-Discussion questions-What is your fitness level?-Do you agree with the findings?-Why or why not?

Chapter 44: Osmoregulation and Excretion

1. What is osmoregulation? - How animals regulate solute concentrations &

balance the gain & loss of water2. What is excretion?

- How animals get rid of nitrogenous waste of metabolism3. What is the difference between an osmoregulator & an osmoconformer?

- Osmoconformer – does not actively adjust its internal osmolarity- Isoosmotic to environment- Marine animals

- Osmoregulator – actively controls osmolarity- NOT isoosmotic with environment

Figure 44.3 Osmoregulation in marine and freshwater bony fishes

Gain of water andsalt ions from foodand by drinkingseawater

Osmotic water lossthrough gills and other partsof body surface

Excretion ofsalt ionsfrom gills

Excretion of salt ionsand small amountsof water in scantyurine from kidneys

Uptake ofwater and someions in food

Osmotic water gainthrough gills and other partsof body surface

Uptake ofsalt ions by gills

Excretion oflarge amounts ofwater in dilute urine from kidneys

(a) Osmoregulation in a saltwater fish (b) Osmoregulation in a freshwater fish

- Hypoosmotic to ocean- loses LOTS of water at gills- “Drinks like a fish”- excretes salt & little urine

- Hyperosmotic to lake- gain LOTS of water at gills- LOTS of dilute urine

Chapter 44: Osmoregulation and Excretion

1. What is osmoregulation? 2. What is excretion?3. What is the difference between an osmoregulator & an osmoconformer?4. What is the biggest issue for land animals?

- Dehydration- Many adaptations to prevent this

5. What are the different nitrogenous waste products that animals excrete?- Ammonia- Urea- Uric acid

Figure 44.8 Nitrogenous wastes

Proteins Nucleic acids

Amino acids Nitrogenous bases

–NH2

Amino groups

Most aquaticanimals, includingmost bony fishes

Mammals, mostamphibians, sharks,some bony fishes

Many reptiles(includingbirds), insects,land snails

Ammonia Urea Uric acid

NH3 NH2

NH2

O C

C

CN

CO N

H H

C ONC

HN

OH

Ammonia – very soluble in water- VERY toxic- easily passes through membranes- 1 N at a time

Urea - 100,000X less toxic than –NH3

- -NH3 + CO2 in liver- helps conserve water- 2 N at a time

Uric acid- not very soluble in water- excreted in paste-like form- little water loss- stored in amniotic egg- 4 N at a time

Chapter 44: Osmoregulation and Excretion

1. What is osmoregulation? 2. What is excretion?3. What is the difference between an osmoregulator & an osmoconformer?4. What is the biggest issue for land animals?5. What are the different nitrogenous waste products that animals excrete?6. What are the 4 main functions of excretory systems?

- Filtration- Reabsorption- Secretion- Excretion

Figure 44.9 Key functions of excretory systems: an overview

Filtration. The excretory tubule collects a filtrate from the blood. Water and solutes are forced by blood pressure across the selectively permeable membranes of a cluster of capillaries and into the excretory tubule.

Reabsorption. The transport epithelium reclaims valuable substances from the filtrate and returns them to the body fluids.

Secretion. Other substances, such as toxins and excess ions, are extracted from body fluids and added to the contents of the excretory tubule.

Excretion. The filtrate leaves the system and the body.

Capillary

Excretorytubule

Filtra

teU

rine

1

2

3

4

Chapter 44: Osmoregulation and Excretion

1. What is osmoregulation? 2. What is excretion?3. What is the difference between an osmoregulator & an osmoconformer?4. What is the biggest issue for land animals?5. What are the different nitrogenous waste products that animals excrete?6. What are the 4 main functions of excretory systems?7. How have excretory systems evolved?

- Protonephridia – Planaria - Metanephridia – Earthworm- Malpighian tubules – insects - Kidney - us

Figure 44.10 Protonephridia: the flame-bulb system of a planarian

Nucleusof cap cell

Cilia

Interstitial fluidfilters throughmembrane wherecap cell and tubulecell interdigitate(interlock)

Tubule cell

Flamebulb

Nephridioporein body wall

TubuleProtonephridia(tubules)

Figure 44.11 Metanephridia of an earthworm

Nephrostome Metanephridia

Nephridio-pore

Collectingtubule

Bladder

Capillarynetwork

Coelom

Figure 44.12 Malpighian tubules of insectsDigestive tract

Midgut(stomach)

Malpighiantubules

Rectum

IntestineHindgut

Salt, water, and nitrogenous

wastes

Feces and urine Anus

Malpighiantubule

Rectum

Reabsorption of H2O,ions, and valuableorganic molecules

HEMOLYMPH

Chapter 44: Osmoregulation and Excretion

1. What is osmoregulation? 2. What is excretion?3. What is the difference between an osmoregulator & an osmoconformer?4. What is the biggest issue for land animals?5. What are the different nitrogenous waste products that animals excrete?6. What are the 4 main functions of excretory systems?7. How have excretory systems evolved?8. What is the structure and function of the kidney?

Figure 44.13 The mammalian excretory systemPosterior vena cava

Renal artery and vein

Aorta

Ureter

Urinary bladder

Urethra

(a) Excretory organs and major associated blood vessels

Juxta-medullarynephron

Corticalnephron

Collectingduct

To renalpelvis

Renalcortex

Renalmedulla

20 µm

(b) Kidney structure

Ureter

Kidney

Section of kidney from a rat

RenalmedullaRenalcortex

Renalpelvis

Afferentarteriolefrom renalartery

Glomerulus

Bowman’s capsuleProximal tubule

Peritubular capillaries

SEMEfferentarteriole fromglomerulus

Branch ofrenal vein

DescendinglimbAscendinglimb

Loopof

Henle

Vasarecta

Distal tubule

Collectingduct

(d) Filtrate and blood flow

(c) Nephron

Chapter 44: Osmoregulation and Excretion

1. What is osmoregulation? 2. What is excretion?3. What is the difference between an osmoregulator & an osmoconformer?4. What is the biggest issue for land animals?5. What are the different nitrogenous waste products that animals excrete?6. What are the 4 main functions of excretory systems?7. How have excretory systems evolved?8. What is the structure and function of the kidney?9. What is the structure & function of the nephron?

Chapter 44: Osmoregulation and Excretion1. What is osmoregulation? 2. What is excretion?3. What is the difference between an osmoregulator & an osmoconformer?4. What is the biggest issue for land animals?5. What are the different nitrogenous waste products that animals excrete?6. What are the 4 main functions of excretory systems?7. How have excretory systems evolved?8. What is the structure and function of the kidney?9. What is the structure & function of the nephron?

- Glomerulus – filtration due to BP- Proximal tubule – secretion & reabsorption- Loop of Henle

- Descending – reabsorption- Ascending – reabsorption

- Distal tubule – secretion & reabsorption- Collecting duct - reabsorption

Figure 44.14 The nephron and collecting duct: regional functions of the transport epithelium

Proximal tubule

Filtrate

H2OSalts (NaCl and others)HCO3

–

H+

UreaGlucose; amino acidsSome drugs

Key

Active transport

Passive transport

CORTEX

OUTERMEDULLA

INNERMEDULLA

Descending limbof loop ofHenle

Thick segmentof ascendinglimb

Thin segmentof ascendinglimbs

Collectingduct

NaCl

NaCl

NaCl

Distal tubule

NaCl Nutrients

Urea

H2O

NaClH2O

H2OHCO3 K+

H+ NH3

HCO3

K+ H+

H2O

1 4

32

3 5

Chapter 44: Osmoregulation and Excretion1. What is osmoregulation? 2. What is excretion?3. What is the difference between an osmoregulator & an osmoconformer?4. What is the biggest issue for land animals?5. What are the different nitrogenous waste products that animals excrete?6. What are the 4 main functions of excretory systems?7. How have excretory systems evolved?8. What is the structure and function of the kidney?9. What is the structure & function of the nephron?10. What causes the movement of water out of the filtrate?

- Increasing salt concentration within the kidney

Figure 44.15 How the human kidney concentrates urine

H2O

H2O

H2O

H2O

H2O

H2O

H2O

300

300 100

400

600

900

1200

700

400

200

100

Activetransport

Passivetransport

OUTERMEDULLA

INNERMEDULLA

CORTEX

1200

1200

900

600

400

300

600

400

300

Osmolarity of interstitial

fluid(mosm/L)

Figure 44.15 How the human kidney concentrates urine

H2O

H2O

H2O

H2O

H2O

H2O

H2O

Nacl

Nacl

Nacl

Nacl

Nacl

Nacl

Nacl

300

300 100

400

600

900

1200

700

400

200

100

Activetransport

Passivetransport

OUTERMEDULLA

INNERMEDULLA

CORTEX

1200

1200

900

600

400

300

600

400

300

Osmolarity of interstitial

fluid(mosm/L)

Figure 44.15 How the human kidney concentrates urine

H2O

H2O

H2O

H2O

H2O

H2O

H2O

Nacl

Nacl

Nacl

Nacl

Nacl

Nacl

Nacl

300

300 100

400

600

900

1200

700

400

200

100

Activetransport

Passivetransport

OUTERMEDULLA

INNERMEDULLA

CORTEX

H2OUrea

H2OUrea

H2O

Urea

H2O

H2O

H2O

H2O

1200

1200

900

600

400

300

600

400

300

Osmolarity of interstitial

fluid(mosm/L)

Chapter 44: Osmoregulation and Excretion1. What is osmoregulation? 2. What is excretion?3. What is the difference between an osmoregulator & an osmoconformer?4. What is the biggest issue for land animals?5. What are the different nitrogenous waste products that animals excrete?6. What are the 4 main functions of excretory systems?7. How have excretory systems evolved?8. What is the structure and function of the kidney?9. What is the structure & function of the nephron?10. What causes the movement of water out of the filtrate?11. How is blood osmolarity regulation?

- ADH- RAAS

Figure 44.16 Hormonal control of the kidney by negative feedback circuits

Osmoreceptorsin hypothalamus

Drinking reducesblood osmolarity

to set point

Increased Na+

and H2O reab-sorption in

distal tubules

Homeostasis:Blood pressure,

volume

STIMULUS:The juxtaglomerular

apparatus (JGA) respondsto low blood volume or

blood pressure (such as dueto dehydration or loss of

blood)

H2O reab-sorption helpsprevent further

osmolarity increase

STIMULUS:The release of ADH istriggered when osmo-receptor cells in the

hypothalamus detect anincrease in the osmolarity

of the blood

Homeostasis:Blood osmolarity

Hypothalamus

ADH

Pituitarygland

Increasedpermeability

Thirst

Aldosterone

Adrenal gland

Angiotensin II

Angiotensinogen

Reninproduction

Renin

Collecting duct

Distaltubule

Arterioleconstriction

Distal tubule

JGA

Antidiuretic hormone (ADH) enhances fluid retention by making the kidneys reclaim more water.

The renin-angiotensin-aldosterone system (RAAS) leads to an increase in blood volume and pressure.

(a) (b)