Ch.44: Osmoregulation and Excretion
anhydrobiosis
"life without water" a dormant state when their habitats dry up
nitrogenous breakdown products of proteins and nucleic acids are significant
*
nitrogenous waste and energy budget have to be balanced
*
what is the osmoregulation for the resting metabolic rate of: -fish -brine shrimp -terrestrial animals
-5% -30% -0.5 mmol
what do flame bulbs consist of?
-a tubule cell and a cap cell. -each flame bulb has a tuft of cilia projecting into the tubule
metanephridia
-earthworms (little bit more advanced) -excretory organs that collect fluid directly from the coelom.
what are the key functions of most excretory systems?
-filtration -reabsorption -secretion -excretion
protonephridia
-in flatworms (always have these) -form a network of dead-end tubules. Tubules, which are connected to external openings, branch throughout the flatworm body, which lacks a coelom.
malpighian tubules
-insects and land arthropods -remove nitrogenous wastes and also function in osmoregulation
in what other species are protonephridia found?
-rotifers -mollusc larvae -lancelets
what anatomical features and behavioral adaptations do desert animals have?
-they are nocturnal -they have water storage (camel humps) -they are elevated from the desert floor
what is the process of from blood filtrate to urine?
1. Proximal Tubule 2. Descending limb of the loop of Henle 3. Ascending limb of the loop of Henle 4. Distal Tubule 5. Collecting Duct
the amount of energy differs based on?
1. how different the animals osmolarity is from its surrounding 2. how easily water and solutes move across the animals surface 3. the work required to pump solutes across the membrane
what is the osmolarity of human blood?
300 mOsm/L
kidney can produce ______ concentrated urine
4x
what is secreted from the proximal tubule?
H+ and NH4+
what are the different forms that animals excrete nitrogenous waste?
NH3 (ammonia), uric acid, and urea
what are the two primary solutes affecting osmolarity?
NaCl and Urea
what surrounds the internal opening of each metanephridium?
a ciliated funnel
trehalose
a disaccharide that seems to protect the cells by replacing the water that is normally associated with proteins and membrane lipids.
urea
a nitrogenous waste product of protein and nucleic acid metabolism
filtrate
a solution made up of small molecules, like salts, sugars, amino acids, and nitrogenous waste, that can cross the membrane
what do vampire bats have?
a specialized kidney
how many nephrons does a kidney have and why?
about a million nephrons to filter
what is required by animals for this form of waste?
access to lots of water because ammonia can be tolerated only at very low concentrations
how do invertebrates get rid of ammonia?
across the whole body surface
what are the advantages and disadvantages of urea?
advantage: it is very low toxicity disadvantage: it cost a lot of energy
who are osmoconformers?
all osmoconformers are marine animals, but not all marine animals are osmoconformers
what are the challenges freshwater animals face?
an environment that threatens to dilute their body fluids.
trimethylamine oxide (TMAO)
an organic molecule that protects proteins from damage by urea
how do the vampire bats prevent blood clotting?
anticoagulants in the bats saliva prevent the blood from clotting
what animal is ammonia excretion most common in?
aquatic species
how else do reptiles excrete waste?
as uric acid
excretion
bad stuff goes out of the body -the altered filtrate (urine) leaves the system and body
secretion
bad things go out (active transport) -other substances, such as toxins and excess ions, are extracted from body fluids and added to the contents of the excretory tubule
glomerulus
ball of capillaries
examples of euryhaline osmoconfomers?
barnacles, tidal animals -alternately submerged and exposed by the tides
why does the vampire feed so much when it finds a prey? (often more than half its body mass)
because it has to search long and fly far to find a prey
why is ammonia so toxic?
because its ion, ammonium, can interfere with oxidative phosphorylation
osmoconformers
being isoosmotic with your surroundings -change osmolarity to match environment
guano
bird droppings. A mixture of white uric acid and brown feces
other than urea, what else does a sharks body contain?
body fluids that also contain TMAO
examples of euryhaline osmoregulators?
bull shark, salmon
how is filtrate processed into urine?
by blood pressure. It drives the whole system
how do freshwater animals solve the problem of water balance?
by drinking almost no water and excreting large amounts of very dilute urine
how do birds conserve water if they have shorter loops of henle?
by excreting uric acid (guano) instead of urea
how do most excretory systems produce urine?
by refining a filtrate derived from body fluids
flame bulbs
cap the branches of each protonephridia
collecting duct
carries filtrate through the medulla to the renal pelvis reabsorption of solutes and water (under hormonal control)
other reptiles have only cortical nephrons but reabsorb water from wastes in the _______?
cloaca
each segment of an earthworm has metanephridia, that are immersed in?
coelomic fluid and enveloped by a capillary network
examples of stenohaline animals?
conformers
amphibians on land:
conserve body fluid by reabsorbing water across the epithelium of the urinary bladder
Energy is expended to actively transport NaCl from the filtrate in the upper part of the ascending limb, how?
countercurrent multiplier system: expend energy to create concentration gradients. -maintain high salt concentration in the kidney, enabling the kidney to form concentrated urine.
Bowman's capsule
cup shaped swelling that surrounds the glomerulus
in the proximal tubule, filtrate volume _________ as water and salt are reabsorbed, but __________ remains the same HOW?
decreases; osmolarity -a large amount of water and salt is reabsorbed from the filtrate as it flows through the proximal tubule in the renal cortex.
what is an example of an osmoconformer?
dungeness crab. It excretes sodium to maintain its balance
what is the problem with ovipary?
eggshells are not permeable to liquids so the soluble nitrogenous waste released by an embryo would be trapped within the egg and could accumulate to dangerous levels leading to death
what must osmoregulators expend to maintain osmotic gradients?
energy
proteins are nucleic acids are used for ______ and converted to _________
energy; carbohydrates
marine animals need to eliminate wha to survivet?
excess salt
marine fishes gain______ and lose _________
excess salt from their surroundings; water
freshwater fishes excrete?
excess water continuously
amphibians in the water:
excrete dilute urine while their skin accumulates certain salts from the water by active transport (lots of nephrons)
what body coverings help terrestrial animals prevent water loss?
exoskeleton, skin, fur, shell
juxtamedullary nephrons
extend deep into the medulla
where do malpighian tubules extend from?
extend from dead-end tips immersed in hemolymph to openings into the digestive tract
filtration
filters body fluid. Big stuff stays behind, small stuff and water push through. -excretory tubule collects a filtrate from the blood. Water and solutes are faced by blood pressure across the selectively permeable membranes of a cluster of capillaries and into the excretory tubule
what happens to the filtrate in the ascending limb of the loop of Henle?
filtrate becomes increasingly dilute
what step is the malpighian tubule missing?
filtration
what happens in metanephridia when the cilia beat?
fluid is drawn into a collecting tubule, which includes a storage bladder that opens to the outside
what do marine vertebrates/some marine invertebrates constantly lose during osmosis?
fresh water is lost; it leaves quickly
Because freshwater animals have a higher osmolarity than their surroundings, what problems do they face?
freshwater animals face the problem of of gaining water by osmosis and losing salt by diffusion
where is urea excreted?
from the kidney through the urine
kidney function
functions in both osmoregulation and excretion
what happens in humans where there is a build up of uric acid?
gout; a painful joint inflammation caused by deposits of uric acid crystals
is uric acid production expensive?
hell yeah
what are excretory systems central too?
homeostasis
what are the main differences in kidneys of different animals?
how many juxtamedullary nephrons and length of the loop of Henle
marine fishes are _______ to surroundings
hypoosmotic
water flows by osmosis from a __________ solution to a _____________ solution
hypoosmotic; hyperosmotic
why is osmoregulation important?
if there is too little water, the cell will shrink if there is too much water, the cell will burst balance is key
renal medulla
inner portion of the kidney
who excretes uric acid?
insects, land snails, and many reptiles including birds
what does osmoregulation involve?
involves concentration gradient across the plasma membrane for both solute and water -active transport and facilitated transport
what happens to the filtrate in the descending limb of the loop of Henle?
it becomes more concentrated
what makes a vampire bats kidney so efficient?
it can excrete large amounts of dilute urine so the bat can drop mass and be able to fly after feeding
what does the initial filtrate produced in browman's capsule contain?
it contains salts, glucose, amino acids, vitamins, nitrogenous wastes and other small molecules
why is excretion so important?
it gets rid of ammonia
what does HCO3 do?
it is a buffer in the blood
why is it better to be an osmoconformer?
it is less taxing energetically to be an osmoconformer
how do freshwater animals get back the salt they lose by diffusion and in the urine?
it is replenished by eating and also replenish salts by uptake across their gills
what does the ascending limb of the loop of Henle lack?
it lacks water channels- impermeable to water
what has been discovered in ahydrobiosis animals?
large amounts of sugars; in particular a disaccharide called trehalose
how much water is needed relative to ammonia?
less
how toxic is it relative to ammonia?
less toxic
stenohaline
live in a narrow environment. They cannot tolerate substantial changes in external osmolarity
long v. short loops of henle
longer the loop, the more concentrated the urine
filtration rates in marine fishes?
low and very little urine is excreted
do sharks have a lower or higher internal salt concentration?
lower
what do the thin and thick segment of the ascending limb of the loop of Henle do?
maintain osmolarity of the interstitial fluid in the medulla
as the filtrate passes through the proximal tubule, what becomes concentrated?
material (urea) to be excreted
how are molecules transported in the proximal tubule?
molecules are transported actively and passively from the filtrate into the interstitial fluid and then capillaries
who excretes urea?
most terrestrial animals
what is movement of water driven by in the descending limb of the loop of Henle?
movement of water is driven by the high osmolarity of the interstitial fluid, which is hyper osmotic to the filtrate (osmosis)
is uric acid toxic?
nah
marine fishes have fewer and smaller?
nephrons (and lack distal tubule)
are marine sharks hypoosmotic to seawater?
no
liquid level in uric acid?
not really that much
what are marine animals usually?
osmoconformers; osmolarity same as the sea water
isoosmotic
osmolarity on both sides. No net movement of water
what are many marine vertebrates and some marine invertebrates?
osmoregulators; for them the ocean is a strongly dehydrating environment
how does water enter and leave the cell?
osmosis
renal cortex
outer portion of the kidney
osmoregulation
process by which animals control solute concentrations and balance water gain and loss within a narrow range
reabsorption
reabsorbs the good things (active transport) -the transport epithelium reclaims valuable substances from the filtrate and returns them to the body fluids
proximal tubule
reabsorption of ions, water, and nutrients take place in the proximal tube.
descending limb of the loop of Henle
reabsorption of water continues through water channels formed by aquaporin proteins -energy consuming machine
cortical nephrons
reach only a short distance into the medulla
distal tube
regulates the K+ (secretion) and NaCl (reabsorption) concentrations of body fluids
how does salt diffuse into a sharks body?
salt diffuses into their bodies from water through their gills (especially)
ascending limb of the loop of Henle
salt, but not water, is able to diffuse from the tubule into the interstitial fluid
why are sharks not hypoosmotic to seawater?
shark tissue contains high concentrations of urea
in comparison to mammals, how long are birds loops of henle?
shorter
marine fishes have __________ kidney glomeruli
small or lack
what can be actively secreted into the filtrate from the proximal tubule?
some drugs and toxins
what must be actively transported to maintain homeostasis in marine animals that are osmoconformers?
specific solutes because the concentrations in sea water and in the animal differ
osmosis
spontaneous movement of water from higher to lower concentration across a semipermeable membrane
what type of environment do osmoconformers live in?
stable environments
example of anhydrobiosis
tardigrades: in their active state they are 85% water but can dehydrate to less than 2% water and survive in an inactive state for a decade or more
what happens during filtration in the flame bulb?
the beating of the cilia draws water and solutes from the interstitial fluid through the flame bulb, releasing filtrate into the tubule network
what are the osmoregulatory problems on freshwater animals?
the body fluids of freshwater animals must be hyper osmotic because animal cells cannot tolerate salt concentrations as low as that of lake or river water
what in the distal tube contributes to pH regulation?
the controlled movement of H+ (secretion) and HCO3- (reabsorption)
what is key to water conservation in terrestrial animals?
the juxtamedullary nephron
where is it produced in vertebrates?
the liver. produced when ammonia and carbon dioxide combine in the liver
hypoosmotic
the more dilute solution
osmolarity
the number of moles of solute per liter of solution -how we measure osmosis -determines the movement of water across a selectively permeable membrane
excretion
the process that rids the body of nitrogenous metabolites and other metabolic waste products
what happens to the filtrate after is been released into the tubule network?
the processed filtrate moves outward through the tubules and empties as urine into the environment.
what is an additional adaptation that some terrestrial insects have for water balance?
the rectal ends of their gut enables water uptake from the air. (usually need humidity, but fleas can do it at low humidity)
hyperosmotic
the solution with the higher concentration of solutes
what does the malpighian tubule do instead of filtering?
the transport epithelium that lines the tubules secrete certain solutes, including nitrogenous wastes, from the hemolymph into the lumen of the tubule. Water follows the solutes into the tubule by osmosis, and the fluid then passes into the rectum. THEN most solutes are pumped back into the hemolymph, and water reabsorption by osmosis follows.
if there are more juxtamedullary nephrons what does this mean in terms of urine?
the urine is more concentrated
what do salmon that migrate to the ocean do?
they acclimatize; they produce more of the steroid hormone cortisol. As a result salmon excrete excess salt from their gills and produce only small amounts of urine
what is an essential part of the vampire bats adaptations to their unusual food source?
they alternate rapidly between producing large amounts of dilute urine and small amounts of very hyper osmotic urine
what about animals that live in temporary ponds?
they can lose almost all their body water and survive. They enter anhydrobiosis
why do humans consume more food than a kangaroo rat?
they consume more food because they use more energy and then they excrete more waste
how do the different forms of nitrogenous waste differ from one another?
they differ in toxicity and the energy costs of producing them
why are excretory systems central to homeostasis?
they dispose of metabolic waste and control body fluid composition
how do vertebrate/some invertebrate fish balance the water loss?
they drink large amounts of sea water and get rid of excess salt through their gills and kidneys.
what do animals that have ovipary do about waste?
they excrete uric acid as a waste because it precipitates out of solution and can be stored within the eggs as a harmless solid left behind when the animal hatches
ammonia is very toxic, so what do some animals do before they excrete it?
they expend energy to convert it to less toxic compounds; they add fluid to dilute it
how do terrestrial animals get water and where do they lose it?
they get water from food and freshwater sources and it is lost by feces, urine, and perspiration
what do freshwater animals do in order to survive?
they need to conserve solutes and absorb salts from their surroundings
what do salmon in in freshwater do?
they osmoregulate; they produce large amounts of dilute urine and take up salts from their dilute environment through their gills
what do excretory systems do?
they regulate solute movement between internal fluids and the external environment-water balance
why are enzymes important?
they remove N2 in the form of NH3
what do the salts, urea, TMAO, and other compounds in a sharks body maintained in the body fluids result in?
they result in an osmolarity very close to that of seawater -for this reason, sharks are often considered osmoconformers
what do animals that spend half the time in water and half the time out of water do?
they switch between excreting ammonia and excreting urea -ex: frogs
what do salmon and other euryhaline fishes that migrate between freshwater and seawater undergo?
they undergo dramatic changes in osmoregulatory status
why do endotherms produce more nitrogenous waste than ectotherms?
they use energy at higher rates and eat more food therefore producing more waste
NaCl transport in the ascending limb of the loop of Henle?
thin segment (passive) and thick segment (active)
the initial filtrate produced in Bowman's capsule has concentrations that are the same as?
those in the blood plasma
osmoregulator
to control internal osmolarity independent of that of the external environment
what do kidneys consist of?
tubules
the ______ and ______ of an animals waste products affect its water balance why?
type; quantity because metabolic waste must be dissolved in water to be excreted in from the body
what do insect and land arthropods excrete?
uric acid, mainly insoluble, that are eliminated as nearly dry matter along with feces
in the collecting duct, how is urine?
urine is hyperosmotic to body fluids
what equip the kidneys of different vertebrates for osmoregulation in various habitats?
variations in nephron structure
how toxic is ammonia?
very; most toxic one
what is key in mammals?
water conservation
when an osmoregulator is in a hypoosmotic environment, what happens?
water goes into the cell and it swells or bursts
when an osmoregulator is in a hyperosmotic environment, what happens?
water goes out of the cell and it shrivels and/or dies
because solute concentration in sharks is somewhat higher than water, how does water enter?
water slowly enters the sharks body by osmosis and in food and is excreted urine or feces or specialized glands
euryhaline
withstand fairly large changes in environments -can be osmoconformers or osmoregulators
can animals be neither osmoregulators nor osmoconformers?
yup; they can be stenohaline or euryhaline