Transcript Chap 25 – Excretory

Chapter 25
Control of Body Temperature
and Water Balance
PowerPoint Lectures for
Campbell Biology: Concepts & Connections, Seventh Edition
Reece, Taylor, Simon, and Dickey
© 2012 Pearson Education, Inc.
Lecture by Edward J. Zalisko
All organisms must EXTERNAL ENVIRONMENT
CO2
eliminate waste
O2 respiratory system
Food
Mouth
products!!
Eliminates CO2
ANIMAL
digestive
system
Digestive
eliminates system
solid
wastes
Nutrients
and excess H+.
Respiratory
system
Interstitial
fluid
Heart
Circulatory
system
Body
cells
Urinary
system
Intestine
Anus
Unabsorbed
matter (feces)
Metabolic waste
products (urine)
Functions of
the Excretory
System
-- Maintains
salt/water
balance
-- Eliminates
metabolic
wastes, drugs,
toxins
-- Indirect
regulation of
blood pressure
and pH
Osmoregulation = The Balance of water and
solute levels in body fluids.
 Osmoconformers (marine invertebrates)
– have body fluids with a [solute] = to [seawater]
 Osmoregulators (land animals, freshwater animals,
saltwater fish)
– have body fluids with [solute] that differ from environment
– must actively regulate water movement
Osmoregulation strategy depends on animal’s habitat!!
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Osmoregulation = Balance of solutes and water
 Freshwater fish
Passive water gain
through gills
Salts actively
Taken up by gills
–
gain water by osmosis
(mainly through gills),
–
take in salt by active
transport through their gills
and in food
–
excrete excess water in dilute
urine.
Excretion of dilute urine
from kidneys
FRESH WATER
(hypotonic environment)
Osmoregulation strategy depends on animal’s habitat!!
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Osmoregulation = Balance of solutes and water
 Saltwater fish
– lose water by osmosis from the gills and body surface,
– drink seawater, and
– use their gills and kidneys to excrete excess salt.
Passive loss of water through gills
Drinks seawater
SALT WATER
(hypertonic environment)
Salts actively
excreted by gills
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Excretion of
concentrated urine
Osmoregulation = Balance of solutes and water
 Land animals
– risk of dehydration
– lose water by evaporation and waste disposal
– gain water by drinking and eating
– conserve water by
– efficient kidneys.
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Disposal of Nitrogenous
and metabolic
wastes
 Metabolism produces
toxic by-products.
 Nitrogenous wastes =
breakdown products
of proteins and
nucleic acids.
 Animals dispose of
nitrogenous wastes in
different ways.
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The Human Urinary System
 The urinary
system
– forms and
excretes urine
and
– regulates
water and
solutes in
body fluids.
Nephrons = functional units of
kidneys
–extract a fluid filtrate from the
blood, and
–refine the filtrate to produce
urine.
Animation: Nephron Introduction
DETAILED STRUCTURE OF A NEPHRON
Processing of Urine in 4 Stages
 Filtration
– Blood enters kidney via renal artery --> various capillary beds
(GLOMERULUS)
– Each capillary bed wraps around nephron
– Blood filtered through capillary bed by force of blood pressure
– Proteins and RBCs remain in blood
– Filtrate contains: Water, salts, glucose, amino acids, urea collected
by Bowman’s capsule
From Bowman’s
Filtration
renal capsule
artery
Nephron tubule
H2O, other small molecules
Reabsorption
Secretion
Excretion
Urine
Interstitial fluid
Capillary
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To renal vein
Processing of Urine in 4 Stages
 Reabsorption
– proximal and distal tubules return
– Glucose, salt, and amino acids to blood by active transport
– Water follows by osmosis
 Secretion
– Substances in the blood are transported into the urine by active
transport at PCT and DCT
 Excretion
From Bowman’s
Filtration
renal capsule
artery
Nephron tubule
H2O, other small molecules
Reabsorption
Secretion
Excretion
Urine
Interstitial fluid
Capillary
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To renal vein
Processing of Urine
 Glomerulus
– Filters Urine by force of blood pressure
– Filtrate captured by Bowman’s Capsule
 PCT and DCT
– Active transport or secretion of substances to and from blood
 Loop of Henle
– Concentration of urine and reabsorption of water
– Active transport of Na out
– Water follows by osmosis
 Collecting Duct
– Further concentration of urine and reabsorption of water
– Responds to ADH
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PROXIMAL TUBULE
NaCl Nutrients
HCO3– H2O
K+
H+
NH3
CORTEX
DESCENDING
LIMB
OF LOOP OF
HENLE
Filtrate Contains:
H2O
Salts (NaCl and others)
HCO3–
H+
Urea
Glucose; amino acids
Some drugs
DISTAL TUBULE
H2O
NaCl
K+
H+
ASCENDING
LIMB OF LOOP
OF HENLE
NaCl
H2O
OUTER
MEDULLA
NaCl
COLLECTING
DUCT
Key
Active transport
Passive transport
HCO3–
Urea
NaCl
INNER
MEDULLA
H2O
Animation: Bowman’s Capsule and Proximal Tubule
Animation: Collecting Duct
Animation: Effect of ADH
Animation: Loop of Henle and Distal Tubule
Figure 25.8_1
Bowman’s
capsule
Proximal tubule
Nutrients H2O

NaCl HCO3
Blood
Cortex
Filtrate composition
H2O
Salts (NaCl
and others)
HCO3
H
Urea
Glucose
Amino acids
Some drugs
Some H
drugs
and poisons
Medulla
Reabsorption
Secretion
Filtrate movement
Figure 25.8_2
Proximal tubule
Nutrients H2O

NaCl HCO3
Cortex
1
Some H
drugs
and poisons
Distal tubule
H2O
NaCl HCO3
K H
3
Collecting
duct
Medulla
Interstitial
Loop of
fluid
Henle
2
NaCl
NaCl
H2O
NaCl
Urea
H2O
Reabsorption
Secretion
Filtrate
movement
Urine (to
renal pelvis)
Hormonal Control of
Kidneys
 Antidiuretic hormone
(ADH)
– Produced by pituitary
gland
Osmoreceptors
in hypothalamus
Thirst
Hypothalamus
Drinking reduces
blood osmolarity
to set point
ADH
Pituitary
gland
– Released in response to
decreased blood volume
– Regulates the permeability
of collecting duct to water
– High ADH; nephrons
reabsorb water from the
urine, returning it to the
blood
H2O reabsorption helps
prevent further
osmolarity
increase
STIMULUS
Increase in solute concentration
In blood; decrease blood
Collecting duct
Volume;
Decreased blood pressure
– Leads to increased blood
volume and blood
pressure
Homeostasis:
Proper blood pressure
Solute levels
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Kidneys and Acid-Base Balance
 pH is regulated by
– Secretion of acidic and basic organic compounds
– reabsorption of HCO3– and
– secretion of H+.
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