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