Ch. 14 Non-Mammalian Kidneys/Other Osmoregulatory Organs Flashcards
marine hagfish kidneys
nephrons have glomeruli but no tubules
Bowman’s capsules empty directly into collecting ducts
kidneys of freshwater teleosts whose bodies are hyperosmotic
produce large volumes of dilute urine
larger and more glomeruli
kidneys of marine teleosts whose bodies are hypoosmotic
have no glomeruli or bowman’s capsules
produce small volumes urine by secretion
elasmobranch Raja erinacea kidney
has countercurrent system but kidney is different
retains urea and does not make concentrated urine
what 3 animals have glands that secrete salt
elasmobranches
marine bids
some reptiles
are marine elasmobranches hypo or hypertonic to seawater, and what is their sodium content in comparison?
slightly hypotonic
sodium is much lower than seawater – continual influx of NaCl
elasmobranch rectal gland purpose
makes and excretes a concentrated salt solutions to regulate extracellular fluid volume
elasmobranch rectal gland structure
lots of blind-ended tubules surrounded by blood capillaries
tubules drain into a duct –> intestine near the rectum
the fluid made by the elasmobranch rectal gland has a slightly higher ______ content than seawater but is ___osmotic to blood plasma
salt,-iso-osmotic
the elasmobranch blood is slightly ____osmotic to seawater and contains
hyperosmotic
lots of urea and TMAO
hyposmotic amount of salt
do urea and TMAO appear in elasmobranch rectal gland excretions?
no, just NaCl
how does the elasmobranch rectal gland work
Apical - Cl- channel into seawater
Basolat - very folded with lots of Na/K pumps and Na/2Cl/K cotransport
Cl moving into seawater causes transmembrane potential that moves Na out paracellularly against gradient
where is the salt gland located in birds/reptiles
depressions in the skull above the eyes
structure of marine bird salt glands
many lobes with secretory tubules and a central canal
duct runs through the beak and into the nostrils
marine bird salt gland secretory epithelial
like typical salt secreting epithelium
lots of Na/K pump in basolat and Na/2Cl/K cotransport
Cl- channels in apical
Cl- moving out causes Na to move out paracellularly against Na gradient
is the salt solution in the bird salt glands hyper or hypo osmotic to blood
hyperosmotic
the birds that make the most concentrated salt solution have…
largest secretory cell and a long paracellular channel between cells
is there a countercurrent system in bird salt glands
yes
will ouabain inhibit bird salt glands
yes, lots of mitochondria there to make ATP to drive Na/K pumps
what stimulates bird salt gland production
raise in extracellular fluid volume and salt content
why can’t mammals drink seawater even though we have salt-secreting cells in the ascending limb of the loop of Henle
arrangement of cells doesn’t allow producing a hypertonic salt soln that can be excreted
in teleost fishes, what major function do gills perform
managing osmotic stress
structure of teleost gills
large epithelium for gas exchange/salt transport
chloride cells invaginated in folded basolat w/ lots of mito
mucous cells form boundary btw epithelium and seawater
teleost chloride cell salt transport method (and Ca)
high level of Na/K pump and Na/2Cl/K cotransporter in basolat
Cl channels in apical memb
Cl out causes Na out paracellularly
in marine teleosts does the transport of salt occur against an osmotic gradient?
yes, so no water follows
uptake of salt in freshwater fish gills
Apical - H+ pump puts H+ into seawater, Na channels bring Na in
Basolat - Na/K pump puts Na in blood and K cycles through channels
chloride cells in gill epithelium of freshwater fish
uptake Ca from water
anion transporter in apical
lots of H+ pumps
migrating fish from fresh to seawater adaptations
proton pump that brings in NaCl down-regulated
rise in body/plasma Na causes more cortisol and growth hormone levels
hormones make chloride cells and insert into basolat –> more active Na/K pump and NaCl secretion
migrating fish from sea to freshwater
paracellular gaps btw chloride and accessory cells close causing less loss of NaCl
prolactin increases –> lower chloride cells and apical pits to disappear
Na/K pump activity falls
upregulate proton pump
what invertebrates make concentrated urine
insects
spiders
urine in mollusks and crustaceans
like humans, high [ ] = excretion (inulin, glucose) and others reabsorbed
depends on bp
phlorizin drug that blocks glucose transport in mollusks and crustaceans
glucose still appears in urine
glc must enter urine as a part of filtrate
in crayfish what is the major organ of osmoregulation
antennal gland with a coelomosac (like glomerulus)
downside of a filtration-reabsorption system like kidney
high energy cost
needs high intake of salts
do insects have a large surface to volume ratio?
yes
places a lot of osmotic demand
can the locust regulate the ionic strength of its hemolymph?
yes
during dehydration the hemolymph decreases by 90% but ionic concentration is maintained
the osmoregulatory system of locusts and insects consists of the ___________ tubules and _______
Malpighian tubules, hindgut (ileum colon and rectum)
the closed ends of the long thin Malpighian tubules lie in the _________
hemocel – hemolymph containing body cavity
the Malpighian tubules empty where
alimentary canal at the junction of the midgut and hindgut
pathway of secretion through the Malpighian tubules
tubules –> hindgut where it is dehydrated –> rectum –> concentrated urine through anus
the presence of a ________ system for respiration in insects diminishes the importance of an efficient circulatory system
tracheal
do the Malpighian tubules get a direct arterial blood supply?
no, they are surrounded by hemolymph at equal pressure
b/c no pressure, no filtration system
urine formation by Malpighian tubules
KCl and NaCl from hemocoel into lumen with waste like uric acid
most NaCl and KCl returned to hemolymph across rectal wall
ionic editing occurs in hindgut
what ion drives the formation of urine in the Malpighian tubules
K+, other substances follow passively
hindgut of locus Schistocerca
Apical - Cl pump into cell, K channel into cel, Na uptake + aa uptake OR ammonium excretion, H+ pump into urine
Basolat - K and Cl channels into blood, Na/K pump, Cl/bicarb antiport moves Cl into cell and bicarb into hemolymph
mealworm beetle Tenebrio countercurrent system
Malpighian tubules touch hemocel
perirectal space in middle
rectal lumen and anus below perirectal space
mealworm beetle Tenebrio mechanism
water drawn osmotically from rectum into Malpighian tubules by KCl gradient from active transport
highest osmolarity by anus
urine:blood osmolarity of 10:1
feedback mechanism in blood sucking Rhodnius
after sucking blood, 2-3min go by and Malpighian tubules increase secretion by 1000x
artificial bloating doesn’t cause this
diuretic hormone in response to ingested blood – serotonin?
when aa are catabolized the aa group NH2 is released (_________) or transferred to another molecules for reuse…aa not salvaged for resynthesis must be…
deamination
dissolved in water and excreted to avoid a toxic rise in nitrogenous waste
most excess nitrogen is excreted as what 3 things
ammonia
urea
uric acid
is ammonia more toxic than urea or uric acid
yes
how does excretion of ammonia occur
diffusion
requires large volume of water
urea excretion
requires less water than ammonia but needs ATP to synthesize
uric acid is excreted as what
not soluble so white pasty precipitate of bird poop
what determines the nature of nitrogen excretion
availability of water
aquatic excrete across gills
terrestrial animals excrete urea or uric acid via kidneys
ammonotelic
excrete nitrogenous waste as ammonia
teleosts and aquatic invertebrates
which form of ammonia are cell membranes permeable
NH3
not NH4+
how do teleosts excrete ammonia
H+ and CO2 excretion cause acidification of water next to gill surface
this traps NH3 as NH4 as NH3 passively diffuses out of gills
how is a small amount of ammonia excreted in mammalian kidneys
glutamine released from liver –> blood –> kidney is deaminated by kidney tubule cells and ammonia goes into the lumen
it takes up a proton –> NH4 which cannot diffuse out
high ammonia levels in aquatic environments are toxic, especially at high __
pH
impairs excretion so glutamine may be stored instead
fishes also downregulate ammonia synthesis
toxicity of ammonia
changes tertiary structure of proteins
disrupts ion transport b/c substitutes as K+
squids shrimp and tunicates do what to ammonium ions
collect it in acidified chambers and substitute it for Ca and Mg
urea-excreting (ureotelic) animals
excrete nitrogenous waste as water-soluble urea
vertebrates use ornithate-urea cycle
teleosts/invert use uricolytic pathway
ornithate-urea cycle of vertebrates
2 NH2 and 1 CO2 added to ornithine to make arg
arginase removes urea to regenerate ornithine
how do elasmobranches use ornithate-urea cycle
use the urea as an osmolyte to inc body osmolarity
excrete urea across gills
uricolytic pathway
urea made from uric acid from transamination of asp or na metabolism
gout
buildup of insoluble uric acid crystals
uric acic-excreting animals (uricotelic)
birds, reptiles, arthropods
removes 4 N atoms per/uric acid
how is uric acid excreted
proximal tubule of nephron via organic anion secretory mechanism
in birds competes for transport in kidney with PAH
