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

Insects use malpighian tubules

Animal Excretory Systems

Actively pump waste, extra salt and water into tubules

Rectum

Digestive tract

HindgutIntestine

Malpighiantubules

Rectum

Feces and urine

HEMOLYMPH

Reabsorption

Midgut(stomach)

Salt, water, and nitrogenous

wastes

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Animal Excretory Systems

Remaining waste excreted

Capillarynetwork

Components ofa metanephridium:

External opening

Coelom

Collecting tubule

Internal opening

Bladder

Worms use metanephridia

Collect body waste

10

Most urinary waste nitrogenous – from digesting protein

Vertebrate Urinary System

Blood filtered by kidneys

Fish excrete ammonia

Land vertebrates convert to urea – add to urine

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

Desert kangaroo rat – excretes very concentrated urine

Which excretory system produces the most concentrated excretion product?

1. protonephridia

2. malpighian tubules

3. metanephridia

4. kidneys

12

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

13

Micturition(urination)

Human Urinary System

Ureter

Bladder

Gotta pee?

Stretch stimulates contractions

Sphincters control release

14

Bladder

Ureter

Urogenital diaphragm

Internal urethralsphincter (involuntary)

External urethralsphincter (voluntary)

Human Urinary System - Bladder

15

Human Urinary System - Bladder

Sensory Input(spinal cord)

(-)

Stretch(~200 ml)

(-)

Brain

16

Urinary Disasters

Tycho Brahe: When you SHOULD go

The infamous candiru: When NOT TO go

17

renalartery

renalvein

ureter(cut away toshow path ofurine)

urinetobladder

renalcortex

renalmedulla

collectingduct

renalcortex

Bowman’scapsule

renalmedulla

loop ofHenle

Human Urinary System - Kidneys

Urine forms in the nephron, ~1 million/kidney

18

collecting duct

branch ofrenal arterybranch of

renal vein

Bowman’scapsule

glomerulus

Each nephron is a filter:

Glomerulus- network of capillaries

Bowman’s capsule- cup around glomerulus

Collecting duct- carries fluid from nephron

Human Urinary System - Kidneys

19

Human Urinary System - Kidneys

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

20

Human Urinary System - Kidneys

Reabsorption

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

21

Human Urinary System - Kidneys

• Loop of Henle – increasing

osmolarity from cortex to the medulla

– due to active transport of Na+, & Cl– at ascending loop

– reabsorption of water from descending loop and collecting duct

22

Human Urinary System - Kidneys

Secretion

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

23

Human Urinary System - Kidneys

Concentration

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

24

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

If a drug blocked Na+/Cl- cotransporters, what effect would this have on urine volume?

1. Increase volume, water would be retained

2. Decrease volume, water would be retained

3. Decrease volume, water would be excreted

4. Increase volume, water would be excreted

26

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

What effect would blocking ADH have?

1. Lots of dilute urine produced

2. Lots of concentrated urine produced

3. Minimal dilute urine produced

4. Minimal concentrated urine produced

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Urine: Waste and remaining water from nephron

• 95% water / 5% solutes (ions, urea)

Water Balance

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.