule
- active reabsorption to recapture ions, water and valuable nutrients (active transport, facilitated diffusion, cotransport)
- some active secretion into the PCT e.g. drugs and toxins
61
nephron, loop of Henle
- countercurrent concentrating system
- ascending limb is impermeable to water, Na+ and Cl- is pumped out, increasing the osmolarity of the medulla and decreasing the osmolarity of the ascending limb
- descending limb is permeable to water and has low permeability to ions, water moves out to the high osmolarity in the medulla
62
nephron, distal convoluted tubule
- reabsorption of salts, Ca2+ and regulation of blood pH
63
nephron, collecting duct
- ADH/vasopressin released by posterior pituitary (regulated by osmoreceptors in hypothalamus)
- controls permeability of collecting duct
- absence = permeability decreased, water cannot pass out of filtrate, dilute urine formed
- presence = more permeable, water reabsorbed, concentrated urine formed
64
different types of nephrons
- concentrating ability depends on how long the loop of Henle is, how much it extends into the medulla
- juxtamedullary nephrons have long loops of Henle
- cortical nephrons have short loops of Henle
- desert rodents etc need concentrated urine so have lots of juxtamedullary nephrons
- beavers and pigs need dilute urine so have lots of cortical nephrons
- humans have a mixture of both
65
polar teleosts
- hyposmotic blood means it has a higher freezing point than the sea water around it
- have antifreeze glycopeptides in blood
- kidneys do not operate via ultrafiltration or antifreeze proteins would be filtered out, so glomeruli are absent
- eliminate ions through active secretion
66
marine mammals
- hypotonic blood
- no free freshwater so water limited
- baleen/mysticeti whales eat marine invertebrates (high salt load)
- odontoceti/ toothed whales eat marine vertebrates (less high salt load)
- both produce very concentrated urine, hyposmotic to blood and sea water
- very long loops of Henle
67
marine reptiles
- hypotonic blood
- no loops of Henle, kidney doesn't eliminate salt, can't produce very dilute urine
- eat marine invertebrates, corals and seaweed (high salt load)
- have salt glands very similar to marine teleosts (highly conserved)
- turtles have salt glands in eyes, crocodiles have salt glands on tongue, iguanas (and birds) have salt glands in nasal passage
