An albatross can drink
salt water – how can
they do this without
getting sick?!
1
Thought Questions:
If you eat a lot of salt,
what happens to your
urine?
If you do not drink
enough water, what
happens to your
urine?
If you drink excess
water, what happens
to your urine?
2
Lecture 12 Outline (Ch. 44)
I.
Homeostasis
II.
Water Balance
III. Animal Excretory Systems
IV. Human Urinary System
V.
I.
Bladder
II.
Kidneys
Water Control
VI. Preparation for next lecture
3
Urinary System
aka ‘Excretory System’
Maintains homeostasis of
body fluids via water balance
Osmolarity, (solute concentration
of solution), determines movement
of water across selectively
permeable membranes
4
Water Balance
Excrete
salt
ions
Gain water, salt from Osmotic water
ions from food gills
loss from gills,
body surface
Gain water,
salt ions from
seawater
Excrete salt ions &
little water in scanty
urine from kidneys
(a) Osmoregulation
in a saltwater fish
Uptake
water,
ions in
food
Uptake
salt ions
by gills
Osmotic
water
gain from
gills, body
surface
Excretion of large
amounts of dilute urine
(b) Osmoregulation
in a freshwater fish
5
Water Balance
Water
balance in a
kangaroo rat
(2 mL/day)
Ingested
in food (0.2)
Water
gain
(mL)
Water
balance in
a human
(2,500 mL/day)
Ingested
in food (750)
Ingested
in liquid
(1,500)
Derived from
metabolism (250)
Derived from
metabolism (1.8)
Feces (0.09)
Water
loss
(mL)
Urine
(0.45)
Evaporation (1.46)
Feces (100)
Urine
(1,500)
Evaporation (900)
6
Animal Excretory Systems
Simplest system
Nucleus
of cap cell
Cilia
Flame
bulb
Interstitial
fluid flow
Tubule
Tubules of
protonephridia
Opening in
body wall
Tubule cell
Flatworms use protonephridia
Wastes stored in excretory pore, drawn out by water
environment
7
Animal Excretory Systems
Digestive tract
Rectum
Intestine Hindgut
Midgut
(stomach)
Salt, water, and
nitrogenous
wastes
Malpighian
tubules
Feces and urine
Rectum
Reabsorption
Insects use
malpighian
tubules
Actively pump
waste,
extra salt
and water
into tubules
8
HEMOLYMPH
Animal Excretory Systems
Worms use metanephridia
Collect body waste
Coelom
Capillary
network
Components of
a metanephridium:
Internal opening
Collecting tubule
Bladder
External opening
Remaining waste excreted9
Vertebrate Urinary System
Most urinary waste nitrogenous –
from digesting protein
Desert kangaroo rat – excretes very
concentrated urine
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
10
Which excretory system produces the most
concentrated excretion product?
A.
B.
C.
D.
protonephridia
malpighian tubules
metanephridia
kidneys
Human Urinary System
1) Kidneys
• Blood w wastes brought
by renal artery to kidney
• Filtered blood carried
away by renal vein
left renal
artery
left kidney
left renal
vein
2) Ureters
• Transport urine away
from kidney
left ureter
3) Bladder
• Stores urine
• Max capacity ~ 1 L
4) Urethra
urinary
bladder
urethra
• Transport urine from
bladder to outside body
12
Human Urinary System
Micturition
(urination)
Ureter
Gotta pee?
Stretch stimulates
contractions
Sphincters control release
Bladder
13
Human Urinary System - Bladder
Ureter
Bladder
Internal urethral
sphincter (involuntary)
External urethral
sphincter (voluntary)
14
Human Urinary System - Bladder
Brain
Sensory Input
(spinal cord)
Stretch
(~200 ml)
(-)
(-)
15
Urinary Disasters
Tycho Brahe:
When you SHOULD go
The infamous candiru:
When NOT TO go
16
Human Urinary System - Kidneys
Urine forms in the nephron,
~1 million/kidney
renal
artery
renal
cortex
renal
medulla
renal
vein
ureter
(cut away to
show path of
urine)
collecting
duct
urine
renal
cortex
Bowman’s
capsule
loop of
Henle
renal
medulla
to
bladder
17
Human Urinary System - Kidneys
collecting duct
Each nephron is a filter:
Bowman’s
capsule
Glomerulus- network of
capillaries
glomerulus
Bowman’s capsule- cup
around glomerulus
Collecting duct- carries fluid
from nephron
branch of
renal vein
branch of
renal artery
18
Human Urinary System - Kidneys
Filtration
Water, nutrients, and wastes - filtered from
glomerulus into Bowman’s capsule
19
Human Urinary System - Kidneys
Reabsorption
In proximal
tubule, most
water and
nutrients are
reabsorbed
into blood.
20
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
21
Human Urinary System - Kidneys
Secretion
In distal tubule,
additional wastes
actively secreted
into the tubule
from the blood
22
Human Urinary System - Kidneys
Concentration
At collecting duct,
additional water
leaves, thus urine
more concentrated
than blood.
23
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
24
If a drug blocked Na+/Cl- cotransporters, what
effect would this have on urine volume?
A.
B.
C.
D.
Increase volume, water would be retained
Decrease volume, water would be retained
Decrease volume, water would be excreted
Increase volume, water would be excreted
Water Balance
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
26
What effect would blocking ADH have?
A.
B.
C.
D.
Lots of dilute urine produced
Lots of concentrated urine produced
Minimal dilute urine produced
Minimal concentrated urine produced
Water Balance
Urine: Waste and remaining water from nephron
• 95% water / 5% solutes (ions, urea)
Alcohol interferes with ADH
Production of dilute urine –
Dehydration
Headache
Fatigue
Nausea
28
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.