excretion ap biology unit 6 osmolarity osmolarity = total solute concentration of a solution which...

ExcretionExcretion

AP BiologyUnit 6

Osmolarity

• Osmolarity = total solute concentration of a solution

• Which way will the water move?

Slide 2 of 26

Question…

• What would happen if your body did not maintain proper osmolarity?

• You would either have an excess of water (bloated) or too little water (dehydrated)

• Cells wouldn’t have the correct balance of solutes and H2O won’t function properly

Slide 3 of 26

Osmoregulators versus Osmoconformers

Osmoconformers

• Animals whose internal osmolarity changes in relation to their external environment– There are limits to this– too high or too low

will cause death

• Marine invertebrates, sharks, rays

• Ex. Brine Shrimp (Artemia)

Slide 4 of 26

Osmoregulators

• Animals who can maintain their internal osmolarity at a particular level regardless of the external environment

• Ex. Fish, humans, lots of other animals

Slide 5 of 26

Question…

• How does the environment one lives in affect how osmoregulation takes place?– Depending on the environment one lives in,

osmoregulation can be very different

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Saltwater Fish• Challenge: Prevent too much water from

leaving the body (to go into the outside environment)– Higher osmolarity outside compared to inside

of body

• Solution…

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Freshwater Fish

• Challenge: Prevent too much water from coming into the body from the outside– Higher osmolarity inside body compared to

outside

• Solution…

Slide 8 of 26

• Land animals– face the risk of dehydration,– lose water by evaporation and waste disposal, – gain water by drinking and eating, and– conserve water by

• reproductive adaptations, • behavior adaptations,• waterproof skin, and• efficient kidneys.

What about land animals?

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What is Nitrogenous Waste?• Metabolic waste produced by

cells from the breakdown of Proteins and Nucleic Acids into NH2 groups

• This waste must be excreted

Slide 10 of 26

Figure 25.5

Proteins

Ammonia

Nitrogenous bases

NH2

(amino groups)

Nucleic acids

Urea

Uric acid

Mammals, mostamphibians, sharks,some bony fishes

Birds and many otherreptiles, insects, landsnails

Most aquatic animals,including most bonyfishes

Amino acids

What are the three major kinds of nitrogenous wastes?

• Ammonia: Most toxic. Only produced by aquatic animals

• Urea: Formed by combining Ammonia with CO2; Not as toxic; Released with less water

• Uric Acid: Least soluble; Excreted with the least amount of water

Slide 11 of 26

Excretion in Aquatic Animals

• For most aquatic animals, excreting ammonia is not an issue - why? – Ammonia is highly soluble in H2O, diffuses

away rapidly (won’t stay concentrated around them)

– Aquatic animals continuously lose ammonia from their bodies through diffusion across their gill membranes

Slide 12 of 26

Question…

• Why don’t terrestrial animals and some aquatic animals just excrete dilute ammonia in liquid? – Since ammonia is toxic even at fairly low

levels, it would have to use a lot of water to dilute it

– Too much water loss = dehydration

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Why do some land animals excrete uric acid instead of urea?

• Helps conserve H2O because it isn’t very soluble in water semi solid

• Ex. Birds, reptiles, insects, some amphibians

Slide 16 of 26

Figure 25.7

Reabsorption Secretion Excretion

Urine

To renal vein

Filtration

Nephron tubule

Capillary

Interstitial fluid

H2O, other small molecules

Bowman’s capsule

Fromrenalartery

Stages of Excretion

Excretory Process• Filtration: Initial movement of fluid and solutes

from the body

• Selective Reabsorption: Water and

desirable solutes are reabsorbed into the

body

• Secretion: Excess waste solute is added

to the filtrate

• Excretion: Modified filtrate is expelled

from the body

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Invertebrate: Flatworm Excretory System

• Protonephridia are tiny tubules that interstitial fluid moves through

• Filtrate is produced through the action of ciliated “flame bulb cells”

• Filtrate modified as it flows and exits through openings in the body wall

Slide 21 of 26

Invertebrate: Earthworms

• Due to pressure from blood water and solutes are pushed from the blood into the metanephridia

• Reabsorption and Secretion takes place between metanephridium and capillaries

• Stored urine excreted through external openings

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Vertebrates: What are the major organs of the urinary system?

• Kidneys – produce urine

• Ureters – carries urine from

the kidneys to bladder

• Bladder – stores urine

• Urethra – releases the urine

• Nephrons

– are the functional units of the kidneys,

– extract a fluid filtrate from the blood, and

– refine the filtrate to produce urine.

25.6 The urinary system plays several major roles in homeostasis

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NephronBlood Processing:1)Filtration: Arteries transport blood to the

kidney (nephron)Urea, water, Glucose, and

salts (minerals) are filtered out by diffusion/active transport

No!! Way too Big!!!

Will blood cells and proteins be filtered into the nephron?

NephronBlood Processing:2) Reabsorption: Substances still needed by the

body are removed from the filtrate and reenter the blood via diffusion/active transport

Ex: glucose, water, minerals (NOT urea)

Nephron

Blood Processing:

3)Secretion:Kidneys remove certain

substances from the blood and add them to the filtrate.

Ex: Salts, Water

Nephron

Blood Processing:

4)Excretion:Urine has been formed! Will

be moved to the bladder to be excreted from the body

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Animation: Nephron IntroductionRight click on animation / Click play

Figure 25.6

Aorta

Kidney

The urinary system

Inferiorvena cava

Renal artery (red)and vein (blue)

Ureter

Urethra

Urinary bladder

Renal cortex

Renal medulla

Renal pelvis

Ureter

The kidney

Proximal tubule

Bowman’s capsule

Tubule

Collectingduct

To renalpelvis

Branch ofrenal artery

Branch ofrenal vein

Renal cortex

Renal medulla

CapillariesGlomerulus

Distaltubule

Fromanothernephron

Bowman’s capsuleArteriole

from renalartery

Arteriolefrom glomerulus

Branch ofrenal vein

Loop of Henlewith capillarynetwork

Detailed structure of a nephron

1

3

2

Orientation of a nephron within the kidney

Collectingduct

Figure 25.6_1

Aorta

Kidney

The urinary system

Inferiorvena cava

Renal artery (red)and vein (blue)

Ureter

Urethra

Urinary bladder

Figure 25.6_2

Renal cortex

Renal medulla

Ureter

Renal pelvis

The kidney

Figure 25.6_3

Bowman’s capsule

Tubule

Collectingduct

To renalpelvis

Branch ofrenal artery

Branch ofrenal vein

Renal cortex

Orientation of a nephron within the kidney

Renal medulla

Figure 25.6_4

Proximal tubuleGlomerulus

DistaltubuleCollectingDuct

Fromanothernephron

Bowman’s capsule

Arteriolefrom renalartery

Arteriolefrom glomerulus

Branch ofrenal vein

Loop of Henlewith capillarynetwork

Detailed structure of a nephron

Capillaries

1

3

2

25.7 Overview: The key processes of the urinary system are filtration, reabsorption, secretion,

and excretion

• Filtration– Blood pressure forces water and many small

molecules through a capillary wall into the start of the kidney tubule.

• Reabsorption– refines the filtrate,– reclaims valuable solutes (such as glucose,

salt, and amino acids) from the filtrate, and– returns these to the blood.

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Figure 25.7_1

Filtration

Nephron tubule

Capillary

Interstitial fluid

H2O, other small molecules

Bowman’s capsule

Fromrenalartery

Figure 25.7_2

Reabsorption Secretion Excretion

Urine

To renal veinCapillary

Nephron tubule

• Substances in the blood are transported into the filtrate by the process of secretion.

• By excretion the final product, urine, is excreted via the ureters, urinary bladder, and urethra.

25.7 Overview: The key processes of the urinary system are filtration, reabsorption, secretion,

and excretion

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Figure 25.7

Reabsorption Secretion Excretion

Urine

To renal vein

Filtration

Nephron tubule

Capillary

Interstitial fluid

H2O, other small molecules

Bowman’s capsule

Fromrenalartery

• Reabsorption in the proximal and distal tubules removes– nutrients,– salt, and– water.

• pH is regulated by– reabsorption of HCO3

– and

– secretion of H+.

25.8 Blood filtrate is refined to urine through reabsorption and secretion

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• High NaCl concentration in the medulla promotes reabsorption of water.

25.8 Blood filtrate is refined to urine through reabsorption and secretion

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Animation: Bowman’s Capsule and Proximal TubuleRight click on animation / Click play

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Animation: Collecting DuctRight click on animation / Click play

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Animation: Effect of ADHRight click on animation / Click play

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Animation: Loop of Henle and Distal TubuleRight click on animation / Click play

Figure 25.8 Bowman’scapsule

Blood

Nutrients H2ONaCl

Proximal tubule

Somedrugsand poisonsCortex

Medulla

Interstitialfluid Loop of

Henle

H2O

Filtrate composition

Reabsorption

Filtrate movement

Secretion

Distal tubule1

2 NaCl

NaCl

NaCl

UreaH2O

3K

H

Collectingduct

Urine (torenal pelvis)

H2ONaCl HCO3

H2O

Salts (NaCl and others) HCO3

H

Urea Glucose Amino acids Some drugs

HCO3

H

Figure 25.8_1

Blood

Filtrate composition

Reabsorption

Filtrate movement

Secretion

Bowman’scapsule

Nutrients H2ONaCl HCO3

Proximal tubule

Somedrugsand poisonsCortex

Medulla

H

H2O

Salts (NaCl and others) HCO3

H

Urea Glucose Amino acids Some drugs

Figure 25.8_2

Reabsorption

Filtrate movement

Secretion

NutrientsNaCl HCO3

Somedrugsand poisonsCortex

Medulla

Proximal tubule

Interstitialfluid Loop of

Henle

H2O

NaCl

NaCl

NaCl

UreaH2O

Collectingduct

Urine (torenal pelvis)

Distal tubuleH2O

NaCl HCO3

1

3

2

H2O

H HK

• Antidiuretic hormone (ADH) regulates the amount of water excreted by the kidneys by– signaling nephrons to reabsorb water from the

filtrate, returning it to the blood, and– decreasing the amount of water excreted.

• Diuretics– inhibit the release of ADH and– include alcohol and caffeine.

25.9 Hormones regulate the urinary system

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