1

An albatross can drink salt water – how can they do this without getting sick?!

2

If you eat a lot of salt, what happens to your

urine?

Thought Questions:

If you do not drink enough water, what

happens to your urine?

If you drink excess water, what happens

to your urine?

3

Lecture 12 Outline (Ch. 44)

I. Homeostasis

II. Water Balance

III. Animal Excretory Systems

IV. Human Urinary System

I. Bladder

II. Kidneys

V. Water Control

VI. Preparation for next lecture

4

Maintains homeostasis of body fluids via water balance

aka ‘Excretory System’

Urinary System

Osmolarity, (solute concentration of solution), determines movement

of water across selectively permeable membranes

Hypoosmotic: lower solute conc, higher water

Hyperosmotic: higher solute conc, lower water

5

Excretesalt ionsfrom gills

Gain water, salt ions from food

Osmotic waterloss from gills,body surface

Excrete salt ions &little water in scanty urine from kidneys

Gain water, salt ions fromseawater

(a) Osmoregulation in a saltwater fish

Uptake water, ions in food

Uptakesalt ionsby gills

Osmotic watergain from gills, body surface

Excretion of largeamounts of dilute urine

(b) Osmoregulation in a freshwater fish

Water BalanceOsmoconformer: isoosmotic with surrounding

Osmoregulator: control internal osmoslarity

6

Watergain(mL)

Waterloss(mL)

Urine(0.45)

Urine(1,500)

Evaporation (1.46) Evaporation (900)

Feces (0.09) Feces (100)

Derived frommetabolism (1.8)

Derived frommetabolism (250)

Ingestedin food (750)

Ingestedin food (0.2)

Ingestedin liquid (1,500)

Waterbalance in akangaroo rat(2 mL/day)

Waterbalance ina human(2,500 mL/day)

Water Balance

7

Flatworms use protonephridia

Animal Excretory Systems

Simplest system

Wastes stored in excretory pore, drawn out by waterenvironment

Tubule

Tubules ofprotonephridia

Cilia

Interstitialfluid flow

Opening inbody wall

Nucleusof cap cell

Flamebulb

Tubule cell

8

Animal Excretory Systems

Remaining waste excreted

Capillarynetwork

Components ofa metanephridium:

External opening

Coelom

Collecting tubule

Internal opening

Bladder

Worms use metanephridia

Collect body waste

9

Most urinary waste nitrogenous – from digesting protein

Vertebrate Urinary System

Blood filtered by kidneys

Fish excrete ammonia (toxic at high levels)

Land vertebrates convert to urea – add to urine

To reduce water-loss, desert animals (reptiles, snakes, birds) excrete uric acid (non-toxic, hydrophobic)

Desert kangaroo rat – excretes very concentrated urine

10

urethra

left renalartery

left kidney

left renalvein

left ureter

urinarybladder

Human Urinary System1) Kidneys

• Blood w wastes brought by renal artery to kidney

• Filtered blood carried away by renal vein

2) Ureters• Transport urine away from kidney

3) Bladder• Stores urine

• Max capacity ~ 1 L

4) Urethra• Transport urine from bladder to outside body

11

Bladder

Ureter

Urogenital diaphragm

Internal urethralsphincter (involuntary)

External urethralsphincter (voluntary)

Human Urinary System - Bladder

Micturition(urination)

Gotta pee?

Stretch stimulates contractions

Sphincters control release

12

Human Urinary System - Bladder

Sensory Input(spinal cord)

(-)

Stretch(~200 ml)

(-)

Brain

13

Urinary Disasters

Tycho Brahe: When you SHOULD go

The infamous candiru: When NOT TO go

14

Human Urinary System - Kidneys

Urine forms in the nephron, ~1 million/kidney

Kidney Structure

Renalcortex

Renalmedulla

Renal artery

Renal vein

Ureter

Renal pelvis

nephron

Renalcortex

Renalmedulla

15

Each nephron is a filter:

Glomerulus- network of capillaries

Bowman’s capsule- cup around glomerulus

Loop of Henle-Tubule network for adjusting water, salt, and waste levels

Collecting duct- carries fluid from nephron

Human Urinary System - KidneysAfferent arteriolefrom renal artery Glomerulus

Bowman’s capsule

Proximaltubule

Peritubularcapillaries

Distaltubule

Efferentarteriolefrom glomerulus

Collectingduct

Branch ofrenal vein

Descendinglimb

Ascendinglimb

Loopof

Henle

16

Human Urinary System - Kidneys

FiltrationWater, nutrients, and wastes - filtered fromglomerulus into Bowman’s capsule

17

Human Urinary System - Kidneys

Reabsorption

In proximal tubule, most water along with bicarbonate, K+, and NaCl are reabsorbed into blood.

Proximal tubule Distal tubule

Filtrate

CORTEX

Loop ofHenle

OUTERMEDULLA

INNERMEDULLA

Key

Active transportPassive transport

Collectingduct

NutrientsNaCl

NH3

HCO3 H2O K

H

NaClH2O

HCO3

K H

H2ONaCl

NaCl

NaCl H2O

Urea

18

Human Urinary System - Kidneys

Proximal tubule Distal tubule

Filtrate

CORTEX

Loop ofHenle

OUTERMEDULLA

INNERMEDULLA

Key

Active transportPassive transport

Collectingduct

NutrientsNaCl

NH3

HCO3 H2O K

H

NaClH2O

HCO3

K H

H2ONaCl

NaCl

NaCl H2O

Urea

• Loop of Henle – increasing

osmolarity cortex to medulla

– active transport of Na+ & Cl– at ascending loop

19

Human Urinary System - Kidneys

Secretion

In distal tubule, additional wastes (like H+ and K+) are actively secreted into the tubule from the blood

Proximal tubule Distal tubule

Filtrate

CORTEX

Loop ofHenle

OUTERMEDULLA

INNERMEDULLA

Key

Active transportPassive transport

Collectingduct

NutrientsNaCl

NH3

HCO3 H2O K

H

NaClH2O

HCO3

K H

H2ONaCl

NaCl

NaCl H2O

Urea

20

Human Urinary System - Kidneys

Concentration

Proximal tubule Distal tubule

Filtrate

CORTEX

Loop ofHenle

OUTERMEDULLA

INNERMEDULLA

Key

Active transportPassive transport

Collectingduct

NutrientsNaCl

NH3

HCO3 H2O K

H

NaClH2O

HCO3

K H

H2ONaCl

NaCl

NaCl H2O

Urea

At collecting duct, additional water (and NaCl) leaves; urine more concentrated than blood.

21

Human Urinary System - Kidneys

Two-solute model:

NaCl and Urea are moved into the kidney medulla

The filtrate in the nephron passes into this area three times

Osmolarityof interstitial

fluid(mOsm/L)

Key

ActivetransportPassivetransport

INNERMEDULLA

OUTERMEDULLA

CORTEX H2O

H2O

H2O

H2O

H2O

H2O

H2O

1,200

1,200

900

600

400

300

NaCl

NaCl

H2O

H2O

H2O

H2O

H2O

H2O

H2O

Urea

Urea

Urea1,200

300

400

600

100

NaCl

NaCl

NaCl

NaCl

NaCl

NaCl

NaCl

100

200

400

700900

600

400

300

300300

ThirstHypothalamus

ADHPituitarygland

Osmoreceptors inhypothalamus trigger

release of ADH.

STIMULUS:Increase in blood

osmolarity (forinstance, after

sweating profusely)

Homeostasis:Blood osmolarity

(300 mOsm/L)

Drinking reducesblood osmolarity

to set point.

H2O reab-sorption helpsprevent further

osmolarityincrease.

Increasedpermeability

Distaltubule

Collecting duct

22

Body detects dehydration. Signal from hypothalamus to posterior pituitary.

Posterior pituitary releases ADH into the bloodstream.

ADH (antidiuretic hormone) allows more water reabsorbed into the blood.

Concentrated urine produced

Water Balance

23

Water Balance

Urine: Waste and remaining water from nephron

• 95% water / 5% solutes (ions, urea)

Alcohol interferes with ADH

Production of dilute urine – Dehydration

HeadacheFatigueNausea

Things To Do After Lecture 12…Reading and Preparation:

1. Re-read today’s lecture, highlight all vocabulary you do not understand, and look up terms.

2. Ch. 44 Self-Quiz: #1, 3, 4, 6(correct answers in back of book)

3. Read chapter 44, focus on material covered in lecture (terms, concepts, and figures!)

4. Skim next lecture.

“HOMEWORK” (NOT COLLECTED – but things to think about for studying):

1. Compare and contrast the four different types of excretory systems.

2. Diagram the nephron, labeling regions and describing uptake/excretion at each region.

3. Explain the parts of the human urinary system.

4. Discuss the role of ADH – location of secretion and effect.